Promoting the conservation and use of underutilized and neglected crops. 17.
and J. Tous
Ceratonia siliqua L.
2 Carob tree.
The International Plant Genetic Resources Institute (IPGRI) is an autonomous international
scientific organization operating under the aegis of the Consultative Group on International
Agricultural Research (CGIAR). The international status of IPGRI is conferred under an
Establishment Agreement which, by March 1997, had been signed by the Governments of
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Morocco, Pakistan, Panama, Peru, Poland, Portugal, Romania, Russia, Senegal, Slovak
Republic, Sudan, Switzerland, Syria, Tunisia, Turkey, Uganda and Ukraine. IPGRI’s mandate
is to advance the conservation and use of plant genetic resources for the benefit of present and
future generations. IPGRI works in partnership with other organizations, undertaking
research, training and the provision of scientific and technical advice and information, and has
a particularly strong programme link with the Food and Agriculture Organization of the United
Nations. Financial support for the research agenda of IPGRI is provided by the Governments
of Australia, Austria, Belgium, Canada, China, Denmark, Finland, France, Germany, India,
Italy, Japan, the Republic of Korea, Luxembourg, Mexico, the Netherlands, Norway, the
Philippines, Spain, Sweden, Switzerland, the UK and the USA, and by the Asian Development
Bank, CTA, European Union, IDRC, IFAD, Interamerican Development Bank, UNDP and the
The Institute of Plant Genetics and Crop Plant Research (IPK) is operated as an
independent foundation under public law. The foundation statute assigns to IPK the task
of conducting basic research in the area of plant genetics and research on cultivated plants.
The geographical designations employed and the presentation of material in this
publication do not imply the expression of any opinion whatsoever on the part of IPGRI, the
CGIAR or IPK concerning the legal status of any country, territory, city or area or its
authorities, or concerning the delimitation of its frontiers or boundaries. Similarly, the views
expressed are those of the authors and do not necessarily reflect the views of these
Batlle, I. and J. Tous. 1997. Carob tree. Ceratonia siliqua L. Promoting the conservation and
use of underutilized and neglected crops. 17. Institute of Plant Genetics and Crop Plant
Research, Gatersleben/International Plant Genetic Resources Institute, Rome, Italy.
Via delle Sette Chiese 142 Corrensstrasse 3
00145 Rome 06466 Gatersleben
© International Plant Genetic Resources Institute, 1997
Promoting the conservation and use of underutilized and neglected crops. 17. 3
1 Introduction 7
2 Names of the species and taxonomy 9
3 Botanical description 10
4 Reproductive biology 14
5 Origin and centres of diversity 20
5.1 Origin 20
5.2 Distribution 20
5.3 Domestication 21
6 Properties 23
7 Uses 26
8 Genetic resources 30
8.1 Existing genetic variation 30
8.2 Conservation 38
9 Genetic improvement 43
9.1 Breeding objectives 43
9.2 Breeding methods 43
10 Production areas 45
11 Ecology 48
11.1 Climate requirements 49
11.2 Soil requirements 49
11.3 Water requirements 49
12 Agronomy 50
12.1 Propagation 50
12.2 Orchard design 54
12.3 Pollination 54
12.4 Training systems and pruning 55
12.5 Fertilization 57
12.6 Irrigation 57
12.7 Soil maintainance 58
12.8 Pests and diseases 58
12.9 Yield 59
12.10 Harvesting 60
12.11 Processing 61
13 Limitations of the crop 63
13.1 Cold-hardiness 63
13.2 Suitability for modern orchards 63
13.3 Market situation 63
14 Prospects 64
15 Research needs 67
4 Carob tree.
16 References 70
Appendix I. Cultivar description 79
Appendix II. Centres of research and genebanks 88
Appendix III. Basic descriptor list for carob 91
Promoting the conservation and use of underutilized and neglected crops. 17. 5
Humanity relies on a diverse range of cultivated species; at least 6000 such species are
used for a variety of purposes. It is often stated that only a few staple crops produce
the majority of the food supply. This might be correct but the important contribution
of many minor species should not be underestimated. Agricultural research has
traditionally focused on these staples, while relatively little attention has been given
to minor (or underutilized or neglected) crops, particularly by scientists in developed
countries. Such crops have, therefore, generally failed to attract significant research
funding. Unlike most staples, many of these neglected species are adapted to various
marginal growing conditions such as those of the Andean and Himalayan highlands,
arid areas, salt-affected soils, etc. Furthermore, many crops considered neglected at
a global level are staples at a national or regional level (e.g. tef, fonio, Andean roots
and tubers, etc.), contribute considerably to food supply in certain periods (e.g.
indigenous fruit trees) or are important for a nutritionally well-balanced diet (e.g.
indigenous vegetables). The limited information available on many important and
frequently basic aspects of neglected and underutilized crops hinders their
development and their sustainable conservation. One major factor hampering this
development is that the information available on germplasm is scattered and not
readily accessible, i.e. only found in ‘grey literature’ or written in little-known
languages. Moreover, existing knowledge on the genetic potential of neglected crops
is limited. This has resulted, frequently, in uncoordinated research efforts for most
neglected crops, as well as in inefficient approaches to the conservation of these
This series of monographs intends to draw attention to a number of species
which have been neglected in a varying degree by researchers or have been
underutilized economically. It is hoped that the information compiled will
contribute to: (1) identifying constraints in and possible solutions to the use of the
crops, (2) identifying possible untapped genetic diversity for breeding and crop
improvement programmes and (3) detecting existing gaps in available conservation
and use approaches. This series intends to contribute to improvement of the
potential value of these crops through increased use of the available genetic
diversity. In addition, it is hoped that the monographs in the series will form a
valuable reference source for all those scientists involved in conservation, research,
improvement and promotion of these crops.
This series is the result of a joint project between the International Plant Genetic
Resources Institute (IPGRI) and the Institute of Plant Genetics and Crop Plant
Research (IPK). Financial support provided by the Federal Ministry of Economic
Cooperation and Development (BMZ) of Germany through the German Agency for
Technical Cooperation (GTZ) is duly acknowledged.
Dr Joachim Heller, Institute of Plant Genetics and Crop Plant Research (IPK)
Dr Jan Engels, International Plant Genetic Resources Institute (IPGRI)
Prof. Dr Karl Hammer, Institute of Plant Genetics and Crop Plant Research (IPK)
6 Carob tree.
The information contained in this book has been compiled by the authors since 1984
when work on carob was started at IRTA-Mas Bové. We acknowledge gratefully
the support received from the Institut de Recerca i Tecnologia Agroalimentàries
(IRTA) to carry out this work. A survey of the Catalonian genetic resources
supported by the Diputació de Tarragona was undertaken in 1984 and followed by
a research project on Spanish cultivar characterization (1985-88) funded by the
Comisión de Investigación Científica y Técnica (CICYT). Since 1988, IRTA and the
Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) of
the Spanish Ministry of Agriculture, Fisheries and Food (MAPA) and some private
firms have financed the work on carob at IRTA. The carob germplasm collection
at IRTA is also funded by INIA.
We are very grateful to Mr K.R. Tobutt for thorough and critical review of the
draft. His many valuable comments and suggestions have greatly improved this
monograph. We also thank Dr J. Heller and Prof. Dr F.G. Crescimanno for their
critical and useful review of the draft. We are indebted to our colleagues at the
Departament d’Arboricultura Mediterrània of IRTA for many useful discussions
and help, particularly to Mr F.J. Vargas for supporting the work and to Mr A.
Romero, Dr M. Rovira and Mr J. Plana for their helpful collaboration on many tasks
of the carob programme. The first author is grateful for a scholarship from the
Catalan Comissió Interdepartamental de Recerca i Innovació Tecnològica (CIRIT)
during his stay in 1987 at Istituto di Coltivazioni Arboree, University of Palermo
and also for the warm welcome he received there.
I. Batlle and J. Tous
10 April 1997
Promoting the conservation and use of underutilized and neglected crops. 17. 7
The carob tree has been grown since antiquity in most countries of the
Mediterranean basin, usually in mild and dry places with poor soils. Its value was
recognized by the ancient Greeks, who brought it from its native Middle East to
Greece and Italy, and by the Arabs, who disseminated it along the North African
coast and north into Spain and Portugal. It was spread in recent times to other
Mediterranean-like regions such as California, Arizona, Mexico, Chile and
Argentina by Spaniards, to parts of Australia by Mediterranean emigrants and to
South Africa and India by the English.
The carob tree is an important component of the Mediterranean vegetation and
its cultivation in marginal and prevailing calcareous soils of the Mediterranean
region is important environmentally and economically. Traditionally, grafted carob
trees have been interplanted with olives, grapes, almonds and barley in low-
intensity farming systems in most producing countries. Carob pods with their
sugary pulp are a staple in the diet of farm animals and are eaten by children as
snacks or by people in times of famine. However, currently the main interest is seed
production for gum extraction. Kibbled pods have been shipped from producing
countries to all over Europe. Because of low orchard management requirements
the carob tree is suitable for part-time farming and shows potential for planting in
semi-arid Mediterranean or subtropical regions. The trees are also useful as
ornamentals and for landscaping, windbreaks and afforestation. Cattle can browse
on leaves and the wood is suitable for fuel.
World production is estimated at about 310 000 t/year produced from some 200
000 ha with very variable yields depending on cultivar, region and farming practice.
Spain is the leading carob producer, producing on average 135 000 t/year (MAPA
1994), followed by Italy, Portugal, Morocco, Greece, Cyprus, Turkey, Algeria and
some other countries. A full account of the main carob-producing areas is presented
in section 10.
Carob has been neglected with respect to both cultural practices and research
and development. Apart from a few classic works written by interested scientists
like Rullán and Estelrich (1882), Bassa (1896) and Lleó (1901) in Spain, Pereira (1900)
and Da Matta (1952) in Portugal, Russo (1954) in Italy, Mitrakos (1988) in Greece,
Orphanos and Papaconstantinou (1969) in Cyprus, and various reports especially
from Israel (Goor et al. 1958) and the United States (Condit 1919), references on this
crop are scarce. We have tried to review most of the work published over the last
100 years and make useful information available to producers, processors,
students, scientists and amateurs.
The information presented in this publication has been compiled within the
context of the carob Research & Development programme conducted at IRTA-Mas
Bové since 1984; this has two main aims. The first was to collect and study the
genetic resources available in the Mediterranean region and other production areas
– IRTA’s carob germplasm collection is the widest in the world with over 90
introductions under evaluation. The second aim was to assess the potential yield
8 Carob tree.
of this crop when grown in modern orchards with minimum management – a
nonirrigated trial in Tarragona, Spain, with 12% of pollinators andwith 500 mm of
annual rainfall, is yielding about 5000 kg/ha of pods 10 years after planting.
This monograph describes the genetic resources of carob (Ceratonia siliqua L.)
and reviews various aspects of its taxonomy, botany, origin, ecology, properties,
uses, diversity and breeding. In addition, a full account of the crop production
areas, agronomy, limitations, market, prospects and research needs is presented.
An important scope of this work is to contribute to the conservation of the diversity
of the cultivated carob and wild relatives. Thus exchange of information as well
as germplasm is made possible. The authors hope that the thriving features, current
situation of the genetic resources, potential prospects and research needs of carob
as a plant and crop for Mediterranean regions are clearly presented.
Promoting the conservation and use of underutilized and neglected crops. 17. 9
2 Names of the species and taxonomy
The scientific name of carob tree (Ceratonia siliqua L.) derives from Greek keras, horn,
and Latin siliqua, alluding to the hardness and shape of the pod. The common name
originates from the Hebrew kharuv, from which are derived the Arabic kharrub and
later algarrobo or garrofero in Spanish, carrubo in Italian, caroubier in French,
Karubenbaum in German, alfarrobeira in Portuguese, charaoupi in Greek, charnup in
Turkish, and garrofer or garrover in Catalan. Various names are used in different
regions of Italy: ascenedda, soscella (Basilicata); carrua, carrubbi (Sicilia); carruba,
sciuscella (Campania); carrubbio, carrubo, cornola, corue, pselocherato, pselocherea
(Puglia); suscella (Campania and Puglia); and garrubaro, garrubbo (Calabria) (Hammer
et al. 1992). In Asia the following names are used: chiao-tou-shu (China), gelenggang
(Malaysia) and chum het tai (Thailand) (Kruse 1986). The carob is also known as St.
John’s bread or locust bean in reference to the presumed use of its ‘locusts’ as food
by St. John the Baptist and, from that derives Johannisbrotbaum in German. Jewellers
used its uniform seeds as a unit of weight (200 mg), the carat.
The genus Ceratonia belongs to the family Leguminosae (syn. Fabaceae) of the
order Rosales. Legumes are important members of tropical, subtropical and
temperate vegetation throughout the world. This is one of the largest families of
flowering plants and includes 650 genera and over 18 000 species (Polhill et al. 1981)
and is extremely variable in morphology and ecology. The carob tree is generally
placed in the tribe Cassieae of the subfamily Caesalpinioideae; however, several
authors doubt Ceratonia’s position in the Cassieae (Irwin and Barneby 1981; Tucker
1992a, 1992b). The diploid chromosome number for Ceratonia is 2n=24 whereas
many members of the Cassieae complex have 2n=48 (Goldblatt 1981). The genus
Ceratonia is regarded as one of the most archaic of the legume genera (Tucker 1992a).
Taxonomically, Ceratonia is completely isolated from all other genera of its family
(Zohary 1973). Hillcoat et al. (1980) and Tucker (1992a) considered the carob as a
very isolated remnant of a part of the family Leguminosae now largely extinct.
A second species of Ceratonia – C. oreothauma Hillcoat, Lewis and Verdc. – was
only described in 1980. Two subspecies were distinguished: subsp. oreothauma,
native to Arabia (Oman), and subsp. somalensis, native to the north of Somalia.
Ceratonia oreothauma is very distinct morphologically from C. siliqua. In addition, C.
oreothauma has slightly smaller pollen grains than C. siliqua and they are tricolporate
rather than tetracolporate (Ferguson 1980). As pollen grains are more evolved than
tricolporate grains, C. oreothauma was suggested as the wild ancestor of the
cultivated C. siliqua by Hillcoat et al. (1980).
1 0 Carob tree.
3 Botanical description
The carob tree grows as a sclerophyllous evergreen shrub or tree up to 10 m high,
with a broad semispherical crown and a thick trunk with brown rough bark and
sturdy branches (Fig. 1). Leaves are 10-20 cm long, alternate, pinnate, with or
without a terminal leaflet. Leaflets are 3-7 cm long, ovate to elliptic, in 4-10
normally opposite pairs, coriaceous, dark green and shiny above, pale green
beneath and finely veined with margins slightly ondulate, and tiny stipules. The
leaves are sclerophyllous and have a very thick single-layered upper epidermis, the
cells of which contain phenolic compounds in the large vacuoles, and stomata are
present only in the lower epidermis and arranged in clusters (Mitrakos 1988).
Relevant parts of the plant are shown in Figure 2. Carob does not shed its leaves
in the autumn but only in July every second year, and it only partially renews leaves
in spring (April and May) (Diamantoglou and Mitrakos 1981).
The carob is a dioecious species with some hermaphroditic forms; thus male,
female and hermaphrodite flowers are generally borne on different trees.
Unisexual and bisexual flowers are rare in the inflorescence. The flowers are
initially bisexual, but usually one sex is suppressed during late development of
functionally male or female flowers (Tucker 1992a); dioecy is not common among
Leguminosae. In evolutionary terms, unisexuality is generally regarded as a
derived character from bisexual ancestral state.
Fig. 1. Carob tree growing in Seville, Andalusia, Spain.
Promoting the conservation and use of underutilized and neglected crops. 17. 11
Fig. 2. Shoots, leaves, leaflets, male and female inflorescences and pods (from Zohary 1973,
reprinted with permission).
1 2 Carob tree.
Flowers are small and numerous, 6-12 mm long, spirally arranged along the
inflorescence axis in catkin-like racemes borne on spurs from old wood and even on
the trunk (cauliflory). Flowers are green-tinted red. Flowers show pentamerous
symmetry with calyx but not corolla placed on a short pedicel. The calyx is disc-
shaped, reddish-green and bears nectaries. Female flowers consist of a pistil (6-8.5
mm) on a disk and rudimentary stamens, surrounded by 5 hairy sepals. The ovary
is bent, consisting of two carpels 5-7 mm long and containing several ovules. The
stigma has 2 lobes. Male flowers consist of a nectarial disk with 5 stamens with
delicate filaments surrounded by hairy sepals. In the centre of the disk there is a
rudimentary pistil. Hermaphrodite flowers are a combination of both types,
containing a pistil and a complement of 5 stamens. Pollen grains released from the
anthers are of spheroidal shape and are tetracolpate (Ferguson 1980). Pollen
diameter is 28-29 µm at the poles and 25-28 µm at the equator (Ferguson 1980;
Linskens and Scholten 1980).
The fruit is an indehiscent pod, elongated, compressed, straight or curved,
thickened at the sutures, 10-30 cm long, 1.5-3.5 cm wide and about 1 cm thick with
blunt or subacute apex (Fig. 3). Pods are brown with a wrinkled surface and are
leathery when ripe. The pulp comprises an outer leathery layer (pericarp) and softer
inner region (mesocarp). Seeds occur in the pod transversally, separated by mesocarp
(Fig. 3). They are very hard and numerous, compressed ovate-oblong, 8-10 mm long,
7-8 mm wide and 3-5 mm thick; the testa is hard and smooth, glossy brown, the hilum
The haploid chromosome number of Ceratonia is n=12 and differs from other
Cassieae (base number n=14) according to Goldblatt (1981), who suggested it might
Promoting the conservation and use of underutilized and neglected crops. 17. 13
Fig. 3. Important parts of the carob pod (A), section of pod (B) and seed (C).
1 4 Carob tree.
4 Reproductive biology
Many basic aspects of carob reproductive biology, such as floral biology, pollination
compatibility between different sexual types and also cultivars, and flowering and
fruiting phenology remain largely unknown. However, progress has been made
by McLean Thompson (1944), Russo (1954), Schroeder (1959), Meikle (1977),
Leshem and Ophir (1977), Haselberg (1988), Passos de Carvalho (1988), Linskens
and Scholten (1980), Retana et al. (1990, 1994), Bosch et al. (1996), Ortiz et al. (1996)
and Rovira and Tous (1996). In carob, Condit (1919) reported the tree ratio of
female to male is about 50:50 including a few hermaphrodites.
