Pollen analyses of honey from Finland

Abstract

The present study reports results of qualitative melissopalynological analyses of Finnish honey between the years 2000-2007 and changes in its pollen content from the period 1960-2007. Altogether the pollen content of 734 honey samples was analysed with an average of 415 pollen grains counted from a sample. Pollen of Trifolium repens type, Rubus spp., Salix spp. and the Brassicaceae family were present in more than 90% of the samples, and these pollen types were also found in the highest proportions. Annual variation in the relative amounts of the most numerous pollen types could be as high as 10%. On the basis of the pollen spectra of the honey samples, four regions of forage plants for bees could be identified in Finland. In the period between 1960 and 2007, the most marked change observed was that the percentage of the Trifolium spp. pollen type had decreased from 70% to 10%, while the proportions of Brassicaceae and Rosaceae pollen types showed a corresponding increase.

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Pollen analyses of honey from Finland
Anneli Salonen
a
; Tarja Ollikka
b
; Elisabeth Grönlund
c
; Lauri Ruottinen
bd
; Riitta Julkunen-Tiitto
a
a
Natural Product Research Laboratories, Faculty of Biosciences, University of Joensuu, Finland
b
Finnish Beekeepers Association, Helsinki, Finland
c
Ecological Research Institute, Faculty of
Biosciences, University of Joensuu, Finland
d
MTT Agrifood Research, Helsinki, Finland
Online publication date: 07 December 2009
To cite this Article Salonen, Anneli, Ollikka, Tarja, Grönlund, Elisabeth, Ruottinen, Lauri and Julkunen-Tiitto, Riitta(2009)
'Pollen analyses of honey from Finland', Grana, 48: 4, 281 — 289
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ISSN 0017-3134 print/ISSN 1651-2049 online © 2009 Collegium Palynologicum Scandinavicum
DOI: 10.1080/00173130903363550
Grana, 2009; 48: 281–289
SGRA
Pollen analyses of honey from Finland
Pollen analyses of honey from Finland
ANNELI SALONEN
1
, TARJA OLLIKKA
2
, ELISABETH GRÖNLUND
4
,
LAURI RUOTTINEN
2,3
& RIITTA JULKUNEN-TIITTO
1
1
Natural Product Research Laboratories, Faculty of Biosciences, University of Joensuu, Finland,
2
Finnish Beekeepers
Association, Helsinki, Finland,
3
MTT Agrifood Research, Helsinki, Finland,
4
Ecological Research Institute,
Faculty of Biosciences, University of Joensuu, Finland
Abstract
The present study reports results of qualitative melissopalynological analyses of Finnish honey between the years 2000–2007
and changes in its pollen content from the period 1960–2007. Altogether the pollen content of 734 honey samples was
analysed with an average of 415 pollen grains counted from a sample. Pollen of Trifolium repens type, Rubus spp., Salix spp.
and the Brassicaceae family were present in more than 90% of the samples, and these pollen types were also found in the
highest proportions. Annual variation in the relative amounts of the most numerous pollen types could be as high as 10%.
On the basis of the pollen spectra of the honey samples, four regions of forage plants for bees could be identified in Finland.
In the period between 1960 and 2007, the most marked change observed was that the percentage of the Trifolium spp.
pollen type had decreased from 70% to 10%, while the proportions of Brassicaceae and Rosaceae pollen types showed a
corresponding increase.
Keywords: Pollen analysis, melissopalynology, bee plants
Pollen grains are always found in natural honey
processed by standardised methods. The pollen con-
tent of the honey not only reflects regional agricul-
tural practices and forest vegetation, but also the
floral diversity and species composition of the plants
foraged by the honey bees and, as such, the mellifer-
ous plant species available in the vicinity of the apiary
(Louveaux et al., 1978). Honey bees select their for-
age plants primarily on the basis of the sugar content
of the plant nectar, the raw material of honey
(Crane, 1980). Pollen grains are usually present in
floral nectar and thus are considered to be the prim-
ary source of pollen in honey. Moreover, exogenous
pollen may be introduced into a beehive in numer-
ous ways: bees carry pollen to the hive in their pollen
baskets, pollen grains may fall from bees’ body parts
into the nectar-filled combs, airborne pollen may
enter the hive via air currents, used wax combs are
added to hives, or imported pollen is fed to bees.
