Turkish Journal of
2015, 20(1), 78-84
YIELD AND HERB QUALITY OF THYME (Thymus vulgaris L.)
DEPENDING ON HARVEST TIME
Beata KRÓL *1, Anna KIEŁTYKA-DADASIEWICZ2
1University of Life Sciences in Lublin, Department of Industrial and Medicinal Plants, POLAND,
2State Higher Vocational School in Krosno, POLAND
*Corresponding author: firstname.lastname@example.org
Thyme (Thymus vulgaris L) is a medical and aromatic plant intensively used in pharmaceutical, food, and
cosmetic industries. Our investigations carried out in 2010-2011 were focused on effect of harvest time on yield
and herb quality of two thyme cultivars (‘Słoneczko’ and ‘Deutscher Winter’). Plants were harvested in the
first year of cultivation in three periods: 140, 160, and 180 days after sowing (i.e. in the third decade of August,
second decade of September and first decade of October). The study showed that harvesting time had a
significant effect on the yield and quality of thyme. The delayed harvesting resulted in increased plant height
and their mass but decreased quality of herb (lesser quantity of essential oil and thymol). The optimal time of
harvest appeared to be 160 days after sowing (i.e. in the second decade of September. Harvest in this time
ensured fairly good yield of herb and high its quality. The weather conditions prevailing during the vegetation
period had a substantial effect on the yield and quality of herb. The ‘Deutscher Winter’ cultivar produced
higher yields in favourable weather conditions, whereas the ‘Słoneczko’ cultivar exhibited a more stable yield
in adverse atmospheric conditions.
Key words: cultivar, essential oil content, thymol, Thymus vulgaris
Thyme (Thymus vulgaris L.) is a perennial plant
belonging to the Lamiaceae family. It is native to Europe
and the Mediterranean basin and adaptable to a wide range
of environmental conditions (Stahl-Biskup and Sáez,
2002). Thyme is an aromatic medicinal plant of increasing
economic importance in Europe, Asia, North Africa and
North America. Essential oil of thyme has been reported
to be one of top 10 of essential oils (Maghdi and Maki,
The pharmacological properties of the plant and of its
different extracts, in particular the essential oils, has been
thoroughly studied and afforded the many industrial
mainly as food and cosmetic additive (Sacchetti et al.,
2005) and medical applications (Maghdi and Maki, 2003).
The oil was reported to have antimicrobial (bacteria and
fungi) (Cetin et al., 2011), expectorant (Büechi et al.,
2005) activities, most of which are mediated by thymol
and carvacrol. Antispasmodic (Begrow et al., 2010) as
well as antioxidant (Haraguchi et al., 1996) activities were
also reported for the alcoholic extract of the plant.
Thyme is cultivated in many regions of world and is
one of the most important medicinal plant in Europe.
Thyme plantations usually survive 2 or 3 year, but in some
regions, the plants may freeze during cold winters.
Therefore in countries, where the winters are severe
(Scandinavian countries, Eastern Europe and Canada)
thyme is treated as a one year culture (Dambrauskiene et
al., 1999; Letchamo et al., 1999; Galambosi et al., 2002).
The yield of herb of thyme can be influenced by
environmental factors, as well as by agricultural practice
(Stahl-Biskup and Sáez, 2002). Harvesting time is one of
the important factors determining the quantitative and
qualitative characteristics of thyme (Badi et al., 2004)
The essential oil content and its chemical composition
are the most important characteristics of aromatic herbs.
Content of essential oil in dry herb of thyme ranges from
0.3 % (Ozguven and Tansi, 1998) to 4.0 % (Carlen et al.,
2010). The content of the essential oil depends from
several factors, the most important being genetic
characteristics, stage of development (Christensen and
Grevsen, 2006; Mewes at al., 2008) environmental
conditions (Raal et al., 2005; Alizadeh et al., 2011).
Agronomic factors (Kołodziej, 2009; Król, 2009) as well
as drying and storage conditions (Calin-Sanchez et al.,
2013) exerts an influence on the essential oils content too.