Floral morphology of carob is complex. Meikle (1977), from literature and
observed specimens in Cyprus, summarized five types of inflorescences:
• male, the flowers having long filaments and abortive pistils
• male, the flowers having short filaments and abortive pistils
• hermaphrodite, the flowers having fully developed stamens and pistils
• female inflorescences, the flowers with abortive staminodes and fully
• polygamous inflorescences, some of the flowers male, some female and
Schroeder (1959) grouped into five floral classes 59 carob cultivars growing in
California based on the expression of their sex throughout the season. The five
groups were: pistillate, pistillate with occasional perfect flowers, perfect with
occasional staminate flowers, perfect and staminate. He reported that while adult
trees maintained their floral types, young trees showed variation in the
development of stamens. The provision of pollinators will prove to be essential for
cultivars in the first three groups in order to ensure adequate commercial fruit set.
He also noted that cultivars that were hermaphrodite early in the season showed
some tendency toward pistil development failure later in the season.
A simple carob inflorescence type classification would be:
• male inflorescences (Fig. 4a)
• female inflorescences (Fig. 4b)
• hermaphrodite inflorescence (Fig. 4c).
Hillcoat et al. (1980) reported from the available material of C. oreothauma that
flowers are either purely male or female with minute, completely sterile, primary
anthers. Thus variation in sexuality and morphology of flowers of this species is
not as wide as in the cultivated carob.
It is difficult to find carob trees of all flower types in naturalized populations
of the same area. In the Mediterranean Spanish coast, female and male types are
common and hermaphrodite forms rare. However, hermaphrodites are more
frequently observed in the Eastern coast of Spain than in the South or in the Algarve
in Portugal (Batlle and Tous 1994). In the Balearic Islands the frequency of
hermaphrodites is higher than in the Iberian peninsula.
There are many different forms of males, but the two main types observed in
Italy, Portugal and Spain are often locally named after their anther colour as ‘Red’
Promoting the conservation and use of underutilized and neglected crops. 17. 15
Fig. 4. Male inflorescence (a), female flowers and pods (b) and hermaphrodite flowers (c).
1 6 Carob tree.
or ‘Yellow’. This feature has proven to be insufficient for their classification as it
is determined independently of other flower characteristics (Haselberg 1988). It
appears that blooming of ‘Red’ males is more extended than that of ‘Yellow’ males.
The carob is the only Mediterranean tree with the main flowering season in
autumn (September-November), similar to many truly tropical plants. However,
the time and length of the flowering period depends on local climatic conditions as
in most fruit and nut trees. In very hot places male and female trees have been
observed in full bloom during June (Leshem and Ophir 1977). Its blooming period
in some places overlaps partially with that of the loquat tree (Eriobotrya japonica).
The extended flowering season in carob compensates for the unstable weather at
that time of the year, and ensures that at least some flowers will be pollinated in
a spell of good weather and insect activity. Ceratonia oreothauma flowers in March
and April in its native places in which was first reported (Hillcoat et al. 1980). Thus
hybridization between both species is only feasible artificially.
Pollen transport from staminate to pistillate flowers is effected by insects,
mainly bees, flies, wasps and night-flying moths (Retana et al. 1990, 1994; Ortiz et
al. 1996) but also by wind (Passos de Carvalho 1988; Tous and Batlle 1990). Flowers
of all three sexes secrete nectar, though volume of nectar and sugar content is higher
in female flowers than in male (Ortiz et al. 1996). Male and hermaphrodite flowers
emit a semen-like odour which attracts insects. Different insect groups tend to visit
flowers at different hours. Bees are scarce in autumn when carobs are blooming,
both in number of species and individuals. How far windborne pollen is effective
is unknown, but isolated female trees have produced light crops. Currently, the
role of the wind on carob pollen transport is being re-emphasized (Martins-Louçâo
et al. 1996a).
The developmental stages of both female and male flowers are six and five,
respectively, and were first defined and described by Haselberg (1988) (Fig. 5).
Flowering and fruiting phenology of some male, female and hermophrodite
cultivars have been studied by Retana et al. (1994) and Bosch et al. (1996).
Development of inflorescences is more protracted in female and hermaphrodite
cultivars (2 months or more) than in male ones (1-1.5 months). So two Spanish
female cultivars (‘Negret’ and ‘Rojal’) bear inflorescences in as many as six
developmental stages, whereas ‘Red’ and ‘Yellow’ male trees never carry
inflorescences of more than four developmental stages (Retana et al. 1994).
Ferguson (1980) reported up to 36% of morphologically abnormal pollen grains
in male plants of carob, although this appeared to be unrelated to a reduction in
pollen fertility. Sfakiotakis (1978) observed high pollen germination variability in
vitro among wild male trees in Crete, their germination percentages ranging from
4.3 to 69%. However, Ciampolini et al. (1986) found less difference in pollen
germinability: from 5.2 to 38.6% in males and from 7.1 to 26% in hermaphrodite
types. Some pollen abnormality also occurred in C. oreothauma (Ferguson 1980).
Leshem and Ophir (1977) reported higher levels of endogenous giberellins in
the leaves and inflorescences of female than of male carob trees. In addition, they
Promoting the conservation and use of underutilized and neglected crops. 17. 17
Fig. 5. Stages of development of female (F) and male (M) flowers of carob (from Haselberg 1988,
1 8 Carob tree.
observed that the switch from vegetative to generative growth in both the male and
the female may be associated with a low concentration of endogenous gibberellins
in June in a multi-hormone complex (auxin, ethylene, etc.) presumably needed for
flower induction. They also found that vegetative spring growth is related to
enhanced giberellin activity. Although physiological differences between male and
female trees have been described, further research is needed.
Female and hermaphrodite inflorescences carry a mean of 17 and 20 flowers,
respectively, but few produce a pod and only a small proportion of inflorescences
set more than two fruits (Retana et al. 1994). Bosch et al. (1996) found low pod
initiation (from 12 to 38%) of ‘Negra’ and ‘Rojal’ flowers. The overall fruit set is
normally around 3-5% in Italian, Portuguese or Spanish cultivars (Russo 1954;
Haselberg 1988; Rovira and Tous 1996). Bosch et al. (1996) observed fruit set to be
from 1 to 11% in two consecutive years. Haselberg (1996) observed fruit set of 1%
and even 0.05% in years of profuse blooming in ‘Mulata’. Haselberg (1996) found
a positive correlation between flower intensity and fruit drop and also that pods
with a low number of seeds aborted more frequently.
Shedding of carob flowers and young fruits occurs mainly from October to
December, then slows down during January-February and rarely occurs from June
to early August (Bosch et al. 1996; Rovira and Tous 1996). Bosch et al. (1996)
observed pod shedding of 59-90% and that it takes place mainly in spring. They
reported that on larger inflorescences of the two female cultivars, higher rates of
fruit initiation, fruit set and seed set per flower occurred than on smaller
inflorescences. Haselberg (1996) reported that variations in flowering intensity
and pod yield are likely to be more influenced by endogenous factors related to
alternate bearing than by climatic conditions. However, unfavourable
environmental conditions may significantly reduce yield by fruit set reduction,
thus increasing production risk in marginal growing sites.
Ilahi and Vardar (1976) determined that carob pod development follows a
sigmoidal growing curve like many other fruits (Fig. 6) and could be divided into
three stages. During stage I (slow growth), after fertilization in October and during
autumn and winter, the bean shows hardly any weight (fresh and dry) increase.
Stage II (fast growth) starts at the beginning of spring when the pod enters an active
period of growth (April to June). In stage III the fruit grows slowly, ripens and
starts becoming dry in June and changes colour from green to brown. Bosch et al.
(1996) reported a similar pattern of pod growth. The pod matures after some 10
months. The green pods are much heavier than the ripe ones, containing about 70%
water whereas pod water content at maturity is about 12-18%.
Promoting the conservation and use of underutilized and neglected crops. 17. 19
Fig. 6. Stages of carob pod development (from Ilahi and Vardar 1976, reprinted with permission).
2 0 Carob tree.
5 Origin and centres of diversity
The centre of origin of C. siliqua is not clear. It was placed by De Candolle (1883)
and Vavilov (1951) in the eastern Mediterranean region (Turkey and Syria).
However, Schweinfurth (1894) regarded carob as native to the highlands of
southern Arabia (Yemen). More recently it has been considered by Zohary (1973)
as originating from a xerotropical Indo-Malesian flora, grouping it with Olea,
Laurus, Myrtus, Chamaerops and others and placing the origin of its genus also on the
Arabian peninsula. Ceratonia oreothauma, the only known carob-related species, is
considered to have its centre of origin in southeast Arabia (Oman) and around the
African horn (north of Somalia) (Hillcoat et al. 1980).
Climatically the centres of origin of the subfamily Caesalpinoideae were warm
and moist initially, but after the Cretaceous period vast drying and elevation of the
lands occurred so that cooler, much drier, even desert, conditions evolved. Other
caesalpinioid legumes are mainly tropical and subtropical (Cowan 1981). In
addition, Mitrakos (1988) suggested that the carob tree seems to have evolved
under a climate other than Mediterranean.
The original distribution of C. siliqua is not clear as it has undergone extensive
cultivation since ancient times. Hillcoat et al. (1980) suggested its range in the wild
included Turkey, Cyprus, Syria, Lebanon, Israel, southern Jordan, Egypt, Arabia,
Tunisia and Libya and that it moved westward at an early stage. Carob is believed
to have been spread by the Greeks to Greece and Italy and then by the Arabs along
the coast of northern Africa into the south and east of Spain, from where it migrated
to the south of Portugal and the southeast of France. Its wild occurrence in the
western Mediterranean is doubtful according to Zohary (1973). Spontaneous
carobs occur in many places around the western Mediterranean basin but they are
regarded as feral derivatives of the fruit crop which probably evolved under
As a food source, carob pods could be stored and transported long distances.
In most of the Mediterranean region wild and naturalized carobs are distributed
in more or less the same geographic and climatic belt as the cultivated. Forms of
spontaneous carobs are particularly common at low altitudes along the Spanish
Mediterranean coast, southwest Spain, southern Portugal, the Balearic Islands,
southeast France, the shores of southern Italy including Sicily, the Adriatic coast of
Croatia, the Aegean region in Greece and Turkey, along the northern and southern
ranges of the isle of Cyprus, in the islands of Malta, in the maritime belt of Lebanon
and Israel, the north and south of Morocco and the coastline in Tunisia. The
proposed centre of origin and world distribution of carob are presented in Figure
The carob tree was likely introduced into the United States from Spain by the US
Patent Office in 1854. In the 1950s W. Rittenhouse and J.E. Coit promoted this species
Promoting the conservation and use of underutilized and neglected crops. 17. 21
in California and introduced budwood of selected cultivars from Cyprus, Israel,
Tunisia, Greece, Yugoslavia, Crete, Portugal, Italy and Spain. Seedling trees grown for
shade on the streets of cities in southern California and Arizona were selected for
commercial production on the basis of their floral and fruit characteristics (Condit
1919; Coit 1949, 1967; Schroeder 1952; Coit and Rittenhouse 1970; Brooks and Olmo
In Mediterranean countries, the distribution of the evergreen sclerophyllous
species like C. siliqua is controlled by winter cold stress (Mitrakos 1981). The closely
related species C. oreothauma seems to be even more cold sensitive (J.H. Brito de
Carvalho, pers. comm.) and thus its limits are more restricted. Carob is one of the
most characteristic and dominant trees in the lower zone (0-500 m and rarely up to
900 m asl) of the Mediterranean evergreen maquis (Zohary and Orshan 1959; Folch
i Guillen 1981). In some areas along the shores of the Mediterranean sea, wild
carobs occupy places not disturbed by cultivation. Distribution of C. oreothauma is
restricted to Oman and Somalia, which might be due to it being an uncultivated
species. It is not clear if the distribution of the two related species overlaps. Both
species, apart from probable dispersal by animals, are dependent on dispersion by
Scant information is available on the origin and domestication of the carob tree.
Liphschitz (1987) reported that early archaeobotanical findings (charred wood and
seeds) in Israel showed that the carob existed in the eastern Mediterranean long
Fig. 7. World carob distribution and centres of origin.
2 2 Carob tree.
before the start of Neolithic agriculture (4000 BC), although it is not among the
prehistoric species listed by Renfrew (1973). Zohary (1973) suggested that the
Mediterranean region has been at least one of its domestication centres. Zohary
(1996), on the basis of literature sources and archeological evidence, reported that
the carob was brought into cultivation relatively late with the ‘second wave’ of fruit
crops domesticated in the Old World. He attributed this lateness of domestication
to the difficulty of propagating carob vegetatively. Remains of carbonized pods
have been found in archeological excavations near the Vesuvio volcano in
Campania, Italy, post-dating its eruption in AD 79 (Meyer 1980).
Zohary and Spiegel-Roy (1975) analyzed two kinds of information – evaluation
of fossil evidence and examination of wild relatives of the cultivated crops – and
concluded that olive, grapevine, date palm and fig were the first important
horticultural crops added to the Mediterranean grain agriculture. These ‘first
wave’ fruit trees were most likely domesticated in the Near East in prehistoric
times (4th and 3rd millenia BC); they were very important crops in the Early Bronze
Zohary (1996) suggested that similarly to most Old World fruit crops,
domestication of C. siliqua was based on shifting from sexual reproduction (in the
wild) to vegetative propagation (under cultivation). In carob, as in other fruit and
nut trees, the shift to vegetative propagation is the cultivator’s solution to the
problem of wide variability which is characteristic of sexual reproduction in cross-
pollinated plants. In addition, as a predominantly dioecious tree, carob includes
about 50% males and 1% hermaphrodites (Condit 1919). Thus spontaneous
promising seedlings showing superior features have been empirically selected by
growers and then clonally propagated. As a consequence, wild carob trees
currently growing in Mediterranean countries are not identical to the species type
(Mitrakos 1988). Hillcoat et al. (1980) reported that its cultivation in ancient times
would have been unnecessary since wild trees were common in the eastern
Wild and escaped carobs reproduce by seed while cultivated varieties are
propagated vegetatively as clones. The carob does not root easily by cuttings and
is only easily multiplied by budding. The propagation predominantly of female
clones can change the sex ratio in a carob-production area. The three main fruit
traits that distinguish domesticated carobs from their wild relatives are larger bean
size, more pulp and greater sugar content. Increase in the size and number of seeds
is less evident. These pod features together with productivity and environmental
adaptation seem to have been the most important selection criteria for growers.
The small difference in size between the pollen of the two species of this genus
seems unlikely to be associated with polyploidy but is more likely to be a result of
cultivation (Ferguson 1980; Graham and Barker 1981). Ferguson (1980) reported
that similar differences in pollen size between specimens of Olea europaea (cultivated
olive) and Olea laperrinei (wild olive) have been observed.
Promoting the conservation and use of underutilized and neglected crops. 17. 23
The two main carob pod constituents are (by weight): pulp (90%) and seed (10%).
Chemical composition of the pulp depends on cultivar, origin and harvesting time
(Orphanos and Papaconstantinou 1969; Davies et al. 1971; Vardar et al. 1972; Calixto
and Cañellas 1982; Albanell et al. 1991). Carob pulp is high (48-56%) in total sugar
content (mainly sucrose, glucose, fructose and maltose) (Table 1). In addition it
contains about 18% cellulose and hemicellulose. The mineral composition (in mg/
100 g of pulp) is: K=1100, Ca=307, Mg=42, Na=13, Cu=0.23, Fe=104, Mn=0.4, Zn=0.59
according to Puhan and Wielinga (1996). Rendina et al. (1969) found the lipids to
consist of approximately equal proportions of saturated and unsaturated acids.
Vardar et al. (1972) found five amino acids in pod extracts (alanine, glycine, leucine,
proline and valine) and Charalambous and Papaconstantinou (1966) also reported
tyrosine and phenylalanine.
Table 1. Average composition of the carob pulp
Total sugars 48-56
Condensed tannins 18-20
Non-starch polysaccharides 18
Source: Puhan and Wielinga (1996).
Ripe carob pods contain a large amount of condensed tannins (16-20% of dry
weight) (Würsch et al. 1984). Feeding trials showed that carob pulp contains only
1-2% digestible protein and is relatively low in metabolizable energy (Vohra and
Kratzer 1964). In food value, carob pods are similar to most cereal grains (NAS
1979). The protein has a low digestibility because it is bound with tannins and fibre
(Loo 1969). Some researchers have suggested that condensed tannins account for
observed growth-depressing effects on animals fed with a diet high in carob meal
(Kamarinou et al. 1979) while others believe that this effect is due to its low energy
content for which animals can compensate by increasing consumption (Louca and
2 4 Carob tree.
Constituents of the seed are (by weight): coat (30-33%), endosperm (42-46%)
and embryo or germ (23-25%) (Neukom 1988). The seed coat contains antioxidants
(Batista et al. 1996). The endosperm is the galactomannan carob bean gum (CBG).
It is a polysaccharide molecule composed of mannose and galactose sugar units
(ratio 4:1) rather similar to guar gum (ratio 2:1) and tara gum (ratio 3:1) (Fig. 8).
The main property of this natural polysaccharide is the high viscosity of the
solution in water, over a wide range of temperature and pH (García-Ochoa and
Casas 1992). Two other important properties of CBG are its high water-binding
capacity to form very viscous stable solutions in high dilution (1% and lower) and
its potential interaction with other polysaccharides, having a synergistic effect
(Puhan and Weilinga 1996). Functional properties of CBG are given in Table 2. The
germ meal, which is obtained from the cotyledons and has a 50% protein content,
is suitable for human and animal nutrition (Table 3).
Table 2. Functional properties of carob bean gum (CBG)
Fig. 8. Molecular structure of three galactomannans (from Puhan and Wielinga 1996, reprinted
Promoting the conservation and use of underutilized and neglected crops. 17. 25
Function Example Use level (%)†
Adhesion Glaces, juices 0.2–0.5
Binding agent Pet foods 0.2–0.5
Body agent Dietetic beverages 0.2–1.0‡
Crystallization inhibitor Ice cream, frozen foods, bread 0.1–0.5
Clouding agent Fruit drinks, beverages <0.1
Dietary fibre Cereals, bread 0.2–0.5
Foam stabilizer Whipped topping, ice cream 0.1–0.5
Gelling agent Pudding, desserts, confectionery 0.2–1.0
Moulding Gum drops, jelly candies 0.5–2.0
Protective colloid Flavour emulsions 0.2–0.5
Sterilizing agent Salad dressings, ice cream 0.1–0.5
Suspending agent Chocolate milk <0.1
Swelling agent Processed meat products 0.2–0.5
Synergistic agent Soft cheeses, frozen foods 0.2–0.5
Thickening agent Jams, pie fillings, sauces, baby food 0.2–0.5
† As such or as component in an appropriate blend.