There are around 2000 beekeepers in Finland
maintaining about 50000 bee colonies; total honey
yield ranges from 1 to 3 million kilos annually. On
an average, one colony produces 26–56 kg of honey
per annum (Anonymous, 2008). The northernmost
bee colonies in Finland are found in Inari (69º N),
but more than 65% of the honey is produced in the
southern and western parts of the country (Regions 9,
10, and 13–19 in Figure 1), where cultivated
Brassicaceae species are the main honeybee plants.
Finland is situated on the boreal coniferous zone
of Scandinavia. Phytogeographic regions of Finland
are hemi-, southern-, middle- and northern boreal
zones and predominant forest types range from
mesic nutrient-rich to oligotrophic dry heath conif-
erous forests (Ahti et al., 1968). In the eastern and
northern Finland the main honey yield comes from
wild forest plants. The pollen types of wild growing
plants are derived from typical boreal coniferous
Correspondence: Anneli Salonen, Natural Product Research Laboratories, Faculty of Biosciences, University of Joensuu, P.O. Box 111, FI-80101 Joensuu,
Finland. E-mail: anneli.salonen@cc.joensuu.fi
(Received 17 February 2009; accepted 12 August 2009)
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282 A. Salonen et al.
zone flora. These species are, for example, Salix spp.,
Epilobium angustifolium L., Calluna vulgaris (L.) J.
Hull, Menyanthes trifoliata L., Anthyllis vulneraria L.,
Knautia arvensis (L.) T. Coulter, Tussilago farfara L.,
Astragalus spp., Trifolium spp., Rhamnaceae spp.
and Geranium spp. as well as wild berries Rubus
idaeus L., R. chamaemorus L., R. arcticus L., Fragaria
vesca Coville, Vaccinium myrtillis L., V. vitis-idaea L.,
V. uliginosum L. and V. oxycoccos L.
To date, melissopalynological studies in the Euro-
pean boreal coniferous zone have been conducted
only in Finland. Results of honey pollen analyses are
available from as early as 1937 and 1960 (Martimo,
1945 and Aarnio, 1961, respectively). These studies
indicated that the proportion of Trifolium repens type
pollen was about 50%. Later studies by Varis et al.
(1982), consisting of 120 honey samples from 1977–
1978, revealed a marked shift in the main forage
plants, as Brassicaceae pollen became the dominant
type in the total pollen content of honey. Moreover,
Varis (2000) found that in 1997 the proportion of
Brassicaceae pollen had increased to 60%, accompa-
nied by a simultaneous decrease in the Trifolium type
species. The most likely explanation for this is that
the cultivation area of the oil-plant species of the
Brassicaceae family (Brassica rapa ssp. oleifera and B.
napus ssp. oleifera) has steadily increased in Finland
since the 1970s (Anonymous, 2008).
Systematic annual pollen analyses were started by
the Finnish Beekeepers Association in 1995 with the
aim of observing the quality of the honey sold in
Finland, and the qualitative pollen content of
approximately 100 samples are analysed annually.
The aim of the present study is to report the
results of qualitative pollen analyses from 734 honey
samples collected in Finland during 2000–2007.
The main focus is in the floristic spectrum of plants
foraged by honey bees and in the identification of
the most important plant sources for honey pollen.
Also considered are the geographical variability of
forage plants in Finland and changes in the forage
plant composition between 1960 and 2007.