There are however scarce information on the effect time
of harvest on the chemical composition of essential oil.
The aim of this study was to analyze the impact of
time of the harvest on the yield and quality of herb two
cultivars of thyme utilized as a one year plantation
MATERIAL AND METHODS
The study was carried out at the Experimental Farm of
the University of Life Sciences in Lublin (51° 14′ 53″ N,
22° 34′ 13″ E), Poland, during the 2010 and 2011 growing
seasons. The experiment was conducted on brown
podzolic soil of loess origin, neutral in reaction (pHKCl -
7.1), characterized by high content of phosphorus (85
mg∙P kg-1) and average potassium (166 mg K∙kg-1) and
magnesium (65 mg Mg∙kg-1) contents.
The study comprised two cultivars of thyme
('Słoneczko' and 'Deutscher Winter') and consisted of
three harvest times: H1 - 140 days after sowing (DAS) -
i.e. in the third decade of August; H2 - 160 DAS - i.e. in
the second decade of September; and H3 - 180 DAS - i.e.
in the first decade of October. The 'Słoneczko' cultivar
seeds were supplied by the Institute of Natural Fibres and
Medicinal Plants, Poland and the ‘Deutscher Winter’
cultivar by Bingenheimer Saatgut AG, Germany. The
study was conducted in a randomized block design with
four replications. Each experimental plot was 4 m long
and 2.5 m wide (10 m2). Seeds were sown directly into the
ground in the first decade of April in rows spaced 30 cm
(sowing rate 5 kg seeds ha-1). Mineral fertilizers were
applied in the amount of N - 60; P - 22; K - 100 kg per ha-
1 (phosphorus and potassium were applied as triple
superphosphate and potassium chloride before sowing the
seeds). Nitrogen fertilization was applied (in two doses -
half before sowing and half after plant emergence) as
ammonium nitrate. Manual weed control and soil
loosening in interrow spaces was performed during the
growth of plants.
Before harvest, plant height was determined (20 plants
measured from each object). After harvest, the herb was
weighed and dried (in a drying house at 35°C) and air-dry
mass was determined. Next, the herb was rubbed on sieves
(mesh diameter 5mm) and thus dry leaves yield was
The essential oil was extracted from air-dried leaves
(30 g) in a glass Clevenger-type distillation apparatus
following European Pharmacopoeia (2004) and subjecting
the material to hydrodistillation for 3 h. The assays were
conducted in triplicate. The extracted essential oil was
stored in a dark glass container at a temperature of – 10°C
until the time of chromatographic separation. The
quantitative and qualitative determination of the essential
oil components was made using a gas chromatograph
(Varian 4000 GC/MS/MS) equipped with a FID detector
and fused silica capillary column (25 m x 0.2 mm). The
carrier gas was helium with the splitting ratio of 1:1000
and capillary flow rate of 0.5 ml min-1. A temperature of
50°C was applied for 1 min, and then the temperature was
incremented to 250°C at a rate of 4°C min–1; 250°C was
applied for 10 min. The qualitative analysis was carried
out on the basis of MS spectra, which were compared with
the spectra in the NIST Mass Spectral Library (NIST
2002) and with data available in the literature (Joulain and
König, 1998; Adams 2001). The identity of the
compounds was confirmed by their retention indices,
taken from the literature (Joulain and König, 1998; Adams
The predicted production yields of thyme oils, in litres
per hectare, were calculated from the dry leaves yield and
the oil content. The numerical results of the experiment
were statistically elaborated by the analysis of variance
(ANOVA) for three factors - harvest time H (3), cultivars
C (2) and years Y (2). The least significant difference test
was used to compare differences in means among
treatments at the 0.05 probability level.
The basic climatic factors during thyme vegetation are
presented in Table 1. In order to determine the variability
of meteorological factors and assess their effect on the
yield and quality of the plant, the Sielianinov
hydrothermal coefficient (k) was calculated based on the
equation: k = P/0.1∑ t
P – total rainfall in the given period (mm)
Σ t – total of average daily air temperatures from that
period (ºC) (Skowera and Puła, 2004).