‡ Depending on degree of polymerization or viscosity of CBG.
Source: Puhan and Wielinga (1996).
Table 3. Average composition of commercial carob germ meal
Lipids (neutral) 8
Crude protein (N x 6.25) 52
Carbohydrate (by difference) 27
Source: Puhan and Wielinga (1996).
2 6 Carob tree.
The carob is one of the most useful native Mediterranean trees. In producing
countries, carob pods have traditionally been used as animal and human food and
currently the main use is the seed for gum extraction. Carob pods provide fodder
for ruminants (Louca and Papas 1973) and nonruminants (Sahle et al. 1992). In the
wild, carob shelter, foliage and beans attract browsing animals. The pods contain
indigestible and valuable seeds. Carob timber is hard and close-grained, and has
been used to make utensils as well as fuel. Carob wood also was traditionally used
to make slow-burning charcoal. Ceratonia oreothauma is extensively used for goat
fodder in its native ranges (Hillcoat et al. 1980).
The pods are used after crushing to separate seed and pulp. The main products
derived from the carob pod and some uses are presented in Table 4.
Table 4. Main products derived from the carob pod (pulp and seed) and some major
Product Processing Uses
Kibbles Any Animal feed (horses and ruminants)
Milled Human food and animal feed
(ruminants and nonruminants)
Extraction and purification Sugar and molasses
Fermentation and distillation Alcohol and microbial protein
Extraction Tannins as antidiarrhoea
Powder Washing, drying, roasting Food ingredient; cacao substitute;
and milling preparation of dietary and
Endosperm Grinding CBG or E-410; food additive
(stabilizer and thickener); dietary
fibre; pet food; pharmaceuticals;
Embryo Grinding Germ meal; human and animal
Coat Extraction Tannins for leather tanning
Source: Batlle (1997).
The pulp can be ground into a fine powder for use in human nutrition. Carob
powder consists of 46% sugar, 7% protein and small amounts of numerous minerals
and vitamins and is thus quite nutritious (Whiteside 1981). After oven-drying, the
Promoting the conservation and use of underutilized and neglected crops. 17. 27
powder can be added to cakes, bread, sweets, ice creams or drinks as a flavouring
(NAS 1979; Vidal 1985; Fig. 9a). Carob powder ‘cocoa’ has advantages over
chocolate in that has fewer calories and neither caffeine nor theobromine
(Whiteside 1981; Craig and Nguyen 1984). Its flavour is not as rich as dark chocolate
but resembles milk chocolate.
Owing to the high sugar content of the pod and its relatively low cost, carob
pulp was among the first horticultural crops used for the production of industrial
alcohol by fermentation in several Mediterranean countries (Merwin 1981). In
some countries, e.g. Egypt, carob syrup is a popular drink obtained by extracting
carob kibbles with water. Single-cell organisms have been used to convert carob
pulp into a high-protein feed; sugar solutions extracted from carob pods are an
Fig. 9. Carob products for
confectionery (a), and carob
trees used as ornamentals
in Los Angeles, California
2 8 Carob tree.
excellent substrate for culturing fungi such as Aspergillus niger and Fusarium
moniliforme and the dried mycelium is a palatable and nutritious feed containing up
to 38% crude protein by weight (Imrie 1973; Sekeri-Pataryas et al. 1973).
Milled and chopped carob pomace, which are two by-products of the carob
molasses industry, were tested in Lebanon as a potting medium for plants and have
shown good promise as substitutes for peat-based mixtures in nurseries (Rishani
and Rice 1988). The possible use by the food industry of natural antioxidants
contained on the carob seed coat as a by-product of the CBG industry recently has
raised some interest (Batista et al. 1996).
The carob product most widely used, especially for the food industry, is the
carob bean gum (CBG), or locust bean gum (LBG). This gum comes from the
endosperm of the seed and chemically is a polysaccharide, a galactomannan. By
weight, about a third of the seed consists of gum and it is obtained from the kernel
after removal of the coat and grinding. One hundred kg of seeds yields an average
of 20 kg of pure dry gum (Jones 1953). Carob gum is produced in various degrees
of purity depending on how well the endosperm is separated from the embryo and
seed coat. Specks of cotyledons and testa are usually present in commercial CBG
preparations. For use as a natural food additive, known as E 410, only high grade
is admitted; for pet food more residues are allowed.
This mucilaginous gum, also known as ‘tragasol’, is used in a wide range of
commercial products as a thickener, stabilizer, binder and gelling or dispersing
agent. The food industry uses CBG for the production of a large number of
different commodities: ice creams, soups, sauces, cheese, fruit pies, canned meats,
confectionery, bakery products and pet foods. Technical applications of CBG
include cosmetics, pharmaceuticals, film emulsions, paints, polishes, ceramics and
adhesives (Salari 1982; Johnsen et al. 1988; Neukom 1988; Tous and Batlle 1990) and
are summarized in Table 5. In the 1980s, CBG applications were: food industry
(about 75%) and technical (about 25%); however, this has changed in the 1990s
(because of a CBG price increase) to about 90 and 10%, respectively (Batlle 1997).
Consumption of hydrocolloids in some European countries and the USA is
presented on Table 6.
Carob is widely planted as an ornamental and shade tree on the streets of
California, Australia and elsewhere; male trees are preferred as they do not
provide litter from pod fall. However, the carob’s value as a drought-tolerant, air-
pollution tolerant, low-maintenance tree for street and landscape planting could be
limited by the large mature size and strong, invasive roots (Coit 1951; NAS 1979).
Carob is now being used in xerogardening in Mediterranean countries. And since
it requires little if any cultivation, tolerates poor soils and is long-lived, carob tree
is often recommended for reforestation of degraded coastal zones threatened by
soil erosion and desertification. It also has been recommended for planting as a
windbreak around orchards (NAS 1979; Esbenshade and Wilson 1986) and could
even have some use for buffering noise from factories, roads and railways because
of its dense foliage.
Promoting the conservation and use of underutilized and neglected crops. 17. 29
Table 5. Carob bean gum uses and technical applications
Industrial use Applications
Pharmaceuticals Anticoeliac products, pomades, pills, toothpaste
Cosmetics Emulsions and foams, shaving foam
Textiles Colouring thickener
Paper Flotation product for recovering material; thickener
for surface treatment
Chemicals Glues, colouring, polishing, dyeing, matches, pesticides
Petroleum Flocculation additive to increase stability
and thickness of welling
Mining Flotation product
Well sinking Wall reinforcement, moisture absorbent
Concrete To strengthen solidification
Explosives Water binder for explosives
Source: Adapted from Droste (1993).
Table 6. Hydrocolloids consumed (grams per person per year) as food additives in
Hydrocolloids USA D, F, I and UK†
Starch products 1300 1281
Gelatine 65 122
Agar-agar 2 3
Alginates 10 10
Carrageenans 11 18
Guar gum 34 39
Arabic gum 22 59
Carob bean gum (CBG) 8 18
Carboxy methyl cellulose (CMC) 23 6
Other cellulose derivatives 6 1
Xanthan gum 13 3
Pectin 11 19
Total 1505 1579
† D=Germany, F=France, I=Italy, UK=United Kingdom, and USA=United States of America.
Source: Puhan and Wielinga (1996).
3 0 Carob tree.
8 Genetic resources
8.1. Existing genetic variation
Wild carob trees are still frequently found in the most eastern Mediterranean
regions and are naturalized in the west. Throughout the Mediterranean region
wild or naturalized carob trees in situ were often used as stocks for budding with
selected cultivars. In some areas, such as in Mediterranean Turkey or in the south
of Spain and countries like Morocco, pods from ungrafted spontaneous trees are
collected (Vardar et al. 1980; Ouchkif 1988; Batlle and Tous 1994).
Since antiquity, the cultivated carob has been propagated, first by seeds and
later by budding too. Thus, carob cultivars originated from chance seedlings
selected from local populations and later established in commercial orchards.
Zohary (1973) pointed out that the cultivated carob has not diverged much from its
wild ancestor. This may be true in some areas but certainly not in all as large
morphologic differences in trees and fruit are observed. Carob seedling ‘escapes’
from plantations into the surrounding countryside are frequently observed.
Centuries of cultivation have resulted in a number of local cultivars differing in
habit, vigour, size and quality of pods, seed yield, productivity, and pest and
disease resistance. Most cultivars are of unknown origin and represent the
germplasm of each region. In the world, fewer than 50 named cultivars of limited
distribution are reported in the literature (Tous and Batlle 1990). Carob cultivars
show high genetic variation in morphologic, agronomic and technologic characters.
However, isoenzyme and DNA analyses have revealed low polymorphism
between cultivars of different (Tous et al. 1992; Batlle et al. 1996) and the same origin
(Barracosa et al. 1996). In addition, cultivated and naturalized carobs were
isoenzymically similar (Batlle et al. 1996). This was unexpected as this species is
more or less an obligate outcrosser. However, this lack of diversity suggests the
narrow origin of the cultivated carob. Thus genetic drift and selection pressure
which produce genetic erosion may have represented important drawbacks for the
conservation of the genetic variability of this species. Isoenzymic differences in sex
(female or hermaphrodite) or patterns of geographical variation were not observed
(Tous et al. 1992; Batlle et al. 1996).
Female plants always have been selected in preference to the hermaphrodite
ones, as they are better pod bearers. The most common cultivars in commercial
orchards are female, only a few hermaphrodites having sufficiently desirable
attributes. Hermaphrodites are never the main producing trees in orchards, and
often, male pollinators are isolated seedling trees or branches left on the rootstocks
after budding female cultivars. However, hermaphrodites are of interest as
pollinators; some Italian types like ‘Bonifacio’ and ‘Tantillo’ were selected for this
purpose (Russo 1954) and some Spanish types are being evaluated at IRTA’s
collection (Tous et al. 1996).
The main selection objectives have traditionally been large pod size and high
pulp and sugar content. It is known that pulp and seed content show a negative
Promoting the conservation and use of underutilized and neglected crops. 17. 31
correlation. Thus growers have been selecting against seed yield which is currently
more valuable commercially. For this reason some collecting from wild
(naturalized) populations has been carried out in Andalusia, Spain (Batlle and Tous
1994; Tous et al. 1995) and should be undertaken in countries like Morocco and
The most interesting features of the domesticated carob genetic resources are:
• low number (less than 50) and antiquity of named cultivars
• limited diffusion of cultivars, mainly local
• high genetic variation for some traits:
- morphological (size, shape and colour of the pod, seed yield, etc.)
-agronomical (vigour, habit, resistance to pest and diseases, productivity,
- technological (flavour and sugar content, quality and gum content, etc.)
• low polymorphism for molecular markers (isoenzymes and DNA).
The main cultivars grown in Spain and in other countries are listed in Tables 7
and 8, respectively.
Table 7. Main carob cultivars grown in Spain
Cultivar Growing areas t %
‘Negra’ Tarragona, Castellón, Barcelona 24.726 18.31
‘Matalafera’ Valencia, Alicante 13.110 9.70
‘Duraió’ Majorca, Ibiza 9.062 6.71
‘Rojal’ Tarragona 5.820 4.31
‘Bugadera’ Majorca 4.600 3.40
‘Costella d’Ase’ Majorca 3.750 2.80
‘Mollar’ Murcia 3.200 2.40
‘Lindar’ Alicante 2.072 1.53
‘Melera’ Valencia, Alicante 2.053 1.50
‘Sayalonga’ Málaga 1.650 1.20
‘Comuna’ Alicante 1.647 1.20
‘Boval’ Ibiza 1.250 0.92
‘Del Pom’ Castellón 0.988 0.73
‘Banyeta’ Castellón 0.710 0.52
‘Borrera’ Alicante 0.693 0.51
‘Cacha’ Valencia 0.490 0.40
‘Banya de Cabra’ Barcelona 0.400 0.30
‘Casuda’ Castellón, Alicante 0.354 0.26
Other cultivars 58.425 43.30
Total 135.000 100.0
Source: modified from Tous
3 2 Carob tree.
Table 8. Main carob cultivars grown in countries other than Spain
Country Region or district Cultivar or type
Italy Sicily ‘Gibiliana’, ‘Racemosa’, ‘Saccarata’
Apulia ‘Amele di Bari’
Portugal Algarve, Alentejo ‘Mulata’, ‘Galhosa’, ‘Canela’, ‘AIDA’
Morocco Fes, Marrakech, Agadir ungrafted wild trees
Greece Crete ‘Hemere’, ‘Tylliria’
Cyprus All islands ‘Tylliria’
Turkish area ‘Koundourka’, ‘Koumbouta’
Turkey Mediterranean coast ‘Wild’ and ‘Fleshy’ types
Izmir ‘Sisam’ type
Israel ‘Tylliria’, ‘Sandalawi’, ‘Habati’,
USA California ‘Santa Fe’, ‘Clifford’, ‘Bolser’, ‘Grantham’
Australia South Australia ‘Bath’, ‘Irlam’,’ Maitllan’
Western Australia ‘KP-1’,’ Princess’, ‘Marshall no. 1’
Source: Tous e
Spanish cultivars are largely characterized by high pulp content and medium
seed yield (8-10%). Some cultivars from the Balearic Islands give a high seed yield
(16%) and spontaneous ecotypes from Andalusia even higher but the main cultivar
‘Negra’ yields only around 8%. Italian cultivars tend to have medium pulp and seed
content. Most Portuguese cultivars produce medium to high (10-12%) seed yield
and beans with round kernels well suited for gum extraction. In Cyprus, carob
trees constitute a remarkably uniform group for some features but produce low to
high seed content (8-15%) having relatively flat seeds, such as ‘Tylliria’ which is
widely grown (Orphanos and Papaconstantinou 1969). In Turkey, where carob
distribution is restricted to the coastal of the Aegean and the Mediterranean, three
types of pods can be found (wild, fleshy and ‘sisam’ or intermediate) (Seçmen 1976).
Turkish production is 70% wild type and the rest fleshy and ‘sisam’, which are
considered as grafted (Vardar et al. 1980). In Crete, where Greek production is
concentrated and carob trees grow wild and cultivated, there is a wide range of
seed yield in cultivars. However, most bean production (around 80%) comes from
‘Hemere’ which gives a seed yield of 9% (Kalaitzakis et al. 1988). Spontaneous
populations from Morocco produce high seed yielding (15%) pods with round
kernels and scanty flesh (Ouchkif 1988). In Tunisia most trees are wild (Crossa-
Raynaud 1960) so presumably seed yield would be high. The description of 27
cultivars is presented in Appendix I.
Promoting the conservation and use of underutilized and neglected crops. 17. 33
Information on the morphologic, agronomic and technologic characteristics of
carob cultivars is scanty. Most are female and originated at least 100 years ago,
presumably as seedling selections. Some work has been done on cultivar
description and characterization (Da Matta 1952; Russo 1954; Goor et al. 1958; Coit
1967; Orphanos and Papaconstantinou 1969; Seçmen 1976; Vardar et al. 1980;
Carlson 1986; Batlle 1985; Tous 1985; Spina 1986; Crescimanno et al. 1988; Marakis
et al. 1988; Batlle and Tous 1990; Tous and Batlle 1990).
Carob cultivars vary widely in a number of characteristics which are of
commercial importance to growers. Some important agronomic and commercial
characteristics of the main carob cultivars are presented in Table 9.
To assess and select cultivars for commercial production in Mediterranean
countries the following traits should be considered (Tous et al. 1996).
On the basis of the flower structure male, female and hermaphrodite cultivars could
be recognized. The female cultivars are the most important trees in commercial
groves of Mediterranean countries. Males and hermaphrodites are normally used
as pollinators. There is no agreement between the different authors on the best
density of pollinators for commercial orchards. However, there is sufficient
information to recommend around 12% (1:8) of pollinators distributed regularly
(as in Fig. 7) (Tous and Batlle 1990). Hermaphrodites have a special value provided
that they are self-fertile and/or cross-compatible, so that no space in the orchard
needs to be wasted for unproductive male trees.
Resistance to environmental stress
Carob trees grow best in calcareous soils, preferably near the sea. They are drought
resistant but tolerate only light frost. Sensitivity to frost is a serious problem in this
crop. The extent of frost damage depends on the temperature within the orchard
and the physiological state of the trees. As several spells of frost have occurred in
various places since records began, some cultivar differences have been observed.
The Portuguese cultivar ‘Galhosa’ seems to be more cold tolerant than ‘Mulata’
(Brito de Carvalho 1988a). In Andalusia ungrafted local types known as ‘Bravia’
seem more tolerant than the grafted cultivars (Tous et al. 1995). Susceptibility to
wind is revealed by broken branches after storms. It is related to wood health, tree
shape and size and thus to cultivar and management.
Production (precocity, yield and alternate bearing)
High yield is an important characteristic for farmers, but regular bearing also has
to be considered as most cultivars show alternate bearing, such as ‘Amele di Bari’
in Italy (Crescimanno 1982), ‘Tylliria’ in Israel (Goor et al. 1958) and ‘Cacha’, ‘Negra’
and some hermaphrodite cultivars in Spain (Martorell 1987; Tous and Batlle 1990).
In addition to these genetic traits, other factors affect yield, such as amount of
pollination, cultural practices, environmental conditions (dry or irrigated orchard),
3 4 Carob tree.
Table 9. Agronomic characteristics of main carob cultivars
Cultivar Origin Sex† Growth Precocity Resistance Suscepti- Pod size‡ Pod Pulp Sugar Seed Endosperm
habit to fruit bility to shape§ content¶ content yield content
in pulp (%) (%)†† (%)‡‡
‘Negra’ Spain F open medium high high short S high – 7-9 -
‘Matalafera’ Spain F open medium low low medium-long S medium – 12-14 58.0
‘Duraió’ Spain F weeping early medium medium medium S low-med. – 16-17 58.0
‘Rojal’ Spain F erect very early low low long C medium – 10-11 56.2
‘Sayalonga’ Spain F open early low low long C medium – 13-14 56.0
‘Ramillete’ Spain H weeping very early high medium medium-long C high – 8-10 50.6
‘Banya Cabra’ Spain F open late medium medium long T low – 13-14 54.3
‘Gibiliana’ Italy F open medium high medium medium C high 38-40 8-10 53.1
‘Amele di Bari’ Italy F erect medium low low medium S high 53-54 8 –
‘Mulata’ Portugal F open early low low medium C medium 40-50 12-14 55.8
‘Galhosa’ Portugal F open late medium low short-medium S low – 14-16 58.3
‘Tylliria’ Cyprus F erect medium high medium medium-long C high 51-52 8-11 49.0
‘Koundourka’ Cyprus F weeping – low low short S low 49-50 14-15 58.0
‘Hemere’ Greece – – – – short-medium C high 56-57 – –
‘Sfax’ Tunisia F open early low low long C med.-high 51-52 9 47.2
‘Santa Fe’ California H open very early medium high long C medium 47-48 10-12 –
† F=female; H=hermaphrodite. - ‡ Medium pod length about 15 cm. - § S=straight; C=curved; T=twisted. - ¶ Pulp dry weight. - †† Medium
seed yield=10%. -
‡‡ % of seed dry weight.