Material and methods
Honey samples were collected by the Finnish Beekeep-
ers Association from different honey selling enterprises
in Finland or assigned for quality control analyses by
beekeepers during 2000–2007. Honey samples came
from different hives and different locations each year
and the samples were purchased or received during
autumn and winter. Most Finnish beekeepers collect
honey from their colonies only once a year, therefore
these honey samples present more or less the whole
yield of one year. The geographical origins of the
honey samples are shown in Table I and Figure 1.
There were no honey samples from the Aland Islands.
Qualitative melissopalynological analyses were
conducted by slightly modified methods recom-
mended by the International Commission for Bee
Botany (Louveaux et al., 1978). The honey samples
for microscopic pollen analysis were prepared in the
laboratory as follows: ten grams of honey were dis-
solved in 20 ml of distilled water and centrifuged
(10 minutes, 3500 r/min). The supernatant was dis-
posed of and the residue washed again with 20 ml of
water. The supernatant was again removed after the
second centrifugation (5 min, 3500 r/min) and the
residue transferred using a Pasteur pipette onto a
microscope slide, which was left to dry, covered by a
piece of paper, until the next day. The sample area
was subsequently covered with Kaiser’s glycerol
gelatine and a cover slip, and again left to dry under
paper for 24 hours.
Figure 1. The forage plants regions (Region I–IV) and the
administrative regions (with numbers) – referring to Table I.
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Pollen analyses of honey from Finland 283
Pollen identification was conducted according to
pollen types described in Table II. Juniperus type
includes Juniperus spp. and Taxus spp., Picea type
includes Picea spp. and Abies spp. Pollen type Aster-
aceae/Liguliflorae includes taxa Achillea spp. and
Leucanthemum spp., and Asteraceae/Tubuliflorae
type includes Aster spp., Senecio spp., Erogeron spp.
and Solidago spp. Cirsium type includes Cirsium spp.
and Carduus spp., where as Malus type includes
Malus spp. and Pyrus spp. Nymphaea type includes
Nymphaea spp. and Nuphar spp. Syringa type
includes Syringa spp. and Ligustrum spp. and Tarax-
acum type includes Taraxacum spp. and Sonchus spp.
Trifolium pratense type includes Trifolium pratense L.,
T. medium L., and T. incarnatum L. Trifolium repens
type includes T. repens L., T. resupinatum L., and
other T. hybridum L., but not Trifolium hybridum
‘Frida’ L., which can be distinguished from other
Trifolium species. Vicia type includes Vicia spp.,
Lathyrus spp., and Pisum spp.
If bees use honey dew as the raw material of
honey, honey dew elements like fungal spores,
hyphae and microscopic algae may occur in honey.
The amount of honey dew elements was also
counted, if they were observed in the honey samples.
Frequency of occurrence denotes the relative
amount (%) of samples in which a certain pollen
type was encountered. It was calculated by dividing
the number of samples in which a pollen type
occurred by the total number of samples and then
multiplying the quotient by 100. For the counting of
the relative proportion of a pollen type we formed a
huge honey sample by summarising the calculations
of each pollen type from one year. Then the relative
proportion was calculated by dividing the sum of
one pollen type by the total number of all counted
pollen grains in that year and then multiplying the
quotient by 100.
In order to find out the variability of the plants
foraged by bees in provinces of Finland, all the
honey samples were classified according to their
respective geographical origin. The numbers of each
pollen type of one geographical area were summa-
rised and the relative proportion of a pollen type was
calculated as described above.
The percentage distribution of the most com-
mon pollen types in Finnish honey samples from
the years 1960, 1962, 1963, 1977 and 1978 was
compared by Varis et al. (1982) (Figure 5). The
corresponding pollen data of the present study
(from the years 2000 earliest, 2003 middle, and
2007 latest) were added to the data set of Varis
et al. (1982). The pollen types for the comparison
were the same as those used in 1982 by Varis:
Brassicaceae, Rosaceae (including Fragaria spp.,
Rubus chamaemorus, Rubus spp. and Sorbus spp.),
Apiaceae, Trifolium repens type, Filipendula spp.,
Asteraceae (including Asteraceae/Liguliflorae,
Table I. Administrative regions of Finland (number refers to Figure 1) and the number of honey samples obtained for the pollen analyses
of the present study. Regions grouped to forage plant regions (I – IV; in bold), as in Figure 4.