According to the classification presented by Skowera
and Puła (2004), there are distinguished the following
conditions: extremely dry (k ≤ 0.4), very dry (k ≤ 0.7), dry
(k ≤ 1.0), rather dry (k ≤ 1.3), optimal (k ≤ 1.6), rather wet
(k ≤ 2.0), wet (k ≤ 2.5), very wet (k ≤ 3.0), and extremely
wet (k >3.0).
Thermal conditions in both years of the field
experiment were favourable for thyme; the average air
temperature in the vegetation season was markedly higher
if compared with that in the long-term period. Moisture
conditions were also more favourable than in the long-
term period. In terms of precipitation, 2010 was more
advantageous, not only because of greater amounts but
also more uniform distribution of rainfall. In 2011,
symptoms of drought (in May) and severe drought (in
August and September) occurred as a result of irregular
Table 1. Rainfall, air temperature and hydrothermal coefficient during vegetation of thyme in 2010 and 2011 in comparison with
multi-year period (1980-2009)
Average temperature of air (oC)
Monthly of rainfall (mm)
Sielianinov’s hydrothermal coefficient
Source: Laboratory of Agrometeorology, University of Life Sciences in Lublin, Poland
RESULTS AND DISCUSSION
The height of plants oscillated between 23.4 and 32.8
cm and markedly depended on both: harvesting time and
weather conditions during vegetation (Table 2). The plants
were higher in 2010, when the rainfall was greater and
more uniformly distributed than in 2011. (Table 1, 2). At
the consecutive harvests the height of plants increased (the
significant differences however were only between the
first and third harvest). The height of thyme plants varies
to a great extent and depends on the genotype (Mewes at
al., 2008), environmental conditions (Galambosi et al.,
2002) and cultivation practice (Badi et al., 2004) and
oscillates between 10 and 50 cm.
Table 2. The influence of harvest time on height of plants of thyme (cm)
Mean for harvest time
LSD0.05 harvest time (H) - 2.53; cultivar (C) - ns.; years (Y) - 4.25; H x C – ns.; C x Y - 3.71; H x Y - 3.34
ns. - no significant differences
*H1 – 140 days after sowing
H2 – 160 days after sowing
H3 – 180 days after sowing
The herb yield depended significantly on the factors
studied (Table 3). In both cultivars, the highest yields of
fresh and air-dry herb were achieved from plants
harvested in the first decade of October (i.e. 180 DAS),
while the lowest – during the first harvest (140 DAS). No
significant differences were found in the fresh and air dry
herb yields between the cultivars, however, the
‘Słoneczko’ yields were more stable in adverse weather
conditions in 2011 year when there were symptoms of
drought (Table 3). Chauhan et al. (2011) in diverse
climatical conditions the highest yields of fresh and dry
mass of herb obtained when thyme was harvested 115
days after sowing. The latest harvesting (180 DAS) caused
decreased fresh and dry herb weight, which resulted from
stem drying and defoliation. Rey (1991) considers harvest
time of thyme as an important factor affecting yields and
their quality. He asserts, that optimal time may differ
markedly between particular regions.
Table 3. The influence of harvest time of thyme on yield of fresh and air dry herb and ratio fresh to air dry herb
Yield of fresh herb
Yield of air dry herb
air dry herb
Mean for harvest time
harvest time (H)
H x C
C x Y
H x Y
ns. - no significant differences
*See table 2
The ratio of the fresh to dry herb weight in our
experiment ranged from 2.39 to 3.51 (Table 3). A high
value of this trait is disadvantageous, as this involves
higher costs of drying. The delay in harvesting thyme
decreased water content in the herb, which resulted in a
decline in the proportion between the fresh and air-dry
weight of the herb (Table 3). According to literature data,
the ratio of fresh to dry herb weight in thyme grown in
Poland is 2.4 - 3.5 (Kołodziej 2009; Król, 2009). Similar
value of this feature (2.6 – 3.7) was reported in
experiments conducted in diverse climatic conditions
(Badi et al., 2004).