Source: modified from Tous
Promoting the conservation and use of underutilized and neglected crops. 17. 35
The trait precocity is highly desirable in carob to reduce the otherwise
unproductive vegetative phase of the first years and to pay off quickly the costs of
establishment. Some cultivars start to bear early, 4 to 5 years after budding (‘Rojal’,
‘Ramillete’, ‘Mulata’, ‘AIDA’, etc.), while others bear some years later (‘Banya de
Cabra’, ‘Cacha’, ‘Sandalawi’, etc.). Regarding the vegetative period of cultivars
held in Spanish carob collections it was observed that the hermaphrodite types
normally bear sooner (2nd to 3rd year after budding) than female cultivars
(Navarro 1992; Tous et al. 1993, 1996). Graça (1996), in trials with ‘Mulata’ in the
Algarve, Portugal, budded the year before planting, obtained significant pod
production (11.2 kg/ha) 5 years after establishment. Most cultivars begin bearing
early when orchard management and rainfall, or supplementary water, are
Fruit quality (pulp and seed)
The quality of beans depends mainly on the seeds and the pulp in which the seeds are
embedded. Seeds are currently the most important part of the pods as they are used to extract
the valuable carob bean gum (CBG). Pulp value depends on its use (livestock feed or human
food industry) and the contents of sugar, fibre, tannins and flavour (Coit 1961). Chemical
composition of carob pods differs widely according to cultivar and climate. Thomson (1971)
found in 40 cultivars the following percentage ranges by weight at 10% moisture: total sugars
(37-62%), crude protein (2.2-6.6%), crude fibre (4.2-9.6%) and ash (1.5-2.4%). Pods also contain
from 0.46 to 1.46% crude fat (Binder et al. 1959) and 2.6-6.7% tannins by dry weight (Louca and
Papas 1973; Marakis et al. 1988).
The pulp is the main constituent of the pod. Pulp content in the pod ranges from
73 to 95% (Caja et al. 1988; Crescimanno et al. 1988; Marakis et al. 1988), with
corresponding seed contents. Seed yield is an important fruit characteristic that
varies with climatic and soil conditions but is also strongly cultivar related (Brito
de Carvalho 1988a). Wild carobs have produced higher seed yield than cultivated
(Marakis et al. 1988; Di Lorenzo 1991; Tous et al. 1995). In Mediterranean cultivars
the variation recorded ranges from 5 to 27% (Caja et al. 1988; Crescimanno et al. 1988;
Marakis et al. 1988). Albanell et al. (1996) observed that number of kernels per pod
is more important than length or weight and in relation to gum content they found
that seeds should be heavy, thick and short.
The content and quality of gum are also important features. They vary with climate,
soil and cultivar (Brito de Carvalho 1988a). Endosperm, from which the gum is derived,
ranges from 42 to 60% in dry weight (Albanell et al. 1988; Crescimanno et al. 1988).
Ungrafted trees seem to produce seeds with more gum content than cultivars (Marakis et
al. 1988). Gum content differs considerably between cultivars. Under the same
environmental conditions cultivars ‘Duraio’, ‘Matalafera’ and ‘Galhosa’ produce more
gum than ‘Rojal’, ‘Melera’ and ‘Negra’ (Tous et al. 1996). There are also cultivar-related
differences in gum quality, especially regarding viscosity grade, gel strength and content
of galactomannans. The current trend is to grow good dual-purpose cultivars (pulp and
kernel), so that high production of carob kernel can be avoided in the future to stabilize the
3 6 Carob tree.
Pulp flavour is also an important consideration for carobs grown for the food
industry. A test on pulp flavour of 31 cultivars, ranging from 37.1 to 51.6% of total
sugar (reported as glucose), indicated that flavour preference is not directly related
to high sugar content. The hermaphrodite cultivar ‘Santa Fe’ was rated highest; it
has a sweet, nutty flavour and high sugar content (47.5%) (Binder et al. 1959).
Carobs of the better cultivars contain 45-55% of total sugar; poor cultivars contain
Ease of harvesting
Harvesting is the major cost in carob production owing to the expensive and scarce
labour in most developed countries. Manual harvesting of the pods represents 30-
35% of the total production cost for an orchard (Orphanos 1980; Tous 1995b). This
cost can be divided between knocking (or shaking) and collecting operations.
Knocking is a traditional operation performed with thin long poles to knock down
ripe pods. Manual or mechanical harvesting by trunk shakers and manpower
shakers is affected by size and growth habit of the trees, pod distribution in the
branches and pod abscission. Collecting operations depend on yield, size and
shape of pod, and orchard density. The main aim for new carob orchard
establishment should be mechanical harvesting. Some agronomical features of the
tree are important to improve mechanical harvesting of carob.
Tree vigour and growth habit
Current cultivars, especially when well-managed in warm coastal climates, can
reach a large size (6 m high) and the fruit-bearing branches usually droop,
obstructing trunk shakers used in mechanical harvesting. Small trees make harvest
easier. In respect of growth habit there are big differences between cultivars (Table
9, Fig. 10). The current need, if shakers are to be used, is to grow trees (orchard
density about 150 trees/ha), which are reduced in size, with upright growth habit
and rigid fruit-bearing branches (Tous et al. 1996).
Fruit ripening and abscission
The physiological ripening of the pods starts in May-June and is a gradual process
closely related to natural fruit drop. These two phenomena can affect harvest
efficiency. Some cultivars are more prone to fruit abscission than others when
knocked or shaken. For example ‘Matalafera’, ‘Rojal’, ‘AA2’ and ‘Banya de Cabra’
are more prone to abscise pods than ‘Negra’, ‘Tylliria’ and ‘Ramillete’. Generally,
hermaphrodite types need greater force for fruit removal than female cultivars (Tous
The main consideration should be to choose cultivars that produce pods which
ripen simultaneously during the period of maximum abscission, to ease collection
from the ground. Early ripening cultivars would avoid not only flower damage
with the sticks but also rainfall which is frequent at harvesting time (September-
October) in Mediterranean countries.
Promoting the conservation and use of underutilized and neglected crops. 17. 37
Fig. 10. Growth habit: upright
– cv. ‘Rojal’ (a), open – cv.
‘Matalafera’ (b), and weeping
– cv. ‘Duraió’ (c).
3 8 Carob tree.
Fruit shape and size
Carob bean size is a highly variable character influenced by many environmental
factors as well as level of pollination and fruit set. Generally, grafted cultivars
produce larger fruits than unselected wild types. This trait eases both manual and
mechanical harvesting. Pod shape is also highly variable (Table 9, Fig. 11). For
easier and cheaper collection, straight fruits are preferred to curved or twisted
pods (Brito de Carvalho 1988a). The easiest pods to collect are large and straight.
Carob pod size is also important for resistance to strong winds in spring to prevent
premature fruit drop.
The most promising female cultivars studied at IRTA are: ‘Rojal’, ‘Duraió’,
‘Mulata’, ‘AIDA’ and ‘Sayalonga’. Other cultivars like ‘Banya de Cabra’,
‘Matalafera’, ‘Galhosa’ and ‘Tylliria’ also show some commercially interesting
characteristics (Tous et al. 1996). As promising hermaphrodite pollinating cultivars,
‘Clifford’, ‘Santa Fe’, ‘Ramillete’ and ‘A-19’ can be considered. Some outstanding
cultivars from different origins like ‘Amele’, ‘Sfax’, ‘Tylliria’, ‘Casuda’, ‘Santa Fe’
and ‘Clifford’ perform well in many countries. This shows that carob cultivars are
able to adapt outside their region of origin.
The main aim is conservation of variability through a wide range of different
genotypes and, less so, individual genotype preservation. Currently, there are
eight field carob collections in the world (Table 10, Appendix II). The best
documented is maintained at IRTA-Mas Bové, Spain and is supported by the
Spanish Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria
(INIA). This Germplasm Bank comprises field collections placed in two sites, Reus
and Tortosa (80 km away), with two types of Mediterranean climate (Tortosa is
warmer than Reus). Altogether 93 cultivars and selections from eight origins are
held for evaluation. There is some duplication to safeguard against frost damage.
Fig. 11. Variation in pod
morphology of carob types
from Greece (a) and
Andalusia, Spain (b); and of
cultivars: ‘Negra’ – Spain (c),
‘Matalafera’ – Spain (d),
‘Mulata’ – Portugal (e), ‘Rojal’
– Spain (f), ‘Ramillete’
(hermaphrodite) – Spain (g),
‘Banya de Cabra’ – Spain (h),
and ‘Banya de Marrà’ – Spain
Promoting the conservation and use of underutilized and neglected crops. 17. 39
4 0 Carob tree.
Table 10. World carob germplasm collections
Country Place, district† Area Planting Accessions Evaluation
(ha) year native foreign
Spain Reus, Tarragona 1 1987 52 16 Phenological, agronomic,
Tortosa, Tarragona 0.8 1989 59 12 Yield
Palma, Majorca 0.5 1990 39 1 Phenological
fruit quality and yield
Villajoyosa, Alicante 1.5 1986 133 2 Agronomic characteristics
Portugal Tavira, Algarve 0.5 1988 11 2 Pomological characteristics
Tunisia Ariana 1950 10 – None
USA San Diego, California 1960 2 3 None
Australia Loxton, S. Australia 0.3 1985 – 10 Yield
† For full addresses see Appendix II.
Source: modified from Tous
Once the field collections were established and accessions identified, the main
aim has been to characterize the material and assess the genetic variability of
important characters, particularly morphologic, agronomic (precocity, growth
habit, production, pest and disease resistance, etc.) or commercial (kernel yield,
pulp and gum quality, etc.). Such studies could be extended by trials with selected
cultivars. However, this approach has hardly been used for carob and only a few
trials are known.
After recording passport data for each new accession, identification and
characterization are carried out according to an adapted version of the descriptor
list developed by the authors and completed with isoenzyme records (Tous et al.
1992; Batlle et al. 1996). So far, in the 1995-96 cropping year 15 cultivars have started
bearing at Reus and 6 at Tortosa. The preliminary results (8th year after budding)
indicate that the female cultivars ‘Rojal’, ‘Banya de Cabra’ and ‘Ralladora’ and
hermaphrodite accessions ‘Misto Sta. Bárbara’, ‘Ramillete’ and ‘A-19’ are
promising (Tous et al. 1996). Several very promising cultivars have yet to be fully
assessed. Passport data of all introduced cultivars are available as well as some
Apart from the main Germplasm Bank at IRTA, Spain has two other carob
collections. They were started after surveying and cataloguing carob genetic
resources in Castellón, Valencia and Alicante (Navarro 1992) and the Balearic
Promoting the conservation and use of underutilized and neglected crops. 17. 41
Islands (Tous et al. 1996). The Valencian collection is located in Villajoyosa, Alicante
and holds 135 accessions and the other is in Palma, Majorca with 40 accessions. The
Villajoyosa collection, which holds an important number of hermaphrodite types,
is at risk of being lost as it is placed on private land and accessions are not freely
available. Records of these two collections are scarce and generally limited to their
The carob field collection of the Associaçao Interprofissional para o
Desenvolvimento da Produçao e Valorizaçao da Alfarrova (AIDA) in Tavira,
Portugal contains 13 cultivars, documented with passport and evaluation data. For
the other three living collections, it should be noted that only very limited
information is available. In the Tunisian collection at INRAT Ariana, Crossa-
Raynaud (1960) reported that at least one tree of the local cutivar ‘Sfax’ was still
available. The Californian collection is kept in a public garden at San Diego. In
addition, carob as a species is represented in most botanical gardens of the
A carob germplasm collection of some 60 clones was assembled by J.E. Coit in
1949 near Vista, California, holding both North American selections and
Mediterranean cultivars, but it was lost in the 1970s owing to housing development
(Coit and Rittenhouse 1970). In Cyprus, in the 1950s a large cultivar collection was
established at Xylotimbou with the purpose of cultivar characterization (Ticho
1958). However this early collection was also lost some decades later (P.I.
Orphanos, pers. comm.). These two genebanks were the first recorded attempts
to maintain and characterize carob genetic resources in the world and presumably
some accessions were lost after their removal.
Duplications of cultivars exist in field collections but not of wild material. Each
country should concentrate on the conservation of its native resources.
Information on gaps in the existing germplasm collections is largely unknown.
However the expected genetic variation contained in heterogeneous species has
not been found within the cultivated material in some ex situ collections (Tous et al.
1992; Batlle et al. 1996). As most of the remaining carob natural populations contain
high seed yielding genotypes, initiatives should be taken to conserve this
potentially interesting wild material. Among the gaps, the lack of any wild material
from Morocco and Turkey is probably the most important. The existing naturalized
populations of the south of Spain were surveyed and genotypes collected recently
(Batlle and Tous 1994; Tous et al. 1995). Hermaphrodite genotypes are of particular
interest for collection.
The threat of genetic erosion on carob seems moderate. However in some
places like Murcia in the southeast of Spain, Rodriguez and Frutos (1988) reported
37% of trees lost, mainly due to replacement of carob by more intensive crops in
newly irrigated areas. Vinterhalter et al. (1992) used tissue culture in an attempt to
propagate genotypes which were almost extinct in Croatia. In vitro
micropropagation, as a way of conserving outstanding trees, has been developed
by Sebastian and McComb (1986) in Australia and by Alorda and Medrano (1996)
4 2 Carob tree.
in Spain. Androulakis (1994) attempted to propagate selected types by in vitro
culture in Crete. Only limited success has been achieved using these methods.
The wild species C. oreothauma (with its two subspecies) is not represented in
the existing field collections. It is only conserved ex situ as a few potted trees in a
greenhouse at The Royal Botanical Gardens Kew, in London, England. It was
botanically studied by Hillcoat et al. (1980) in its native ranges. In 1991 a collecting
expedition in the mountains of northern Oman was carried out by IBPGR in
collaboration with the Ministry of Agriculture, Fisheries and Food of that country;
6 accessions were collected (IBPGR 1992).
Promoting the conservation and use of underutilized and neglected crops. 17. 43
9 Genetic improvement
To date, improvement of carob cultivars has been carried out only empirically by
growers selecting promising chance seedlings and budding them onto less fruitful
genotypes as rootstocks. The lack of any planned carob breeding programmes may
be due to its relatively minor importance. Breeding programmes mean
considerable costs associated with raising and selecting progenies, and as more
than 8 years may elapse from seed to flower, progress can only be slow. In due
course the use of molecular markers, particularly for sex, could speed early
selection and thus the process. However, the breeding system including pollination
mechanisms and expression of sexuality in response to environmental conditions
is not well understood.
Clonal variability in old carob cultivars could be exploited by selecting the best
clones which have accumulated different spontaneous mutations over a long period
of time. Clonal selection is a valuable approach when used for a cultivar which has
achieved commercial success. In Spain, some work is underway with ‘Rojal’. It
might also be interesting to make some clonal selection in cultivars like ‘Duraió’ if
morphologic or agronomic variation is observed.
9.1 Breeding objectives
The chosen objectives will depend on the use envisaged for the resulting cultivars.
The main challenges for carob improvement are: to reduce vegetative period (i.e.
increase precocity in bearing) and to increase cold hardiness, and pod and seed
yield. Other features like vigour, productivity, uniform ripening, easy harvesting,
kernel size and shape, content and quality of pulp and gum are also important.
Some differences in cold tolerance appear between carob genotypes (Brito de
Carvalho 1988a; Tous et al. 1995), but as reported in the Genetic Resources section,
there are no records of deliberate collection of types from the colder places. This
variability has not been exploited and may not be enough to select adapted types
for different environments and crossing. Wider adaptation through interspecific
hybridization seems difficult to achieve as hardy carob-related species are
9.2 Breeding methods
Conventional breeding by controlled crosses has not been reported in carob, only
empirical selection by growers looking for productive trees of sweet and fleshy
pods in the wild. Identification and propagation of superior phenotypes in natural
populations of chance seedlings, mainly based on seed yield performance, is an
alternative as in some regions of Morocco and Turkey large wild populations still
As carob is largely a dioecious species, genetic improvement for fruit characters
is hampered by lack of information for the male parent regarding these characters.
However the use of hermaphrodite types to cross together or with female cultivars
seems feasible so that both potential parents could be chosen after fruit assessment.
4 4 Carob tree.
Mass selection after intercrossing the best individuals on the basis of their
phenotypes would be the simplest method. This is based on the relatively high
additive variance affecting the inheritance of most traits in fruit and nut trees
(Bringhurst 1983). No inheritance of a character has been described in carob.
Choice of parents with complementary characters from diverse geographical
regions and available in ex situ collections should be criteria to be considered.
Information on pollen and seed management, hybridization and handling seed
populations has not been reported for carob, and thus should be adapted from
other fruit and nut tree crops. Pollen collection is easy and it seems storable in a
fridge for several months (M. Rovira, pers. comm.). Pollen application with brush
or fingers is feasible, flower insect exclusion is necessary. Seed germination and
tree raising are described in the Agronomy section
Interspecific crosses between C. siliqua and C. oreothauma have not been
reported, but would be worth trying. Both species have the same chromosome
number (2n=24) (Hillcoat et al.1980). However, knowledge about C. oreothauma and
its genetic potential is still very limited. As C. oreothauma is adapted to higher
altitudes (1500-1800 m asl) than carob, Hillcoat et al. (1980) suggested that a cross
between them would produce a more useful forage plant. However, C. oreothauma
may be less hardy than carob (J.H. Brito de Carvalho, pers. comm.) in which case
any hybrids are likely to be hardy. As rooting potential is inherited and, if C.
oreothauma shows higher rooting potential than carob, it would be incorporated
through hybridization, but hybrid seedlings would only be useful if are hardy and
show good adaptation.