Forage region/Administrative regions 2000 2001 2002 2003 2004 2005 2006 2007 Total
Region I 91
1. Lapland 1 4 1 3 1 10
2. Northern Ostrobothnia 926317432
3. Kainuu 21 11 5
4. North Karelia 4 643727538
11. Central Ostrobothnia 1 1 1 3 6
Region II 157
5. Northern Savonia 2 2393104740
6. Southern Savonia 8 81141252757
8. Ostrobothnia 2 1 4 5 1 13
12. Central Finland 311212376347
Region III 217
9. Pirkanmaa 1 4 6 10 11 8 7 12 59
10. Satakunta 1 443311421
14. South Karelia 2 721534125
15. Päijänne Tavastia 4 036363328
16. Tavastia Proper 316725571156
19. Kymenlaakso 631266428
Region IV 269
7. Southern Ostrobothnia 1 1 6 2 2 6 18
13. Southwest Finland 9 13 16 9 17 11 7 16 98
17. Uusimaa 13 19 8 4 8 20 11 12 95
18. Eastern Uusimaa 815155951 58
Total 60 127 88 85 95 97 83 99 734
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284 A. Salonen et al.
Asteraceae/Tubuliflorae, Tussilago farfara, Cirsium
spp., Carduus spp., Centaurea cyanus L., C. jacea
L., C. montana L., Taraxacum spp. and Sonchus
spp.) and a seventh pollen type for the others.
Results
A total of 734 honey samples were analysed from
the years 2000–2007. All observed melliferous
and non-melliferous pollen grains and honey dew
elements were counted. An average of 415 pollen
grains were counted from the samples (Table III).
Altogether, 116 different pollen types were ana-
lysed from the honey samples. A pollen type may
represent a family, a genus or a species. Alto-
gether, 23 types were identified to species level,
78 to genus level and 15 to family level (Table II),
9–47 of which could be found in one honey sam-
ple (Table III). On average, the samples con-
tained 27.3 pollen types, 21.1 of which originated
from melliferous and 6.3 from non-melliferous
plant sources (Table III). Unidentified pollen taxa
occurred only in five samples.
Honeydew honey is not collected by bees in
Finland every year. Thus honeydew elements were
found in only 28 honey samples, from the years
2000, 2002, 2003, 2006 and 2007.
Frequency of occurrence of the pollen types
Trifolium repens type, Rubus spp., Salix spp., Brassi-
caceae and Apiaceae pollen types were encountered
in more than 90% of the honey samples (Figure 2).
Commonly occurring types (> 75% frequency) were
also those of Trifolium pratense type, Vaccinium spp.,
Taraxcum type, Epilobium spp. and Trifolium hybri-
dum ‘Frida’. Pollen of Hieracium spp., Knautia
arvensis, Rubus arcticus, R. chamaemorus, Tussilago
farfara and Sedum spp. were found in less than 10%
of the samples, although these are relatively com-
mon plants in Finland.
Among the non-melliferous plants, Filipendula
spp. and Poaceae pollen types were present with the
highest frequencies (92% and 87%, respectively,
Figure 3). Wind pollinated pollen of Betula spp. and
Pinus spp. were quite commonly found in honey sam-
ples (45% and 44%, respectively; Figure 3). Pollen of
Clematis spp., Fraxinus spp. and Juglans spp. types
were not found in the honey samples during the
years 2000–2007.
Table II. The analysed pollen grains were classified into 116 pollen types, 88 of which are from melliferous plants and 28 from
non-melliferous plants (marked with an asterisk).
Pollen type Pollen type Pollen type Pollen type
Gymnosperm Chenopodium spp.* Linum spp. Ribes spp.