In our experiment, the dry leaves yields ranged
between 2.23 and 4.08 t∙ha-1, and corresponded with
results obtained by other authors in Poland (Table 4)
(Kołodziej, 2009; Król, 2009). Similar results were
obtained in Finland whereas in Canada thyme yields were
lower and did not exceed 1.5 t∙ha-1 (Letchamo et al.,
1999). Stahl-Biskup and Sáez (2002) report that yields of
thyme in the first year of vegetation amount from 2 to 2.5
t∙ha-1, of dry plant material. Investigations conducted by
Dudaš and Böhme (2004) showed that the ‘Deutscher
Winter’ gave higher yield than the ‘Słoneczko’, which in
turn was characterised by a better proportion of leaves. In
our experiment, there were no differences in the mean
yields of dry leaves between these cultivars, but an
interaction between the cultivars and years was reported.
‘Deutscher Winter’ produced higher yields in favourable
weather conditions (2010), whereas in unfavourable
weather (2011), yields were significantly reduced (by
32%). Also Galambosi et al. (2002) reported strong
susceptibility of this cultivar to adverse atmospheric
conditions (decrease of yields by 15-35 %).
Table 4. Yield of dry leaves and contribution of leaves in herb of thyme
Yield of dry leaves
Contribution of leaves
Mean for harvest time
harvest time (H) - 0.41; cultivar (C) - n.s; year (Y) - 0.73
H x C - 0.70; C x Y - 0.84; H x Y - 0.65
* See table 2
Both cultivars produced the lowest yield of dry leaves
in the objects with the earliest harvest (140 DAS),
delaying harvest resulted in significant increase of yield
An important indication of the quality herb of thyme is
the percentage of leaves, as the essential oil is
accumulated in oil glandules present in these organs but
scarce in the stems (they are discarded in the final stage
of raw material preparation) (Sharafzadeh et al., 2010).
Słoneczko’ cultivar is characterised by the highest
amounts of leaves among the European varieties of thyme
(Dudaš and Böhme, 2004). Similarly, in our research the
‘Słoneczko’ cultivar contained greater amounts of leaves
(43.2% versus 40.8% in the ‘Deutscher Winter’ cultivar)
(Table 4). The share of leaves in air-dry weight was also
related to weather conditions and time of harvest. In both
cultivars, the highest share of leaves was noted in herb
from the first harvest (140 DAS) and the lowest - at the
last harvest (180 DAS- Table 4). This was probably
caused by defoliation and lignification of stems. However
in experiment of Rey (1991) in different climatical
conditions the delay in harvesting thyme increased share
In our study, the content of essential oil in the dry
leaves ranged from 2.23 to 3.61% (Table 5) and was
comparable with results of Galambosi et al. (2002),
Zawiślak (2007), Marzec et al. (2010) but higher than
stated by Badi et al. (2004), Alizadeh et al. (2011) and
Christensen and Grevsen (2006). The content of essential
oil in thyme plants can be markedly affected by
environmental conditions, time of harvest and other
agronomical factors (Stahl-Biskup and Sáez, 2002; Raal et
al., 2005). In our study, the content of essential oil in the
dry leaves of both cultivars was largely determined by the
harvest date and weather conditions during the vegetation
season (both cultivars responded similarly - Table 5). The
herb was harvested at the first date contained the greatest
quantity of essential oil (mean 3.44%) whereas the
smallest - at the third date (2.67%). The differences
between the first and second harvest were negligible while
between second and third – considerable. Decreasing
content of essential oil accompanying delayed thyme
harvest was reported by Badi et al. (2004) and Rey (1991).
Also Christensen and Grevsen (2006), obtained more
essential oil in thyme herb harvested in September than in
October. Galambosi et al. (2002) however report that
shorter growing season affects first at all biomass
production, and has only slight influence on essential oil
content and composition.