Promoting the conservation and use of underutilized and neglected crops. 17. 45
10 Production areas
As indicated earlier carob production has a long tradition, mainly for animal
feeding, in most countries bordering the Mediterranean sea. It is thought the
Greeks and Arabs were responsible for the spread of carob within the
Mediterranean basin from the Near East. More recently, it was introduced in
different periods in some warm semi-arid zones of Australia, California, Arizona,
Chile, Mexico, South Africa, etc. However, commercial carob production is
currently concentrated in the Mediterranean region.
The total carob-production area in the world is around 200 000 ha (Table 11) of
which the southern countries of the European Union (Spain, Italy, Portugal and
Greece) with some 148 000 ha account for 74% of the growing area and about 70%
of the world production (Table 12).
Table 11. Area of carob in producing countries
Country Area (ha) % of total production
Spain 82 000 41.0
Italy 30 000 15.0
Morocco 25 000 12.5
Portugal 21 000 10.5
Greece 15 000 7.5
Cyprus 12 000 6.0
Other† 15 000 7.5
Total 200 000 100
† Algeria, Australia, South Africa, Turkey, USA, etc.
Source: Batlle (1997).
Commercial world production of carob pods is estimated currently around 310
000 t, and it is mainly concentrated in Spain, Italy, Portugal, Morocco, Greece,
Cyprus, Turkey, Algeria and other countries (Table 12). There is some production
in Croatia, Tunisia and Malta and small amounts are also produced in Australia,
California and South Africa. Pod and seed production in different countries are not
parallel because of differences in seed yields of cultivars and wild types.
Carob production in the world has declined dramatically over the past 50 years,
from 650 000 t in 1945 (Orphanos and Papaconstantinou 1969) to 310 000 t today. In
Spain alone, production has fallen by 400 000 t, from 550 000 t in 1930 to 150 000 t
in 1990 (MAPA 1994). The main reasons are low prices coupled with farming
mechanization and coastal planning development. Farmers’ interest in carob in
most Mediterranean countries diminished because of low pod prices and home
consumption, and use of coastal land for roads, housing development and
industrial estates (Batlle 1997).
4 6 Carob tree.
Table 12. World carob pod and seed production
Country Pod production Seed production
t % t %
Spain 135 000 43.5 12000 37.5
Italy 45 000 14.5 4000 12.5
Portugal 30 000 9.7 3600 11.3
Morocco 26 000 8.4 4800 15.0
Greece 20 000 6.5 1800 5.6
Cyprus 17 000 5.5 1700 5.3
Turkey 15 000 4.8 1800 5.6
Algeria 7 000 2.3 800 2.5
Other† 15 000 4.8 1500 4.7
Total 310 000 100 32000 100
† Australia, South Africa, USA, etc.
Source: Authors´ compilation.
In the past, carob expansion in Spain took place in two main phases: first the
agricultural development during the 17th century when marginal lands were
brought into use, and later when vineyards were pulled out because of a phylloxera
outbreak in the 19th century and were replaced by this crop in coastal areas (Tous
and Batlle 1990). The largest growing area (190 000 ha) was reached in the 1930s
(MAPA 1994). Spanish production has halved between 1970 and 1995 (MAPA 1994).
The current Spanish growing area and production (82 100 ha and 135 000 t) is
distributed in five regions: C. Valenciana (54 200 ha and 60 500 t), Catalonia (12 700
ha and 28 000 t), Balearic Islands (12 200 ha and 30 500 t), Andalusia (1000 ha and
11 000 t) and Murcia (2000 ha and 5000 t) (MAPA 1994). There are estimated to be
182 000 isolated trees (not in orchards), some of which are intercropped with other
species such as almonds, olives, figs, grapevines, etc. An important number of
naturalized trees thrive in Andalusia.
Carob production in Italy (45 000 t) is mainly located in the island of Sicily
(provinces of Ragusa, 21 000 t; Siracusa 11 000 t; elsewhere, 5000 t) and the mainland
(Apulia and Campania, 8000 t). Production in Sardinia is negligible. Italian
production has halved between 1955 and 1995. The current tendency is to reduce
the area (Licitra 1996).
The carob-growing region in Portugal is concentrated in the south with some
21 000 ha and 30 000-35 000 t of production, depending on years (Droste 1993). The
Algarve is the main producing region and around 60% of the total surface is located
in four places: Silves (3200 ha), Faro (3000 ha) and Loulé and Tavira with 2500 ha
each. In the Alentejo region there are also some orchards in Mértola (100 ha)
Promoting the conservation and use of underutilized and neglected crops. 17. 47
(Martins-Louçâo and Brito de Carvalho 1989). The Portuguese carob production
has declined over the past 20 years and the area under cultivation has reduced by
at least 25% (Droste 1993).
Carob production in Morocco has increased over the last 15 years and it is
estimated to be about 26 000 t (Batlle 1997). The main spontaneous populations are
concentrated in the regions of Tafechma in the north and Ait Ishaq in the south
(Ouchkif 1988). However, three areas are commercially known: Fes, Marrakech
and Agadir. Acreage of spontaneous carob in Morocco is estimated around at 30
000 ha. Carobs thrive together with a number of other species of the maquis
(Pistacia, Olea, Quercus, etc.). Some new orchards have recently been planted and
Moroccan production is expected to rise moderately in the coming years. Carob
pod production in Tunisia is also from spontaneous trees and was estimated in the
1950s to be about 2800 t (Crossa-Raynaud 1960); however, no records are available
Total Turkish production is about 15 000 t, which is collected from isolated trees
(360 000) as there are no carob orchards. The production is concentrated along the
coast in the Aegean (4%) and Mediterranean (96%) regions from Urla (Izmir) to
Samandag (Hatay) (Vardar et al. 1980). The main producing provinces are Içel,
Antalya, Mugla, Adana, Burdur and Aydin.
In Israel, Goor et al. (1958) reported some 250 000 carob trees scattered in
forests. In the early 1950s about 2000 ha were planted either as groves, on grazing
land, as forests or as roadside trees. Currently some plantings are still productive
but the tonnage seems to be decreasing.
In California during the 1950s there was a well-publicized ‘Carob crusade’
promoting this species as a dryland crop needing little irrigation, and several
plantings were made throughout the south. However, mainly owing to low
productivity of the tree under dryland culture and the high cost of land and
processing, the project failed (Coit and Rittenhouse 1970; Ferguson and Arpaia
In Australia, the crop was introduced around 1850 by Mediterranean
emigrants. However, it was only in the 1980s that interest in carob led to planting
some orchards, mainly in Western and South Australia but also in New South Wales
and Victoria. The Australian carob-growing area is only about 170 ha and there are
also some 30 000 isolated trees. Its production is estimated to be around 750 t per
year (Tous 1995a).
4 8 Carob tree.
The carob is a long-lived evergreen and thermophilous tree thriving in habitats
with mild Mediterranean climates. It grows well in warm temperate and
subtropical areas, and tolerates hot and humid coastal areas. Carob and orange
trees have similar temperature requirements but carob tolerates poorer soils and
needs much less water. The carob tree is more tender than the olive. For resistance
to dry environments it is surpassed only by pistachio (Evreinoff 1955). It is also a
xerophytic species well adaptated to the ecological conditions of the Mediterranean
region, by virtue of its efficient hydric regulation by stomatic adjustment and its
foliar structure and anatomy (Catarino et al. 1981). Leaf wax synthesis increases in
dry conditions reducing cuticular permeability and thus protecting the plant from
excess transpiration (Baker and Procopiu 1980). Carob, together with Pistacia
lentiscus L. and Olea europaea L. var. sylvestris, forms one of the most characteristic
associations of the lowest zone of the Mediterranean vegetation and thus is
considered to be a climax community (Oleo-Ceratonion).
Like other Mediterranean species with long-lived leaves and an extended
flowering period, mechanisms have evolved that optimize water, carbon and
nitrogen use for reproduction (Correia and Martins-Louçâo 1995). Several studies
have shown that carob trees can maintain stomata open and high leaf water content
even under low soil water availability (Nunes et al. 1989). This is allowed by a sharp
reduction of leaf water potential in response to small water losses (Lo Gullo and
The two main growing flushes are in spring and autumn as in most
Mediterranean trees. Vegetative growth slows below 10°C. Thus, it seems that this
species enters some kind of ‘light’ dormancy, at least in most cool latitudes.
However in some very warm places and under favourable conditions, carob grows
without becoming dormant either in winter or summer (Liphschitz and Lev-Yadun
1988). The cambium can be active throughout most of the year (Fahn 1953), or all
year with low rates of activity in January (Arzee et al. 1977). Investigations on the
annual rhythm of cambial activity in Italy by Scaramuzzi et al. (1971) showed that
cambium is active from February to the end of September and inactive during
winter months owing to low temperatures.
The rooting habit of carob is similar to pistachio; its extensive root system
penetrates the soil deeply. Carob develops roots under stressful conditions to
explore deeper soil layers where water may be available (Christodoulakis 1992). It
can thus survive long periods of drought. In addition, Nunes et al. (1989) reported
that carob leaves can maintain turgor under situations of soil drought, using
different strategies according to the season.
Although the carob tree is a legume, like most Caesalpinioideae it does not
nodulate and thus is unable to fix nitrogen (Martins-Louçâo and Rodríguez-
Barrueco 1982; Martins-Louçâo 1985). Arbuscular mycorrhizal (AM) fungi have
been shown to colonize carob roots, but no ectomycorrhizal association was found
(Martins-Louçâo et al. 1996b). The colonization by AM can increase nitrogen uptake
Promoting the conservation and use of underutilized and neglected crops. 17. 49
by the plant. Since carobs often grow on nutrient-deficient soils lacking nitrogen
and phosphorus in particular, AM fungi can improve nutrition.
11.1 Climate requirements
Areas suitable for carob should have a subtropical Mediterranean climate with cool,
not cold, winters, mild to warm springs, and warm to hot dry summers. These
Mediterranean-like areas range from approximately 30° to 45° in northern latitudes
(Mediterranean basin, California and Arizona) and between 30° and 40° in
southern latitudes (Australia, South Africa and Chile).
Adult trees require no winter chilling; they can be damaged when temperatures
fall below -4°C and can only withstand winter temperatures of not lower than -7°C.
However, trees can withstand summer temperatures of 40°C and hot dry winds.
From 5000 to 6000 hours above 9°C are needed for pods to ripen. Strong winds can
break adult tree branches and detach pods. Wind can also damage young trees
(Tous and Batlle 1990). Autumn rains can interfere with pollination and affect fruit
set. High humidity in spring promotes Oidium infection on both leaves and pods.
11.2 Soil requirements
Carob trees can adapt to a wide range of soil types from poor sandy soils and rocky
hillsides to deep soils, but they cannot withstand waterlogging although the root
system is usually deep. In areas with shallow rocky soils, tree size and productivity
are reduced. The best soils are sandy well-drained loams but calcareous soils with
high lime content are also suitable. Carob also appears to tolerate salinity well
(Rebour 1971). Winer (1980) reported tolerance to a soil salt content of up to 3%
11.3 Water requirements
Carob, as a xerophyte, can survive dry climates without irrigation and is well
adapted to dry environments with annual average rainfall between 250 and 500 mm
per year (Tous and Batlle 1990). It has developed some drought-resistance
mechanisms (Nunes et al. 1989; Salleo and Lo Gullo 1989) as mentioned in the
Agronomy section. Although drought resistant, carob trees do not bear
commercial crops unless they receive at least 500-550 mm per year (NAS 1979), but
350 mm of annual rainfall are considered enough for fruit set (Coit 1949; Ticho 1958;
5 0 Carob tree.
Carob rootstocks are raised from open-pollinated seeds and these seedling
rootstocks vary widely in vigour, habit and cold resistance. No rootstock trials
have been carried out and no rootstock selections are available. It is essential that
rootstocks produce a well-developed rooting system. The seedling stocks should
be budded 1 year after germination, in the nursery, or 2 years from germination,
after planting in the orchard. Vegetative propagation by cuttings is not yet
commercially available. Young seedlings are very sensitive to frost damage and
thus in frosty places they should be protected.
The seeds used for sowing should be completely ripe and extracted from pods of
the last harvest. Sowing should be done early in the spring, about March-April.
Before sowing, the light, empty or wormy seed should be removed; this can be
done by soaking in water when most of the faulty seeds float on the surface and
can be easily removed. Although carob seeds have remained viable for as long as
5 years stored dry at low temperatures in sealed containers (Goor and Barney 1968;
Hong et al. 1996) it is advisable to use seeds from the current season. Seeds are
presumably viable after passing through an animal’s digestive tract.
Carob seeds germinate easily, but as the coat is very hard they require
scarification with acid or hot water treatment. Germination can be hastened by
treating them with tap water, boiling water, sulphuric acid (H
) or gibberellic
). Carob seeds do not need to be kept in a cold store to break dormancy.
At IRTA-Mas Bové good results were obtained using fresh seed sown in March-
April, with any of the following methods or combinations of methods:
• soaking in tap water at room temperature for 15 days
• soaking in boiling water, stirring briskly for 10 minutes and then immersion
in cold water for 24 hours
• soaking in concentrated sulphuric acid for 1 hour and then rinsing with tap
water to prevent complete digestion of the seed coat
• soaking in gibberellic acid (25 ppm) for 24 hours.
Frutos (1988) scarified carob seeds with sulphuric acid solutions (10, 20, 30, 40
and 80%) for 30 minutes and then soaked them in water for 24 hours and placed
them in Petri dishes at 23°C; he obtained the best germination (99.1%) using
sulphuric acid at 80%. However, he observed no effects on seed germination after
treatment with GA
at 50, 100, 200 and 400 mg/L for 24 hours. After treatment and
washing, seeds are usually soaked for another 1-2 hours before planting and are
sometimes surface-sterilized with dilute bleach. After soaking, water is drained
away and the seeds are sown either into polyethylene trays on greenhouse benches
and kept at 20-30°C or directly into tall plastic pots (12-15 cm diameter and 35-40
cm deep) placed outside under shading.
Promoting the conservation and use of underutilized and neglected crops. 17. 51
Optimum temperature for carob seed germination was found to be 25°C by De
Michele et al. (1988) and 27.5°C by Mitrakos (1981). However, in its native ranges
when these temperatures prevail (June-September) no water is available. It seems
likely that some germination occurs naturally in November and seedlings survive
when winter is mild (Mitrakos 1988). There is good evidence from Hillcoat et al.
(1980) that the optimum temperature for C. oreothauma seed germination is similar
to that reported for carob. Work on the effect of water stress on germination has
been done by Spyropoulos and Lambiris (1980).
Different potting mixtures can be used. They usually contain soil, humus,
perlite and peat moss in various ratios, and are usually amended with sand to
improve drainage and structure. The germinated seed should be watered
regularly, but not overwatered, as this can result in damping-off and root rot
diseases. The benches on which the trays are placed should be clean and sterile, as
several pathogens can survive on dirty benches and infect young carob rootstock
seedlings. Care should be taken when handling seedlings.
Carob has been described by Lee et al. (1977) and Hartmann and Kester (1983) as
difficult to root. Its adventitious rooting potential is low, but rooting has been
obtained on subterminal hardwood cuttings (2 or 3 years old) (Fig. 12a), after
treatment with sulphuric acid and a high concentration of hormone (IBA or IBA
combined); a rooting bench containing perlite and fitted with bottom heat (24±1°C)
and mist (once every 2 min during the day) was used (Alorda et al. 1987). It appears
that three aspects of the cuttings are important for rooting: time of collecting
(seasonal variation), type of shoot (age and position) and genotype (rooting
potential). Alorda and Medrano (1988) in Majorca, Spain, and Cabrita et al. (1988)
in the Algarve, Portugal, observed the highest rooting percentage in March cuttings
while for Fadl et al. (1979) in Egypt it was in April. Regarding genotype the best
rooting percentages were obtained by Alorda and Medrano (1988) using ‘De la Mel’
(syn. ‘Negrillo’) (85%) and one local hermaphrodite selection (45%) and by Cabrita
et al. (1988) using ‘Galhosa’ (44%) rather than ‘Mulata’ (27%). Alorda and Medrano
(1988) reported success after transplanting to the field with irrigation while Cabrita
et al. (1988) described plant failure after transplanting to a soil mixture under
greenhouse conditions. De Michelle and Occorso (1988) in Sicily obtained the
highest rooting percentage (57.9%) using semihardwood cuttings with leaves taken
in March and treated with IBA (8000 ppm).
Micropropagation of carob using both juvenile and adult tissues has been
attempted (Martins-Louçâo and Rodriguez-Barrueco 1982; Sebastian and McComb
1986; Vinterhalter et al. 1992; Androulakis 1994; Alorda and Medrano 1996).
However, there are no reports of plants from in vitro culture being successfully
established in the field.
It seems that vegetative propagation by cuttings has not yet been successfully resolved
in carob to give consistent results and thus to be suitable for mass production
5 2 Carob tree.
Fig. 12. Hardwood cutting propagation (a), seed propagation (b) and modern orchard, 8 years
old, in Tarragona, Spain (c).
Promoting the conservation and use of underutilized and neglected crops. 17. 53
nurseries. The information available on cutting propagation is more useful now
than 15 years ago. Attempts have been made but it has not yet been solved.
Research is underway at IRTA. If an easy way to root cuttings is developed,
propagation of cultivars would be simpler and much cheaper.
Planting and transplanting of seedling rootstocks
Seedling rootstocks, before or after budding, are usually planted from pots directly
into the orchard. As carob is an evergreen and seedlings are sensitive to frost and
root drying, late transplanting in February or March is recommended after danger
of frost is past; the use of bare-rooted trees is not advisable.
Trees with well-developed roots should be used for transplanting (Fig. 12b)
and proper care during and after planting is essential. Unlike other fruit trees,
carobs are not usually budded in the nursery; field budding 1 year after planting
has proven superior for vigour. The plastic pot is removed by cutting it from the
top to the bottom with a sharp knife. Trees should be well watered immediately
after planting, and soil moisture should extend below the root zone. This also helps
to eliminate air pockets. A second irrigation follows within 2 weeks, followed by
regular fertilization, using mainly nitrogen in the ammonium form rather than
nitrate because of its easier uptake (Cruz et al. 1993). Rootstocks should be staked
on the downwind side to ensure straight tree growth for budding and to protect
them from excessive wind, which is common in coastal areas around the
Mediterranean. It is essential to water 2 or 3 times during the first summer after
planting in the orchard to wet the root mass and adjacent soil for successful
establishment and for growth to reach a good size for budding the following
The potential use of C. oreothauma as rootstock for carob seems not feasible as
it is more tender than the cultivated species (J.H. Brito de Carvalho, pers. comm.).