Juniperus type* Cirsium type Lonicera spp. Robinia pseudoacacia
Picea type* Citrullus spp. Lotus corniculatus Rosa spp.*
Pinus spp.* Clematis spp. Lupinus spp.* Rubus arcticus
Convolvulus arvensis Lythrum salicaria Rubus chamaemorus
Angiosperm Cornus spp . Malus type Rubus spp.
Acacia spp. Corylus avellana* Malvaceae Rumex spp.*
Acer spp.Crataegus spp. Medicago spp. Salix spp.
Aesculus spp. Cynoglossum sp. Melampyrum spp. Sambucus sp.*
Allium spp. Cyperaceae * Melilotus spp. Scrophulariaceae
Alnus spp.* Echium vulgare Menyanthes trifoliata Sedum ssp.
Anemone spp.* Epilobium spp. Myosotis spp. Solanum spp.
Anthyllis vulneraria Eucryphia sp. Myrtaceae Sorbus spp.
Apiaceae Fagopyrum esculentum Nymphaea type Symphytum spp.
Arctium spp. Fagus spp.* Onobrychis viciifolia Syringa type
Artemisia spp.*
Filipendula spp.* Oxalis spp. Taraxacum type
Asteraceae/Liguliflorae Fragaria spp. Papaver spp.* Tilia spp.
Asteraceae/Tubuliflorae Fraxinus spp.* Parthenocissus spp. Trifolium hybridum ‘Frida’
Astragalus spp.Galium spp. Phacelia spp. Trifolium pratense type
Betula spp.* Geranium spp. Phlox spp. Trifolium repens type
Borago officinalis Geum spp. Plantago spp.* Tussilago farfara
Brassicaceae Helianthus spp. Poaceae * Urtica spp.*
Calendula officinalis Hieracium spp. Polemonium spp. Vaccinium spp.
Calluna vulgaris Hypericum spp. Polygonum spp. Valeriana spp.
Campanulaceae Impatiens spp. Populus spp.* Veronica spp.
Caryophyllaceae Juglans spp.* Potentilla spp. Viburnum spp.
Castanea sativa Juncus spp.* Prunus spp. Viola spp.
Centaurea cyanus Knautia arvensis Quercus spp.* Vicia type
Centaurea jacea Lamiaceae Ranunculaceae Zea mays*
Centaurea montana Liliaceae Rhamnaceae
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Pollen analyses of honey from Finland 285
Relative proportions of pollen types
Of all the counted pollen grains, 75%–85%
belonged to the four most numerous melliferous
pollen types (Brassicaceae, Rubus spp., Trifolium
repens type and Salix spp.) (Table IV). Other pollen
types with a proportion higher than 2% were Apiaceae,
Fragaria spp., Menyanthes trifoliate, Myosotis spp., Sor-
bus spp., Trifolium hybridum ‘Frida’, Trifolium pratense
spp. and Vaccinium spp. (Table IV). About 95% of all
the counted pollen grains of melliferous plants
belonged to the 12 most numerous pollen types, and
only less than 5% of the pollen grains were repre-
sented by the 76 remaining types. The yearly varia-
tion of the relative proportion of a pollen type was
approximately 10%.
Of the non-melliferous plants, the Filipendula spp.
pollen type was the most common, representing
62.3% of all the non-melliferous pollen grains in the
data (Table IV). The relative proportions of Anemone
spp., Ranunculaceae and Rumex spp. pollen types
show a marked variation between different years. The
Ranunculaceae pollen variation was 4.2% – 12.9% in
the data set (calculated from Table IV). The annual
range of windborne Poaceae pollen type percentages
fluctuated between 6.8% – 15.4% (Table IV).
Table III. Total number of pollen grains counted, average number of pollen grains per sample, number of samples and average number o
f
melliferous and non-melliferous pollen types in samples per year (S.D. – standard deviation).
Year
Number of
honey
samples
Total number of
counted pollen
grains per year
Mean number of
counted pollen
grains per sample
Number of
melliferous taxa
Number of
non-melliferous taxa Total
Mean Range S.D. Mean Range S.D. Mean Range S.D.