Table 5. The effect of harvest time of thyme on the content and yield of essential oil; percent of thymol in oil
Essential oil content
Yield of essential oil
Mean for harvest time
harvest time (H)
H x C
C x Y
H x Y
* See table 2
ns - no significant differences
In our experiment the mean content of essential oil in
both cultivars did not differ markedly (Table 5). In study
carried out by Dudaš and Böhme (2004) where there were
compared several European cultivars, herb of ‘Deutscher
Winter’ contained more essential oil in comparison with
'Słoneczko’. Seidler-Łożykowska (2007) reported that
atmospheric conditions prevailing during the growing
season were an important factor determining essential oil
content in thyme. In our study, both the herb yield and oil
content were higher in 2010, which was characterised by
higher precipitation rates and lower temperatures during
the growing season, than those in 2011 (Table 4, 5).
Berbeć and Kołodziej (2007) found that appropriate water
supply ensured high yields but also contributed to
reduction of the quantity of active compounds in herb, in
our experiment however this opinion was not confirmed.
In our experiment, the oil yield (a resultant of dry leaf
yield and essential oil content) was the highest
(irrespective of the cultivar) in objects where the plants
were harvested 160 days after seed sowing (Table 5). The
mean essential oil yields (regardless of the years and
harvesting periods) in both cultivars did not differ
significantly. Comparison of the essential oil yields in
relation to the year of study revealed greater variation in
the ‘Deutscher Winter’ cultivar, which strongly reacted to
the water deficiency in August and September 2011 by a
substantial decline in the essential oil yield. In turn, at the
favourable precipitation distribution in 2010, this cultivar
gave higher yields of essential oil than the ‘Słoneczko’
cultivar (Table 5).
Content of thymol in essential oil is considered to be
one of important factors of thyme quality (Stahl-Biskup
and Sáez, 2002). In our study this content ranged from
49.9% to 59.2% and was comparable with that determined
by Zawiślak (2007), Galambosi et al. 2002, and Marzec et
al. (2010). Asllani and Toska (2003) found it at the lower
level (23.1%-50.1%) in Albanian thyme, Horváth et al.
(2006) in herbs from Hungary (40,5%) and Badi et al.
(2004) in essential oil from thyme grown in Iran (36% -
45%). The chemical composition of thyme’s essential oil
depends upon several factors, such as environment of
growing (Galambosi et al. 2002), development stage
(Hudaib et al., 2002) and chemotypes (Thompson et al.,
2003). In our study, the content of thymol in the essential
oil was dependent on the harvest date and cultivars (Table
5). The highest level of thymol was recorded in herb
harvested in the third decade of August, (i.e. 140 days
after sowing), and succeeding harvests brought about
decrease its content. The similar dependence observed
Chauhan et al. (2011), and Hudaib et al. (2002). Senatore
(1996) who investigated the essential oil of a wild Italian
thyme, Thymus pulegioides L., the highest content of
thymol found in herb gathered in May (39.1%) and much
smaller in September (20.8%). This does not correspond
however with the experiment of Christensen and Grevsen
(2006) who found more thymol in herb cultivated thyme
harvested in October in comparison with that harvested in
September. In our experiment markedly more thymol
conatined herb of ‘Słoneczko’ cultivar in comparison with
‘Deuscher Winter’ (Table 5). Also Dudaš and Böhme
(2004), reported that ‘Słoneczko’ characterized the highest
amounts of thymol in essential oil among compared
Examined in the experiment harvest dates of the thyme
(140, 160, and 180 days after sowing) had a significant
effect on the herb yield and its quality. Along with
delaying harvest, yield increased while quality of herb
decreased. The highest yield of herb was recorded at latest
date of harvest (180 days after sowing), the herb however
characterized low quality, contained smaller quantity of
essential oil and lesser amount of valuable thymol. The
optimal harvest time of both cultivars compared
(‘Słoneczko’ and ‘Deutscher Winter’) proved to be 160
days after sowing (mid of September), when fairly good
yields were accompanied by reasonable quality of herb.
The weather conditions during the vegetation period had a
significant effect on the herb yield and a minor impact on
the its quality. Higher yields of herb was recorded in 2010
year which characterized abound and uniformly
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