Scion cultivars are propagated with standard budding techniques. Some research
on this matter has been reported (Brito de Carvalho and Graça 1988; Tous and Batlle
1990). The main types of budding used are T-bud, chip bud and patch bud. Budding
is usually done in spring (from April to early June) when the scion buds are mature
and the bark on the rootstock is slipping and active. When planting a new carob
orchard, rootstocks are planted in late February or March and usually budded the
following year in spring.
T-budding is the most efficient and common method in spring (April-May) with
well-developed buds from scion wood of the year before on rootstocks of 1-2 cm
diameter. Patch budding requires a larger rootstock diameter (bigger than 2 cm)
and is thus more likely to be made in the field in spring or autumn. Bud take in
rootstocks of less than 1 cm of diameter is low. Chip budding could be useful for
these types of plants, but an accurate matching of cambia is required for this
Both T and patch budding are performed when the rootstocks bark is slipping
5 4 Carob tree.
during spring. If bud take is unsuccessful, rootstocks are rebudded in September. For
successful budding a sharp knife should be used to make smooth cuts. Budding wraps can
be made of various materials, but plastic is the most common and widely used.
12.2 Orchard design
Tree densities in carob orchards of Mediterranean countries have traditionally been low and
variable, within the range of 25-45 trees/ha which means square tree spacing from 20 x 20
m to 15 x 15 m. Rectangular planting has also been a common design. Intercropping with
species like olive, grapevines or almond is frequently found. Most of the areas where carob
trees will grow are semi-arid or marginal for good horticultural production. In modern
orchards there is a tendency to reduce spacing with the aim of intensifying the crop. Carobs
are long-lived trees and a well-designed orchard should ensure early economic bearing,
maximum production potential, adequate pollination and sufficient space for
management (Fig. 12c).
A carob orchard reaches its maximum bearing potential when space over the soil is
filled by pod-bearing trees with sufficient light penetration to keep fruiting wood
productive. As the orchard develops, and before maximum bearing potential is reached,
bean yield is directly related to the number of trees per hectare. Currently, for dryland
orchards on poor soils of the Mediterranean coast, tree densities between 100 and 175 trees/
ha are recommended, i.e. spacings from 9 x 9 m to 7 x 8 m (Tous and Batlle 1990).
When carobs are to be planted in fertile soils, high-density planting and tree thinning
later may be considered. Early yield can be maximized by initially planting more trees per
hectare than will be needed for maximum bearing potential. As trees grow,half of them may
be removed, but at considerable expense, to avoid tree crowding. Crowding results in yield
losses from tree competition for light, nutrients and water, excessive pruning costs, and
difficulty in conducting cultural and harvest operations. The closer the plantings, the more
likely thinning will be required. In California, Coit (1951) suggested a spacing of 9 x 4.5 m
and tree removal some 10 years after planting to obtain a spacing of 9 x 9 m. In good soils
of the Algarve, Portugal, an initial density of 6 x 4 m and later thinning to a density of 6 x
8 m was proposed (Brito de Carvalho 1985). When the filler trees should be removed
depends on tree growth. However, most new orchards are being planted at permanent tree
density as tree removal is often not convenient for growers.
Another alternative in young carob orchards is intercropping with early bearing species
such as peach, almond or even vegetables. Planting an annual or perennial crop between
the rows may give early returns to the investment. Care should be taken to choose pesticides
compatible with the nonbearing carobs. In most cases intercropping may a damage carob
orchard and cause problems for the grower.
As described earlier, carob trees are generally dioecious with occasional hermaphrodite types.
Thus female, male and hermaphrodite flowers are borne on separate trees. The need for
pollination and fertilization in carob has been clearly shown by Russo (1954). This also may
be deduced from the fact that all pods contain seeds, assuming that seeds are not formed
Promoting the conservation and use of underutilized and neglected crops. 17. 55
apomictically, and that where a seed is missing the pod does not grow to its full width
(Orphanos and Papaconstantinou 1969).
The arrangement of pollinating trees in carob orchards has been traditionally
disregarded by growers. This may have caused low yield or even have contributed
to the abandonment of the crop. In the island of Crete, Sfakiotakis (1978) reported
crop failure due to unfruitfulness resulting from lack of pollination. In Morocco,
there is a project underway to graft male trees to increase pod production (S.
Padulosi, pers. comm.). Pollination has traditionally been achieved either by
keeping a male branch from the rootstock in the centre of the tree, if the rootstock
is male, or by budding a male or hermaphrodite into the tree if the rootstock is
female. Spontaneous trees (around 50% males) may be found in the
neighbourhood, near paths or tracks, but generally in insufficient number. If male
or hermaphrodite trees are planted as pollinators they must be interspersed around
and within the orchard in a regular pattern. It is important to use different types
of male or hermaphrodite pollinators to overlap with female cultivars’ bloom, as
main cultivars often display a long blooming season (3-4 months between August
and November). Since male trees have a shorter flowering period than
hermaphrodites, the latter usually show better overlapping.
Neither the optimum density of pollinators in the orchard nor the possible differences
between using males or hermaphrodites have been determined. The ideal ratio of male or
hermaphrodite to female trees presumably depends on insect and wind activity in the
orchard during flowering and also on pollen germinability. The proposed range varies from
the 4% of Coit (1949) to the 20% of Merwin (1981). However, it seems enough to plant around
12% of pollinating trees (males or hermaphrodites) (Tous and Batlle 1990), e.g. a ratio of 8
females to 1 male or hermaphrodite, with pollinators planted in every 3rd row and separated
by two female trees within the row. Additional staminate trees could also be planted in border
rows upwind of the orchard. In California, Thomson (1971) recommended an orchard
pollination design of hermaphrodites on alternate or every third row of trees for adequate
pollination. In existing groves showing pollination deficiencies, some female trees can be
top-worked and grafted with male or hermaphrodite scion wood.
12.4 Training systems and pruning
The carob tree is a species that needs little pruning, unlike other fruit and nut trees,
which require pruning annually. After the basic framework of the tree has been
established only light pruning is necessary. This fact is due to carob’s specific
growth and fruiting habits. While pruning, it is necessary to consider several
important characteristics of carob (Tous and Batlle 1990):
• its natural tendency to form a central axis with a strong prevalence of side
• fruiting on wood 2 years and older
• sensitivity to big cuts, which heal very slowly.
5 6 Carob tree.
The traditional training methods were based on usually spherical or open vase
forms, with a tall trunk and branching (first scaffold) from 1.5 m above the ground.
Currently pruning is simple and straightforward. Short trunks (low first scaffold)
favour a short vegetative (unbearing) period whereas longer trunks are advisable
for mechanical harvesting using shakers. Thus the carob should be trained
according to the harvesting system (manual or mechanical) foreseen, as free vase
or modified central axis forms, respectively.
This respects the natural shape of the young tree, pruning being very light or none
at all during the first years. It is only necessary to eliminate the shoots that come
out from around the soil and to break some of them to avoid excessive growth on
the lower branches. After fruiting, the first shaping pruning should be done. This
consists of removing the lowest branches over 2 years to produce a clean trunk of
0.5-0.7 m. With this training system small trees will develop less in height and more
in width, easing manual harvesting using poles.
Modified central axis
It consists of leaving four or five primary branches well spaced and distributed
along the axis of the trunk. The first can be located at a height of approximately 0.9-
1 m. During the first years some lower branches can have their tips clipped in the
summer, instead of being cut off totally. This training system gives a more upright
crown and is more suitable for mechanical harvesting. It is important to stake the
young trees to provide support for a number of years.
They are usually slightly pruned and this operation should be carried out only
occasionally after harvesting. Mature female, male and hermaphrodite carob trees
produce flowers on wood of all ages and require light pruning only every 3-4 years
to remove dead wood and encourage fruit-bearing wood by letting sunlight filter
into the top middle section of the tree. This operation should be carried out
particularly in years where a significant crop is expected. It is necessary to maintain
an equilibrium between vegetative growth and production and it is particularly
important to confine growth and production to the space allotted in the orchard.
For fruiting, the best time to carry out pruning is at the beginning of autumn
immediately after collecting the crop. Branches should be removed when they are
not too thick (5-7 cm diameter) and the length of the annual shoot is less than 25-
30 cm. Dead branches must also be removed as well as those which are crossed or
excessively upright growing.
Old neglected orchards or abandoned trees can be rejuvenated by thinning to
increase and regularize production. If branches are broken in gales they should be
removed with a clean cut and mastic applied to the cut surface to keep out rain as
Promoting the conservation and use of underutilized and neglected crops. 17. 57
rotting can start easily, especially in mature trees at the peak of production.
Traditionally, carob orchards have hardly been fertilized. This species has always
been considered extremely adaptable to very poor soils and only some manure,
when locally available, has been applied. However, in recent years, the revaluation
of the crop has led some farmers to apply various types of fertilizer, either mineral
Most bibliographic references highlight the benefits of nitrogen in increasing
fruit production in old carob tree plantations (Lloveras and Tous 1992; Correia and
Martins-Louçâo 1993). It has been shown that this leguminous tree is unable to fix
atmospheric nitrogen (Martins-Louçâo and Rodríguez-Barrueco 1982; Martins-
In traditional orchards (density of 50 trees/ha) with average production of
2500-3000 kg/ha, an application of 50 kg of N, 20 kg of P
and 50 kg of K
hectare can be advisable (Tous and Batlle 1990). It is recommended to apply
phosphorus/ potassium-based fertilizer and 25% of nitrogen in autumn after
harvesting. The remaining nitrogen fertilizer can be applied in February as
ammonium sulphate. In plantations receiving some irrigation, one can apply N and
K in the months of May and June which coincides with the stage of fast growth of
the fruit. It is important to stress the benefit of applying organic matter as with all
other fruit and nut trees. It is recommended to apply 30-40 kg of manure per tree,
every 3-4 years during autumn tilling.
Work on carob fertigation by Correia and Martins-Louçâo (1995) in Algarve,
Portugal, using mature trees of ‘Mulata’ and testing three levels of irrigation (0, 50
and 100%) based in water loss by evaporation, and two N amounts, as ammonium
nitrate (21 and 63 kg ha-1 year-1) per each level has shown that predawn water
potentials were always higher than -1.1 MPa. Midday leaf water potential values
presented large seasonal variations and low values independently of treatments.
The low leaf water potentials observed for fertigated trees during summer
suggested that this parameter may be related not only to the evaporative demand
but also to growth investment. The amount of fertigation was positively correlated
with vegetative growth increment and fruit production. These results also
suggested that under standard conditions in the Mediterranean region, N
applications are effective even without irrigation. In addition, the results obtained
are in agreement with the ‘water spending’ strategy proposed by Lo Gullo and
Salleo (1988) for the carob tree as a drought adaptation mechanism.
In the Mediterranean region, where water resources are scarce, irrigation is
reserved for the more profitable horticultural crops. Therefore, the carob tree is
planted in dry land. However, the availability of water is a requirement for good
production. In this drought-resistant species the supply of water should be
5 8 Carob tree.
considered as occasional irrigation and within certain limits of dose and time of the
year. Esbenshade and Wilson (1986) and Tous and Batlle (1990) observed a positive
effect of irrigation on fruit production. Some experiments on young trees also
resulted in a positive effect of irrigation on pod production (Esbenshade and
Some authors indicate that, to ensure a good harvest, approximately 500 mm of
rainfall per year are required (NAS 1979), but when rainfall is below 400 mm some
complementary water supply is required (Tous and Batlle 1990). The main periods
of irrigation in this species are considered to be spring, the beginning of summer
(probable floral induction and fast pod growth) and autumn (flowering and
accumulation of reserves).
In carob orchards without irrigation (nearly all) it is worthwhile to apply some
water with a tractor and tank in late spring and summer in the first 2 years after
planting. This watering helps the start of tree growth and cropping. In those areas
with scarce water supply, drip irrigation shows goods results. In adult orchards
with water doses of 100 mm per year, benefits are clearly reflected in the yield (Tous
and Batlle 1990).
12.7 Soil maintenance
Soil maintenance in carob orchards has traditionally been carried out by tilling
weeds to reduce evapotranspiration and improve water penetration. It is advisable
to till the soil only to 15-20 cm depth, to prevent disrupting the shallow and active
root system as this soil zone is generally the more fertile and better aired. Shallow
tillage using a harrow or a cultivator is effective. Farmers in Spain usually till three
times during the year, the first time in autumn before the rainy season starts, the
second in spring and the third when the pods starts to ripen in early summer.
In some orchards in Spain weed control is accomplished through the mixed
system of tillage and herbicide applications with good results (Tous and Batlle
1990). The most commonly used chemicals have been simazine (pre-emergent,
residual), paraquat, ammonium glyphosinate and glyphosate (post-emergent). It
is advisable to avoid the application of residual herbicides before the 4th or 5th
year. Weed control is especially important in young plantations, since heavy weed
competition for water and nutrients can significantly reduce tree vigour and
12.8 Pests and diseases
The carob tree is normally free from severe insect and disease troubles and is a crop
which traditionally has not been sprayed. In Spain, the most damaging insect is the
polyphagous larva of the leopard moth (Zeuzera pyrina L.) which attacks the wood
of trunk and branches, causing severe damage to young trees. Cultivars tested in
Spain were all susceptible to various degrees (Martorell 1987; Tous and Batlle 1990).
In isolated cases, it can be controlled by introducing a wire into the galleries to
destroy the larvae or by filling the holes with pesticide paste.
Promoting the conservation and use of underutilized and neglected crops. 17. 59
The pods of many cultivars sometimes become infested with the small and
polyphagous larva of the carob moth (Myelois ceratoniae Z.) while maturing and
before harvest is complete. It also attacks stored carobs extensively where it can
be controlled by fumigating. Coit (1961, 1967) reported different susceptibility of
several cultivars to the carob moth in California. Black aphids attack mainly the
terminal shoots of young trees, and some hermaphrodite cultivars appear to show
more susceptibility than females (Tous et al. 1996). In Cyprus, Orphanos (1980)
reported carob midge (Asphondylia spp.) attacks on pods at a very early stage, which
caused stunting. High humidity seems to soften the pods, making entry by worms
The mildew disease caused by Oidium ceratoniae C. attacks pods, leaves and
twigs in different periods of the year, mainly in spring and in autumn. Severe
damage occurs only in some cultivars. For example, ‘Rojal’, ‘Matalafera’, ‘Amele
di Bari’ and ‘Racemosa’, are fairly resistant to this disease while ‘Negra’, ‘Melera’,
‘Costella’, ‘Santa Fe’ and ‘AA-2’ are susceptible (Goor et al. 1958; Graniti 1959;
Martorell 1987; Tous and Batlle 1990). Thus a cultivar grading to Oidium
susceptibility exists. Another fungus, Polyporus sulphureus, can destroy branches in
old trees. Young carob trees growing under greenhouse conditions have shown
resistance to root rot caused by Armillaria (A. mellea and A. obscura) infection (Loreto
et al. 1993).
Other pests that occasionally cause severe damage to carob orchards are small
rodents like gophers (Pitymys spp.) and rats (Rattus spp.). Gophers can severely
damage the root system of young trees. In California, Thomson (1977) reported
that it was almost impossible to establish a young orchard unless gophers are
controlled. In Cyprus (Orphanos 1980) and other Mediterranean countries, rats are
major pests. Rats can strip the bark not only of young shoots but also of older shoots
and even limbs and by girdling a limb or branch can kill it. Several types of baits
in traps can be used to control these rodents. However, the best control is natural
predation by the wild native fauna, conservation of which is essential. Cattle,
horses, sheep and goats all browse on the foliage of young and adult trees and can
kill young unprotected trees.
Carob orchards are known to enter slowly into production. This has two main
causes: the slow growth of the tree and its long vegetative period, and other
environmental and cultural factors. In plantations located in marginal areas, the
nonbearing period is long, from 6 to 8 years, while in others, where the conditions
are better, cropping starts 3 or 4 years after budding. The production increases to
achieve full bearing at 20-25 years of age and then stabilizes (Batlle 1985). Goor et
al. (1958) reported that carob trees start to bear fruit in the 5th to 6th year when
budded trees are planted and in the 7th or 8th year when seedlings are used for
planting and later budded.
It is also important to recognize that carob shows alternate or biennual bearing.
6 0 Carob tree.
The causes, in addition to genetics include climatic conditions such as scarce and variable
rainfall, frost, fog, lack of pollination, damage of the inflorescence during harvesting
(knocking down of the fruit), and deficiencies in orchard management (fertilization,
pruning, etc.). Haselberg (1996) in Algarve, Portugal, has observed in 30 to 40-year-old
‘Mulata’ trees that the presence of pods in ‘on’ years has an inhibitory effect on the current
season’s flower differentiation, mainly during the period of most intensive fruit and seed
growth (April to June).
The productive potential of the carob is variable and scarcely known under good
cultivation conditions. In Spain, average orchard productivity is around 1500 kg/ha
(MAPA 1994), which can be regarded as very low. In Portugal, the average yield is 1700-
2700 kg/ha (Droste 1993). In Tarragona, Spain, orchards which receive minimum
management tend to produce 2000-3000 kg/ha, giving an average yield of 50-70 kg per tree.
Some modern orchards 10 years old in Spain and Portugal give high yields, about 5000 kg/
ha in dry conditions and 7000 kg/ha with deficit irrigation (Tous et al. 1993). In Israel, on
fully bearing trees in nonirrigated groves but with 550 mm of annual rainfall the yield can
be about 7400 kg/ha and in irrigated orchards an average of 12 300 kg/ha can be reached
(Goor et al. 1958). A well-grown adult tree could yield about 100-200 kg/year. Some big
isolated trees can produce 250-300 kg in exceptional years.
Carob harvesting is usually carried out at the end of summer or the beginning of
autumn depending on cultivar and region. Harvesting can be manual or
mechanical. In Mediterranean countries, carob groves are mainly hand-harvested
by knocking down the pods with the help of long bamboo poles or wooden sticks
and collecting them on fibre nets which are laid out under the trees. This operation
needs careful handling since at this time of the year the carobs are in full bloom. The
striking action of the poles can damage flowers and the next crop might be partially
destroyed. This task constitutes the most significant part of the total cost of
cultivation since it r
equires much hand labour, being currently about 30-35% of the total
production costs (Orphanos 1980; Tous 1995b). In Spanish orchards the quantity of pods
manually harvested, in average crop years, varies between 250 and 280 kg/day per worker
(Tous and Batlle 1990). Mechanical harvesting using trunk or branch shakers has not been
practised in most producing countries, mainly because of the small size of most orchards.