2000 60 24873 414.6 21.0 12–33 4.7 7.2 3–14 2.80 27.0 17–42 8.1
2001 127 53810 423.7 18.9 8–35 5.1 5.7 2–12 2.2 24.6 10–47 6.4
2002 88 37466 425.8 23.8 11–35 5.7 7.6 2–14 2.2 31.3 19–46 6.9
2003 85 35211 414.2 21.9 10–37 5.6 6.8 3–12 2.2 29.0 16–46 6.9
2004 95 39173 412.3 21.4 11–31 5.0 5.7 2–11 1.9 27.1 15–40 6.2
2005 97 40241 414.9 20.7 7–32 5.5 5.8 1–10 2.0 26.5 12–40 6.8
2006 83 34275 413.0 18.5 7–30 4.7 5.6 1–14 2.4 24.1 9–40 6.1
2007 99 39807 402.1 22.7 9–41 6.9 6.3 1–15 2.5 29.0 13–50 8.8
734 309740 415.3 21.1 8–37 5.4 6.3 1–15 2.3 27.3 9–47 7.0
Figure 2. Frequency of occurrence of melliferous pollen types (> 30% frequency) in the years 2000–2007.
Trifolium repens type
Rubus spp.
Salix spp.
Brassicaceae
Apiaceae
Trifolium pratense type
Vaccinium spp.
Taraxacum type
Epilobium spp.
Fragaria spp.
Vicia type
Cirsium spp.
Sorbus spp.
Syringa type
Myosotis spp.
Asteraceae T
Malus type
Acer spp.
Hypericum spp.
Asteraceae L
Phacelia spp.
Prunus spp.
Geum spp.
Centaurea cyanus
0 10 20 30 40 50 60 70 80 90 100%
Rhamnaceae
Trifolium hybridum ‘Frida’
Figure 3. Frequency of occurrence of non-melliferous pollen
types (> 30% frequency) in the years 2000–2007.
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286 A. Salonen et al.
Geographical variation of bees’ forage plants in Finland
In order to find out the variability of the plants for-
aged by bees in different parts of Finland, the honey
samples were classified according to their geographi-
cal origin. The seven pollen types included in the
pollen type spectra were those that were either the
most numerous in the samples (Brassicaceae, Rubus
spp., Salix spp. and Trifolium spp.) or are considered
important plants as a unifloral honey source (Epilo-
bium spp. and Vaccinium spp.). According to the
similarity of the pollen type spectra, four source
regions of supply (Regions I – IV) could be outlined
with reference to the plants foraged by the bees
(Figure 4 and Table I).
The honey originating from Region I had low quan-
tities of Brassicaceae pollen type while Salix spp.,
Rubus spp. and Trifolium spp. occurred in high percent-
ages, and the proportion of Epilobium spp. pollen type
was higher than in other regions. Honey from Region
II was characterised by very high values (41% – 56%)
of the Rubus spp. pollen type. Rubus spp. and Brassi-
caceae pollen types occur in more or less equal propor-
tions in Region III, where the Trifolium spp. pollen type
was also abundant. In Region IV, Brassicaceae pollen
was by far the most common type (42% – 54%).
In the northern part of Finland (Lappi and
Kainuu), the proportion of Salix spp. pollen type
was relative high (27% – 31%), and here the propor-
tions of other wild plant pollen (e.g. Vaccinium spp.)
were also higher than in the other regions. The pro-
portion of the Trifolium spp. pollen type was highest
in Northern Ostrobothnia (31%).
Changes in the forage plants of bees since 1961
The change in the pollen spectrum of the most com-
mon pollen types in Finnish honey samples from the
years 1960, 1962, 1963, 1977 and 1978 was com-
pared by Varis et al. (1982). They found that the
proportion of Trifolium spp. pollen had decreased
(from 60% to 7%) in parallel with the increase in the
proportion of Brassicaceae pollen (from 3% to
20%). Furthermore, proportions of Rosaceae, Filipen-
dula spp. and Apiaceae pollen grains showed slight
rising tendencies. In this study, the corresponding
pollen data (from the years 2000, 2003, 2007) were
added to the data set of Varis et al. (1982) (Figure 5).