However it seems feasible to adapt conventional harvesters used fo
r other tree crops
(olive, almond, pistachio, walnut, etc.) as carob branches are thick and stiff. To
reduce harvesting cost, pods of a given cultivar should all be harvested at one time.
Fruit ripeness, and therefore its optimal harvesting time, is indicated by the
complete darkening of the pedicel just prior to natural detachment from the branch.
This is a reliable sign that pods are ripe and have reached their full sugar content.
Sometimes pod drop is hastened by the wind. Carobs should be harvested when
they have 12-18% water content. After harvesting, carobs are either delivered to
the processor or stored under shelter. Moisture will gradually decrease during the
subsequent months of storage.
Promoting the conservation and use of underutilized and neglected crops. 17. 61
Most of the carob pods harvested are brought to the processing plant. When carobs
arrive, moisture content is variable (10-20%) depending on harvesting conditions
and autumn rainfall. Pods require further drying and thus are stored under shelter
in dry and ventilated places to reduce moisture to around 8% and to avoid rotting.
Insects in stored carobs, mainly carob moth, can be controlled by fumigation. Pods
are kibbled to separate the two main components: pulp and seeds.
Carob pods are crushed mechanically using a kibbler, then are separated from
the kernels. The processing of the carob beans and the products obtained are
shown in Figure 13. This first coarse grinding can be followed by fine grinding of
the pod pieces (kibbles) either at the same plant or at the feed or food factories. The
feed factory grinds the deseeded pulp to different sizes in relation to the kind of
livestock to be fed. The food industry processes the pulp further by roasting and
milling to obtain a fine powder which is traded as carob powder.
The carob seeds are transported in bulk by lorry to the gum factories. The
kernels are difficult to process, since the seed coat is very hard. Kernels are peeled
without damaging the endosperm and the embryos (germs). The two main
procedures applied to remove seed coat are: acid (seeds treated with sulphuric acid
to carbonize the coat) or roasting (kernels roasted in a rotating furnace to peel off
the coat) (Puhan and Wielinga 1996). After the peeling process the endosperm can
be split from the cotyledons because of their different friabilities. When the peeled
Fig. 13. Processing of the carob pod.
Pods Kibblers Kernels
Crushed and deseeded pulp (90%)
6 2 Carob tree.
seeds are forced through a splitting machine the brittle embryos turn out as a fine
powder (germ meal) and can be separated from the unbroken endosperm scales by
a sifting operation. Subsequently the endosperm is ground on roller mills to the
desired particle size (gum). The carob bean gum is the ground endosperm and the
carob germ meal is a by-product of the seed processing.
Grower payout is calculated more and more in relation to the kernel yield of
the cultivar delivered and also on amount of debris. Before carobs are stored, a
grading sample is drawn from each delivery. This sample is processed individually
using a small kibbler to determine kernel percentage. The two major components
in determining return to the grower are weight delivered and percentage by
weight of kernels.
Promoting the conservation and use of underutilized and neglected crops. 17. 63
13 Limitations of the crop
There are factors limiting the planting of carob in new areas, especially insufficient
cold-hardiness, and factors limiting the profitability of the crop in existing areas,
in particular factors that determine the suitability for modern orchards. In addition
external economic factors limit the crop.
Carob’s main limitation is insufficient cold-hardiness. A frost of -4°C or below may
damage or kill young trees or even shoots, flowers and young fruits in mature trees
(Tous and Batlle 1990). A more severe frost can kill adult trees as has occurred
several times in the Mediterranean region (in 1956 and 1985). Generally, carobs
should not be planted above 500 m of altitude or in places where risk of frost is high.
Acclimatization to low temperatures requires days to weeks for maximum chilling
stress tolerance to develop. Photoperiod also seems to be involved in the
acclimatization process in carob as in many other evergreen species.
13.2 Suitability for modern orchards
The main aim of new carob orchards should be to maximize seed production per
hectare. Ideally cultivars should combine high seed yield and high productivity.
However, useful cultivar information is only partially available. As the main labour
requirement in carob groves is harvesting, efforts should be addressed to reduce
this input which represents 30-35% of the total management cost (Orphanos 1980;
Tous 1995b) and thus cultivars that ripen uniformly and are easy to shake should
be used for mechanical harvesting.
13.3 Market situation
From the market situation over the past 15 years it can be seen that carob pod prices
tend to be cyclic with long gaps, and high peaks as in the years 1984 (US$0.25/kg)
and 1994 (US$0.80/kg). This makes the market unsettled and produces a negative
effect on demand. In addition, highly variable prices favour market speculation.
However, the industry needs a steady and regular raw supply and stable prices on
which customers can rely. In addition, carob seed prices are even more fluctuating
than carob kibble prices. As the main industrial application is the CBG this recurrent
situation affects carob demand and thus its multiple uses. Big fluctuations in carob
seed prices should be avoided in the future.
6 4 Carob tree.
Since the start of the 1980s this crop has raised a considerable interest because of
generally sustained demand and increasing prices of the carob pods (pulp and
seed). However, this trend has been sharply modified twice in the last 10 years:
in 1984-85 and 1994-95 when prices peaked. The high pod prices led to a loss of
competitiveness of the carob bean gum versus other natural (guar and tara) or
artificial hydrocolloid substitutes, both times producing a subsequent decline of
Carob price stabilization in the market would improve the future outlook of this
crop. The revaluation of the carob pulp in animal feeding and carob powder as
human food, could help to increase its demand and then to reduce the final
dependency of the pod price on the kernel. In addition the ‘healthy’ and ‘light’
component of derivatives of the carob pulp (confectionery, bakery and drinks)
should be fully explored.
The carob tree shows some outstanding features like rusticity, drought
resistance, reduced orchard management, etc. and it is also well suited to part-time
farming. In addition, modern carob orchards start bearing earlier (4th year after
budding) than traditional ones and increase their yield steadily in response to
minimum cultural care and lack of irrigation. The development of a useful method
of propagation by cuttings would have a favourable impact on carob growing.
Agricultural sustainability has been increasing in importance over the years.
Although carobs produce reduced yields in old plantations (1500-3000 kg/ha), in
modern orchards production potential is higher (5000-7000 kg/ha). In addition, in
optimum conditions carob requires a minimum of inputs compared with most other
fruit, nut or vegetable crops. In many semi-arid regions and marginal soils where
carob is well adapted and cultivated, the quantity and quality of irrigation water
are major limitations to production. This crop has received little attention until now
but is currently being re-emphasized as an alternative in dryland areas with
subtropical Mediterranean climates for diversification of coastal agriculture.
Although it seems that the overall world carob production trend is rather
stationary (Tous and Ferguson 1996; Batlle 1997) some countries will continue to
reduce their production while a few will probably increase theirs. Production in
Morocco is likely to increase in the coming years to supply its local industry for gum
extraction which benefits from low labour costs. Australia also seems to be a future
potential producer of pods, mainly for livestock feeding in agroforestry systems
(Esbenshade and Wilson 1986; Tous 1995a; Race and Curtis 1996).
Another factor to be considered is that the total harvested carob production is
partially affected by the price level. It was assessed in commercial groves in Sicily,
Italy by Licitra (1996) that 10-15% of the whole production is only collected when
pod prices are rewarding for growers and even more than 50% on spontaneous
isolated trees. The main production is usually harvested every year. This is also
happening in some other Mediterranean growing areas.
Promoting the conservation and use of underutilized and neglected crops. 17. 65
The reviewed information on genetic resources shows that carob cultivars
vary widely in many characteristics, such as yield, season of maturity,
susceptibility to pests, precocity, ease of harvest, sugar content, kernel yield, gum
content and quality.
Most CBG factories are placed in Mediterranean countries of the European
Union (EU) (Spain, 5; Portugal, 2; Italy, 1) as this is the leading world carob-
producing region and is expected to remain so in the future. However, newly
established industries are operating in developing African countries like Morocco
(which has 2). There is also a small processing plant in Turkey. The current CBG
world demand by the food and pet food industries of around 15 000 t should be
supplied yearly; otherwise, the consumer industry will change to other gums with
a consequent loss of market. Although supply and demand of CBG show some
flexibility annually (around 2750 t), any market loss is usually hard to recover.
One strength in the carob sector is that it is fairly well organized in the main
producing countries. Thus although growers, cooperatives, kibblers, factory
managers, the agrofood industry and R & D institutions have some different
interests, all rely on proper prices for pods and kernels and are aware that a better-
organized sector (from producer to consumer) would be mutually beneficial. Most
of the companies that produce carob bean gum have belonged since 1972 to the
Institut Europeen des Industries de la Gomme de Caroube (INEC) which is located
in Brussels, Belgium. INEC has a Technical Committee and a Secretariat General
which is based at ETH in Zürich, Switzerland.
INEC was launched by most of the important producers of CBG as a
cooperative nonprofit organization to meet the extensive toxicological
investigations requested by the FAO/WHO and the EU on food additives to be
considered harmless. The INEC could play an important role in supporting studies
on production and application of the CBG as the natural gum with best properties
for the food and pharmaceutical industries. In addition, the INEC could foster
programmes to conserve the carob crop and develop crop technology, encourage
new plantings in developing regions, and improve the use and economics of carob
At present, it is mainly growers of Spain, Portugal, Greece and Italy who seem
to be interested in carob as a crop. Most remaining Mediterranean countries
maintain carob as a native tree, useful environmentally and for landscape
recreation. Currently, this tree crop is included in the EU aid programme. Actions
are considered in the Nut and Carob Production Organizations scheme (European
Regulation number 2159/89). In addition, the carob tree was included in forestry
actions of the EU (European Regulation number 2080/92).
A decision to establish, expand or replant a carob orchard requires knowledge
of current and potential consumption (domestic and abroad) and price evolution
(variability and projection). It is also important to know competition and market
volatility. Its future possibilities in an ever-more competitive horticulture with
increasingly low inputs (labour, water, fertilizers, sprays, etc,) are promising
6 6 Carob tree.
provided that the CBG market prices stabilize. Production costs can be reduced by
increasing the ease of harvest. In addition, its use as an ornamental species for
xerogardening and for landscaping is increasingly being recognized.
An interesting initiative to promote carob growing was the establishment of the
Associaçao Interprofissional para o Desenvolvimento da Produçao e Valorizaçao
da Alfarrova (AIDA) in 1985 in the Algarve, Portugal. This independent association
brings together efforts of interested people and institutions involved in carob
production, processing and marketing.
Promoting the conservation and use of underutilized and neglected crops. 17. 67
15 Research needs
Carob has been traditionally neglected by Research & Development programmes
so that knowledge about existing cultivars in the Mediterranean region is still poor.
Centuries of carob cultivation have given rise to a number of cultivars differing in
agronomic characters, and large natural populations remain untouched in countries
like Morocco and Turkey as described in the Genetic Resources section. Thus
surveys and a cooperative project to compare and characterize most useful cultivars
and types selected from the wild are much needed.
In 1973, the Mediterranean Group for Applied Plant Physiology (MPP) chose the
carob tree as a suitable Mediterranean species meriting R & D effort to improve the
knowledge of its physiology and environmental adaptation. Since this initiative,
three International Carob Symposia have been held with the participation of
physiologists, pomologists, chemists, pharmacists and processing managers. As
the main group involves physiologists, the main output has been on physiology-
These three Symposia were held in 1978 in Aldeia das Açoteias, Portugal
(Catarino 1980), in 1987 in Valencia, Spain (Fito and Mulet 1988), and in 1996 in
Cabanas, Portugal. It is clear that the knowledge on genetic resources,
propagation, agronomy, potential productivity, agroforestry, afforestation and
uses of carobs is still too limited compared with other Mediterranean tree species.
In 1986, a meeting was held in INIA Oeiras, Portugal on carob research activities
in which the main working lines of several research groups from some producing
countries were discussed (Brito de Carvalho 1988b).
Work on characterization and documentation of carob cultivars is scarce
worldwide (Grainger and Winer 1980). In addition to some classic work by Russo
(1954) in Italy, Coit (1967) in California, Orphanos and Papaconstantinou (1969) in
Cyprus and Vardar et al. (1980) in Turkey, some countries like Italy, Portugal and
Spain have recently made surveys on their native genetic resources and collected
material to be studied and conserved in collections and genebanks (Tous et al. 1996).
The carob research programme at IRTA-Mas Bové was started in 1984 (Batlle and
Tous 1988), after a wide survey of the carob native genetic resources and
possibilities of this crop in Catalonia had been carried out by Batlle (1985).
Although several descriptors outlines have been proposed for carob (Coit 1949;
Russo 1954; Donno and Panaro 1965; Batlle 1985; Brito de Carvalho 1988a;
Crescimanno et al. 1988; Tous et al. 1996) the development of a generally accepted
scheme for cultivar characterization and evaluation, ideally with the support of
IPGRI, is much needed. It would be possible for IRTA to take this initiative. A good
starting framework for a descriptor list would be the last scheme proposed by Tous
et al. (1996) which is presented with some modifications in Appendix III. Passport,
management, and environmental and site descriptors are omitted.
In the existing carob collections it seems that enough genetic diversity exists for
crop improvement. However, as the main use for carob pods is currently the seeds,
whereas most cultivars maintained in collections were selected for high pulp
6 8 Carob tree.
content, it is worth selecting and collecting more wild types with high seed yield
and characterizing/evaluating them in orchards. A survey of isoenzymes or other
molecular markers in appropiate populations will allow the level and distribution
of genetic diversity within and between the two Ceratonia species to be estimated.
This is of potential interest if the two species hybridize. It could be interesting to
compare diversity of cultivars with diversity in the wild. It could also help to locate
species polymorphism for collecting and conservation. A marker for sex also would
be useful if carob breeding is attempted.
Although progress has been made on carob propagation by cuttings (Alorda et
al. 1987; Alorda and Medrano 1988; Cabrita et al. 1988; De Michelle and Occorso
1988), efforts are needed to transfer this technique to the nursery industry. A simple
and cheap method for producing trees by cuttings would make budding
unnecessary and might provide a shorter vegetative period.
Pollination in carob either by insect or wind is not yet clearly understood. It
is a key component of orchard design and production and consequently should be
studied further. A wide range of flowering types (male and hermaphrodite) should
be included in any work to be carried out. Pollen germination tests (in vivo and in
vitro) are necessary to select and propagate male and hermaphrodite pollinators. In
addition, flower induction is a critical step for fruit production and thus for orchard
management but is poorly understood and needs to be studied in the near future.
More information is also needed on tree density and potential yield. The
precise nutrition and water requirements of the carob are yet to be determined. In
addition, more research work on carob cambial activity and potential differences
between cultivars and sites, under irrigated and nonirrigated conditions, is needed
to schedule water supply and stop growth before winter.
Alternate or biannual bearing causes problems for both farmers and the stock
market. CBG factory managers need to know every year the potential carob pod
production to plan their purchases. Thus developing techniques for early
assessment of the anticipated production is of particular interest to CBG factory
operators. So the companies which belong to INEC might be interested in
collaborating on projects to forecast carob yield (e.g. from pollen fluxes,
meteorological data, etc.) in the future.
The use of carob for afforestation and soil conservation in warm Mediterranean
areas with degraded vegetation or to prevent erosion is often raised but has not
yet been investigated. It seems that carob is not a forest species as it thrives in the
maquis; however, its role and potential suitability to cover bare land will be worth
assessing. In addition, its response to fire, which is common in the Mediterranean
region, is unknown. Sprouting ability would be a determining factor in natural
regeneration. The carob tree showed some regeneration capacity after aerial
killing by deep frost (-15°C) on the Mediterranean Spanish coast in 1956 and 1985
(Batlle 1985). As carob cannot withstand competition with other forest and maquis
trees and shrubs, its germination in nature is rare. It thrives well and regenerates
by seeds on dry and warm sites in Israel (Liphschitz 1987). The development of
Promoting the conservation and use of underutilized and neglected crops. 17. 69
mycorrhiza inoculation in carob nurseries could improve the establishment and
growth of new orchards and afforestation plantings.
To summarize, the research needs for carob improvement are:
• development of a descriptor list
• characterization and evaluation of existing collections
• selection of promising wild types (female and hermaphrodites)
• development of a useful method of propagation by cuttings
• pollination studies (insects and wind)
• tree density and potential yield
• reforestation capacity.
7 0 Carob tree.
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Appendix I. Cultivar description
A description of the main features of 27 carob cultivars from 6 different countries
is presented (Cyprus 3, Italy 6, Portugal 2, Spain 11, Tunisia 1 and USA 4).
The information given has been reported by Orphanos and Papaconstantinou
(1969), Ticho (1958), Coit (1967) and Orphanos (1980). Three types of carob trees
are distinguished by growers according to Orphanos and Papaconstantinou (1969):
Agria and Apostolika are wild and ungrafted and ‘Imera’ are grafted trees. Within
grafted types, three cultivars are described: ‘Tylliria’, ‘Koundourka’ and
Origin Cyprus (unknown).
Synonyms ‘Saradjinica’, ‘Vakles’ or ‘Vaklaes’.
Tree vigorous and upright habit, reddish twigs and large leaves.
Growing area all over the island, is the main cultivar grown in Cyprus.
Pods 15-17 cm long, slightly curved, colour reddish brown, width 2-2.5 cm,
thickness 1-1.2 cm. The seeds are relatively flat and smooth. Seed
content is around 8% (7.6%-10.6%). The flesh contains 51% sugar
and the seeds contain 49% gum.
Remarksit is not early cropping; it can be harvested early although the pods remain
on the tree after maturity. Its production in Cyprus is mainly for
export; excellent quality for milling; it was introduced in some
other countries, like Greece, Israel and the USA; several slightly
different types have been described (Ticho 1958).
Origin Cyprus (unknown).
Growing area Karpass peninsula in Cyprus.
Tree medium size with weeping habit.
Podsdark brown, normally straight and relatively short (about 13 cm). The side
towards which the seeds are pointing is thicker than the other side
(thickness: 0.97 and 0.73 cm, respectively). The seeds show an
angular shape and are thicker than ‘Tylliria’ seeds. The seed
content is about 14-15%. The flesh contains 50% sugar and the gum
content of the seed is 58%.
Remarks early maturing, pods shedding on maturity. Interesting cultivar, as it
combines medium tree size, high seed content and self-shedding
of the mature pods.
Origin Cyprus (unknown).
Growing area Karpass peninsula in Cyprus.
Podsdark brown and long (about 20 cm), and curved towards the narrow side. The
side toward which the seeds are pointing is thicker than the other
side (1 wide and 0.76 cm thick). The seeds are relatively flat and
slightly uneven. The flesh contains about 53% sugar and the seeds
yield 53% gum.
Remarks early maturing.
The information given has been reported by Russo (1954), Donno and Panaro
(1965), Spina (1986) and Crescimanno et al. (1988).
Origin Sicily, Italy.
Growing areas it is grown mainly in Ragusa and Siracusa districts, Sicily.
Synonyms ‘Latinissima’ and ‘Cipriana’.
Treevigorous with open growth habit and with lower branches bent towards the
ground. Leaflets of medium size.
Podsdark brown colour with curved shape, rough surface, medium size (16 cm), 2.5
cm wide and 1 cm thick. The pulp has a sugar content of 38-40%
and seed yield is about 8-10%.
Remarks it is a productive cultivar and shows low alternate bearing.
‘Amele di Bari’
Origin Bari in Apulia, Italy.
Growing area district of Apulia, Italy.
Synonyms ‘Amele’ and ‘Mele’.
Tree vigorous with upright growth habit and with dense branching and small
Podsdark brown colour with straight shape and rough surface, medium length (15-
19 cm), 2.3 cm wide and 1 cm thick. High pulp content of light
brown colour and with high sugar content (53%). Seed yield is low
Remarksit is a productive cultivar although it shows alternate bearing. It shows
low susceptibility to Oidium.
Origin Sicily, Italy.
Growing area Sicily.
Synonyms ‘Moresca’, ‘Carruba Spada’ and ‘Sciabulara’.
Treeless vigorous than other Italian cultivars. Long leaves of light green colour.
Podsdark brown colour of short length (13 cm), 2.3 cm wide and 0.9 cm thick. Seed
yield is low (7.5%).
Origin Sicily, Italy.
Growing area Sicily.
Synonyms ‘Latina’, ‘Fimminedda’ and ‘Milara’.
Tree vigorous with upright growth and dense foliage. Leaflets of small size.
Podslight brown colour of medium length (15-16 cm), 2.6 cm wide and 0.8 cm thick.
Seed yield is low (9%).
Origin Sicily, Italy.
Growing areas eastern Sicily.
Tree upright habit and medium leaf size
Pods dark brown colour and mostly straight, length 13-15 cm, width 2 cm. Seed
yield is low (6%). Flesh flavour is fair.
Remarks crops when young; ripening in September-October.
Origin Sicily, Italy.
Growing area Agrigento, Sicily.
Tree open habit and small leaves.
Pods dark brown colour, seed yield is medium (12%).
The information provided has been reported by Da Matta (1952), Haselberg (1988)
and Tous et al. (1996). There are many Portuguese cultivars: ‘Mulata’, ‘Galhosa’,
‘Canela’, ‘Costela de Vaca’, ‘Alfarroba de Burro’, ‘Castiça’, ‘Roxa’, ‘Lisa’, ‘Parda’,
‘Da Lapa’, ‘Brava’ ‘Bonita’, ‘Gasparinha’ and the recently selected ‘AIDA’.
Origin Algarve, Portugal.
Growing areas Algarve region, Portugal.
Treevigorous with open growth habit and with big leaflets of dark green colour.
Podsdark brown colour with straight shape, rough surface and medium length (14-
17 cm), 2 cm wide and 0.9 cm thick. The pulp has a high sugar
content and seed yield is medium-high (12-14%). The seeds
contain 55.8% gum.
Remarksit is a very productive and early maturing cultivar and well regarded in
the Algarve district. It shows low susceptibility to Oidium.
Origin Algarve, Portugal.
Growing areas Algarve region, Portugal.
Tree vigorous with open growth habit and with leaflets of light green colour.
Podsare reddish to brown colour and 15-17 cm long. Seed yield is high (15-17%).
The seeds contain 58.3% gum.
Remarks late bearing age. Low susceptibility to Oidium. Commercially it is an
The information presented has been compiled from Caja et al. (1984), Batlle (1985),
Tous (1985), Martínez-Valero et al. (1988), Batlle and Tous (1990), Tous and Batlle
(1990) and Tous et al. (1996). The described cultivars are arranged in order of
Origin Spain (unknown).
Growing area Barcelona, Tarragona and north of Castellón.
Synonyms ‘Negreta’, ‘Negral’ and ‘Del país’.
Treevigorous with spreading growth habit and dense branching. The leaflets are
Podsblack and straight, with rough surface, short (13-16 cm), around 2.5 cm wide
and 1 cm thick. The pedicel is short. The flesh is white, of good
quality with a high sugar content and it has a low seed yield (7-9%).
Remarksit shows alternative bearing mainly if cultural practices are not carried out
well. Late maturing. Resistant to fruit shedding and tends to
produce small beans. It is susceptible to Oidium and Zeuzera. Good
cultivar for animal feeding. It is the main Spanish cultivar with
production of over 24 000 t/year.
Origin Spain (unknown).
Growing area mainly Valencia and Alicante.
Treemedium vigour with open growth habit. Sparse branching and foliage with
smooth and straight branches. Large leaflets. Pods are produced
Pods dark brown colour and slightly curved, smooth surface, 16-18 cm of long,
about 2.3 cm wide and 1 cm thick. Flesh content is high and its seed
yield is medium (11-12%).
Remarks productive and shows low alternate bearing, mainly if it is grown on
fertile soils. Low susceptibility to Oidium. It is interesting for its
good commercial features. Around 13 000 t/year of this cultivar
Origin Majorca, Spain.
Growing area is grown mainly on the sunny slopes of the northern range (Sta.
María, Consell and Alaro) in Majorca and also in Ibiza, Spain.
Synonyms ‘De Durayo’, ‘Duraiona’ and ‘Uraiona’, Ibiza.
Tree medium vigour, weeping growth habit, dense branching and slow growth.
Young branches are smooth and older ones have knots. Leaflets
are large, of a faint green colour.
Podsreddish to brown colour, slightly curved, rough surface, 15-17 cm long, 2 cm
wide and less than 1 cm thick. The pedicel is long. Its seed yield
is high (15-16%).
RemarksProductive, sensitive to frost. Shows medium resistance to Oidium. It is
an interesting cultivar for new orchards (early and regular
cropping). Some 9000 t/year are produced.
Origin Vilaseca, Salou and Cambrils, Tarragona, Spain.
Growing area mainly Camp of Tarragona district, Tarragona.
Synonyms ‘Roja’. It is often locally misnamed ‘Valencià’ or ‘Valenciana’.
Treevigorous with upright growth habit and dense branching. Smooth trunk and
branches. Foliage is dense and leaflets dark green.
Podsreddish, curved with smooth surface, 17-20 cm long, around 2 cm wide and
about 0.9 cm thick. The flesh content is medium and seed yield is
Remarksproductive and regular bearing, early cropping. Low resistance to fruit
shedding. Low susceptibility to Oidium. Shows some tolerance to
low temperatures because of its dense foliage. An excellent
cultivar for its agronomic and commercial characteristics. It is the
main cultivar used for new orchards in Tarragona, Spain.
Origin Murcia, Spain.
Growing area south of Alicante and Murcia.
Tree very high vigour.
Podsbrown colour, 16-22 cm of long. The pulp is faint and with high sugar content.
Seed yield is low, 6-7%.
Remarks heavy alternate bearing.
‘De la Mel’
Origin Artá, Majorca, Spain.
Growing areais grown in Palma, Puigpunyent, Establiments, San Sardina, Santany,
Tree vigorous spreading growth habit and dense branching and fast growing.
Branches have knots. Dense foliage. The leaflets are small and of
dark green colour.
Pods dark brown colour, straight and rough surface, medium length (13-18 cm),
around 1.75 cm wide and 0.6 cm thick. The flesh has a high sugar
content and seed yield is high (13-16%).
Remarks shows alternative bearing, is medium harvesting.
‘Banya de Cabra’
Origin Garraf district, Barcelona, Spain.
Growing area mainly Garraf, Barcelona.
Tree vigorous with weeping to open growth habit and intermediate branching.
Large leaflet size and long inflorescences (9-11 cm).
Podsbrown colour and twisted with very rough surface, 18-20 cm long, about 2 cm
wide and 0.7 cm thick. They have a low pulp content and a high
seed yield (13-14%).
Remarksproductive although it shows alternate bearing. Low resistance to fruit
abscission. Medium susceptibility to Oidium. It is considered more
frost tolerant than other Spanish cultivars. Commercially it is an
Origin probably Valencia, Spain.
Growing areas Castellón, Valencia and Alicante, Spain.
Tree vigorous with upright habit and slender twigs, to leaflets.
Podsbrown colour, medium length (12 cm) mostly straight. Width is 1.5 cm and valley
is 0.5 cm. Smooth surface and distinct creases. The pulp has a high
sugar content (51-56%) and fair flavour. The seeds are round.
Remarksit is a very old cultivar, long grown in Spain. Precocious, good yielding and
with ready pod abscission at harvest in September. It was
introduced in the USA.
Origin Murcia, Spain.
Growing area south of Alicante and Murcia.
Tree medium vigour with weeping growth habit and sparse branching.
Podsbrown colour, curved and rough surface, produced on clusters, 15-20 cm long
and around 2.3 cm wide. The flesh and sugar content are high and
seed yield is medium-low (8-10%).
Remarks self-fertile and early cropping, productive although shows alternate
bearing and early cropping and easy harvesting. Medium
susceptibility to Oidium. It is the main cultivar used in new
orchards of its traditional growing area.
Origin Castellon, Spain.
Growing area Castellón.
Tree vigorous with spreading growth habit and dense branching.
Podsdark brown colour, 15-16 cm long, around 2.1 cm wide and 1 cm thick. The pulp
content is medium and seed yield is medium (11-12%).
Remarks productive and regular bearing, early cropping. Shows medium
resistance to Oidium.
Origin Murcia, Spain.
Growing area South of Alicante and Murcia.
Tree medium vigour.
Podsbrown colour, curved and rough surface, 14-18 cm long. Seed yield is medium
Remarks tends to alternative bearing.
The information gathered is from Crossa-Raynaud (1960), Coit (1967), and Brooks
and Olmo (1972). Only one named cultivar, ‘Sfax’, is reported in Tunisia.
Origin likely Menzel bon Zelfa or Sfax (Tunisia).
Growing areas several districts in Tunisia.
Tree vigorous with exceptionally spreading (open) habit; twigs very thick and
reddish. Large leaflets.
Podsreddish brown colour, straight or slightly curved, long length (15 cm), 2 cm
width, valley 0.6 cm, surface rough. The seeds are elliptic. The
sugar content of the flesh is 45-56% and has excellent flavour. Seed
yield is medium (10-12%).
Remarks fairly precocious and yield medium heavy, regular. Early ripening and
good pod abcission.
The carob tree was likely introduced into the United States from Spain by the US
Patent Office in 1854. In the 1950s W. Rittenhouse and J.E.Coit promoted this
species in California and introduced budwood of selected cultivars from Cyprus,
Israel, Tunisia, Greece, Yugoslavia, Creta, Portugal, Italy and Spain. In addition,
seedling trees grown for shade on the streets of cities in Southern California and
Arizona were selected for their floral and fruit characteristics for commercial
production (Condit 1919; Coit 1949, 1967; Schroeder 1952; Coit and Rittenhouse
1970; Brooks and Olmo 1972). A few of these selections are described.
Origin Santa Fe Springs, California.
Growing area California.
Tree open habit with slender reddish twigs, 8-10 leaflets per leaf.
Pods light brown colour, slightly curved and often twisted, 18-20 cm long; 2 cm
wide; smooth surface. The sugar content of the flesh is around 47%
and has excellent flavour. Seeds are elliptic. Seed yield is medium
Remarksprecocious cultivar and pod abcission is fair. It yields well and regularly.
High susceptibility to Oidium.
Origin Corona, California.
Growing area California.
Tree upright and compact habit, 7-10 leaflets per leaf.
Podslight brown colour and slightly curved, short-medium length 13-16 cm, width
2 cm, smooth surface. The flesh has a high sugar content (around
52%) and fair flavour. The seeds are elliptic.
Remarks precocious cultivar and heavy and fairly regular bearer.
Origin Rialto, California.
Synonyms ‘Horne’ and ‘Nichols’.
Growing areas California.
Podsshort 12-15 cm, rather plump. The flesh has a medium sugar content (around
Remarks tree bears well and is self-fruitful.
Origin Bari in Apulia, Italy.
Growing areas and synonymswas commonly grown on the Adriatic Coast under
Remarksmale type selected as pollinator due to its abundance of staminate flowers.
It blooms very heavily, but too late to pollinate some early
blooming female cultivars in California.
Appendix II. Centres of research and genebanks
The main institutions and research centres working on carob tree or holding genetic
resources are as follows.
Institute/Research Centre Main research
International Tree Crops Institute Cultivar evaluation,
PO Box 929 agricultural management
Nedlands 6009 and agroforestry
Expert: H.W. Esbenshade
Loxton Research Centre Cultivar collection
PO Box 411
Loxton, S.A. 5333
Tel: +61-85-859100. Fax: +61-85-859190
Curator: F. Hobman
Agricultural Research Institute Plant material and orchard
PO Box 2016 management
Tel: +357-2-305101. Fax: +357-2-445156
Working team: P. Orphanos and C. Gregoriou
Institute of General Botany Cultivar evaluation, pulp
Biology Department sugar and CBG quality
Tel: +30-1-7284653. Fax: +30-1-7234136
Working team: S. Marakis and C.G. Spyropoulos
Istituto di Coltivazioni Arboree (ICA) Cultivar evaluation and
Università degli Studi di Palermo physiology of reproduction
Viale delle Scienze 11
90128 Palermo (Sicily)
Tel: +39-91-423398. Fax: +39-91-6521098
Working team: F.G. Crescimanno
and R. Di Lorenzo
Associaçao Interprofissional para o Cultivar collection
Desenvolvimento da Produçao e Valorizaçao (Castro Marim-Tavira)
da Alfarroba (AIDA) Cultivar evaluation,
Loteamento Industrial de Loulé propagation, agricultural
Apartado 302 techniques (irrigation,
8100 Loulé (Algarve) fertilization, planting
Tel: +351-89 415151. Fax: +351-89-415494 density, etc.)
Working team: J.M.V. Graça, P. Correia
and P. Barracosa
Departamento de Biología Vegetal Plant crop physiology,
Facultade de Ciencias de Lisboa biological studies
Campo Grande Bloco 3 Piso 4 and fertilization
Tel: +351-1-7573141. Fax: +351-1-75800048
Working team: M.A. Martins-Louçâo,
F. Catarino and C. Cruz
Institut de Recerca i Tecnologia Agroalim Cultivar characterization
entàries (IRTA) and evaluation, germplasm
Departament d’Arboricultura Mediterrània collection, clonal selection,
Centre Mas Bové physiology of reproduction,
Apartat 415, 43280 Reus (Tarragona) vegetative propagation,
Tel: +34-77-343252. Fax: +34-77-344055 and gum (CBG) quality
Email: firstname.lastname@example.org orchard management
Germplasm bank (Reus and Tortosa)
Working team: J. Tous, I. Batlle, A. Romero,
J. Plana, M. Rovira and N. Aletà
Conselleria d’Agricultura del Govern Balear Cultivar collection (Finca
Pasaje Torrella 1 Experimental ‘Sa Granja’)
07012 Palma de Majorca
Tel. +34-71-176100. Fax: +34-71-176156
Curator: J. Rallo
Private farm: Cultivar collection
Partida ‘El Paraiso’ 40
03570 Villajoyosa (Alicante)
Curator: J. Lloret
Institut National de la Recherche Cultivar collection
Laboratoire d’Arboriculture Fruitière
Avenue de l’Indépendance
Tel: +216-1-231985. Fax: +216-1-752897
Curator: B. Jraidi
INEC (Institut Europeen des Industries
de la Gomme de Caroube)
Institut of Food Science
Department of Food Science
Swiss Federal Institute of Technology
Zürich, ETH Zentrum, LFO F18
8092 Zürich, Switzerland
Tel: +41-1-6325368. Fax: +41-1-2620994
General Secretary: Z. Puhan
Appendix III. Basic descriptor list for carob (Ceratonia
siliqua L.) cultivars
Characteristic† Category and rank
Sex male, female or hermaphrodite
Vigour very high, high, medium
Growth habit upright, open, weeping
Foliage density most dense, dense, less dense
Branching dense, intermediate, sparse
Rachis length (cm)
Number of leaflets
Leaflet shape elliptic, oval, round
Leaflet area (cm2) small ( ), medium ( ), big ( )
Length/width relation (L/W) short, long, narrow
Leaf colour light green, green, dark green
Length (cm) short (<8), medium (8-10), long (>10)
Flowers per inflorescence many (>30), medium (15-30), few
Colour green, yellow, red
Nodosity insertion yes, no
4 Fruit pod or bean
Shape straight, curved, twisting
Surface smooth, rough, very rough
Colour black, brown, reddish
Length (cm) short (<14), medium (14-18), long
Width (cm) small ( ), medium ( ), big ( )
Pod thickness thin ( ), medium ( ), thick ( )
Pedicel length short ( ), medium ( ), long ( )
Pod weight (g)
Number of seeds per pod
Seed yield (%) low (<9.5), medium (9.5-13), high
Sugar content (%) low (<40), medium (40-50), high (>50)
Fibre content (%)
5 Seed or kernel
Shape round, oval, elliptic
Surface smooth, rough, very rough
Colour red-brown, brown, black-brown
Length (L) (cm) short ( ), medium ( ), long ( )
Width (W) (cm) narrow ( ), medium ( ), wide ( )
Thickness (T) (cm) thin ( ), medium ( ), thick ( )
L/W, L/T, W/T relations
Volume of 100 seed (cc)
Seed weight (g, average 100 seeds) small (< 0.17), medium ( 0.17- 0.2),
Gum content (% dry wt. low (< 48), medium (48-2), high (>52)
Yield; regularity of production; precocity; sensitivity to frost, wind; pest and
disease susceptibility; ripening season; ease of harvesting, etc.
Uses of carob pods (animal feed or human food); tannin content; sugar, etc.;
quality of CBG (viscosity and gel strength); germ content, etc.
† Passport, management, and environmental and site descriptors are omitted.
Source: modified from Tous et al. (1996).