The results indicate that the proportion of Trifolium
spp. pollen type has decreased markedly, from 70%
to 13%, during the last five decades and has been
Table IV. Relative pollen values from melliferous and non-melliferous pollen types (types with participation greater than 2%).
Pollen type 2000 2001 2002 2003 2004 2005 2006 2007
Proportion of
total amount
of pollen grains
Melliferous
Apiaceae 1.46 1.92 1.33 1.60 11.22 2.71 1.22 3.39 3.19
Brassicaceae 35.91 34.60 26.81 29.29 41.12 31.77 24.59 31.28 32.04
F
ragaria spp. 0.78 2.04 1.06 0.98 1.13 0.89 0.79 1.25 1.18
M
enyanthes trifoliata 2.02 0.06 0.00 0.26 0.03 0.00 0.04 0.01 0.21
M
yosotis spp. 0.00 0.63 2.22 2.77 0.23 0.66 6.19 1.61 1.73
Rubus spp. 30.99 29.46 32.65 28.00 18.20 32.22 38.88 28.04 29.60
Salix spp. 8.48 4.59 12.50 7.73 6.27 6.07 8.32 7.52 7.46
Sorbus spp. 3.02 0.12 3.58 1.58 1.29 3.97 3.85 0.92 2.13
Trifolium hybridum ‘Frida’ 0.53 1.15 0.86 1.57 0.69 0.74 1.35 2.26 1.16
Trifolium pratense type 2.30 2.01 2.32 4.58 2.31 1.82 1.28 2.20 2.33
Trifolium repens type 9.61 16.28 9.84 13.35 9.28 13.67 8.69 11.44 11.88
Vaccinium spp. 1.09 3.20 2.42 4.33 3.48 2.52 1.39 3.78 2.88
Melliferous pollen types
with portion smaller than 2%
3.80 3.93 4.43 3.98 4.76 2.97 3.40 6.29 4.21
Non-melliferous
A
lnus spp. 2.17 0.56 2.77 1.29 1.10 0.70 2.99 0.28 1.51
A
nemone spp. 7.55 1.00 11.82 1.03 0.09 2.80 2.09 0.84 2.71
Betula spp. 3.77 0.96 3.65 3.08 0.73 1.32 2.99 0.09 2.30
Chenopodium spp. 1.23 0.36 0.58 0.62 0.23 0.39 2.09 0.21 0.86
Cyperaceae spp. 1.23 3.12 1.97 2.10 1.01 1.32 0.70 0.02 1.63
F
ilipendula spp. 40.57 54.44 41.36 64.44 77.32 72.94 63.31 72.83 62.26
Poaceae 6.79 15.36 9.26 7.01 6.20 8.71 8.87 4.72 8.65
Ranunculaceae 11.98 12.76 12.91 11.87 9.32 4.20 4.99 3.71 9.41
Rosa spp. 3.49 0.72 3.57 0.67 0.41 0.70 1.50 0.00 1.34
Rumex spp. 16.23 7.96 6.49 5.31 2.62 3.03 2.29 3.77 5.70
Non-melliferous pollen types
with portion smaller than 2%
5.00 2.76 5.62 2.59 0.96 3.89 8.18 13.52 3.64
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Pollen analyses of honey from Finland 287
largely replaced by Brassicaceae and Rosaceae
pollen (Figure 5). In the 1970s Brassicaceae pol-
len was clearly the dominant type, but it declined
by the 2000s to values almost equal to those of
Rosaceae (Figure 5). The proportion of the
Rosaceae pollen has increased by 15% and the
proportions of Asteraceae and Apiaceae pollen
have declined markedly from the late 1970s to
2006 (Figure 5).
Discussion
The present study provides new insights into the
pollen composition of Finnish honey. The honey
samples that were used in this study were collected
for controlling the quality and origin of honey sold
in Finland. Therefore samples were not taken from
some apiaries or at the same time of the year, and
the number of samples varied yearly. However, the
abundant number of the samples gives an adequate
picture of the pollen content of Finnish honey.
Pollen in honey originates from three main
sources: wild plants, those that are cultivated in
crops, or those planted in gardens. The pollen types
of wild growing plants are derived from typical Finn-
ish flora like Rubus arcticus, R. idaeus, R.
chamaemorus, Epilobium angustifolium, Calluna vul-
garis, Fragaria vesca, Menyanthes trifoliata, Anthyllis
vulneraria, Knautia arvensis, Tussilago farfara and
species of Vaccinium spp., Astragalus spp. and Salix
spp. and Rhamnaceae. Cultivated plants that are
commonly foraged and pollinated by bees in Finland
are the Brassicaceae family oil plants (B. rapa ssp.
oleifera and B. napus ssp. oleifera), Trifolium and
Phacelia species, Fagopyrum esculentum C. Moench,
and cultivated berries and fruit plants, such as Rubus
idaeus, R. arcticus, Fragaria vesca and the Malus spp.
and Pyrus spp. species. Phacelia spp. is cultivated by
Figure 4. The forage plants’ regions according to pollen type spectra in honey samples in the different administrative regions of Finland.
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288 A. Salonen et al.
beekeepers in order to provide forage plants for bees
during Autumn, and its pollen was found in 40% of
the honey samples. Some pollen types include pollen
of both cultivated and wild plant species. The most
important species are Brassicaceae, Rubus spp., Fra-
garia spp. and Trifolium spp. Salix spp. pollen occurs
commonly in honey samples, but never in high
proportions. Four of the pollen types observed in the
analyses (Acacia spp., Castanea sativa P. Mill,
Myrtaceae and Robinia pseudoacacia L.) are neither
native nor cultivated in Finland. These pollen types
most probably originate from imported pollen fed to
bees in cold Springs.
Based on frequency of occurrence and relative
proportions, the four most important plant groups
or species for bees in Finland are the Brassicaceae
family, Rubus spp. and Salix spp. species and Trifo-
lium spp. It was an unexpected finding that Trifolium
repens type had the highest frequency percentage and
that Fragaria spp. and Rubus spp. pollen is substan-
tially more frequent in the honey samples from the
2000s than has been observed in earlier studies. On
the other hand, we expected to find high values for
Epilobium spp., Vaccinium spp. and Calluna vulgaris
pollen types, because Finnish beekeepers know that
these plants produce large amounts of nectar for
honey bees in the eastern and northern parts of
Finland. However, the pollen grains of these plants
were present only in proportions of 0.35, 2.88 and
0.07% (respectively).
The nectar of Rubus idaeus attracts bees very effec-
tively because of its high sugar concentration and
the high quantity of the nectar (Crane et al., 1984).
It has also been noticed that, especially in those
years when the honey yield is good (2003, 2005 and
2006) (Anonymous, 2008), there are abundant
Rubus spp. pollen grains in the honey samples. The
frequency percentage of Rubus spp. was higher and
its proportion in the honey samples was markedly
higher than in the earlier pollen studies conducted in
Finland (Martimo, 1945; Aarnio, 1961; Varis et al.,
1982; Varis, 2000). This could be explained by
three factors. First, cultivation areas of Rubus idaeus
have increased since 1995 (Anonymous, 2008).
Berry growers commonly keep bees near cultivated
fields because of the importance of bee pollination
to berry yields. Second, the increase of wild Rubus
idaeus growing in forests may explain the increased
proportion of Rosaceae pollen types since 1960
(Figure 5), as wild Rubus idaeus has become more
common in Finnish forests from the 1950s to 1995
(Hotanen et al., 2000; Lampinen & Lahti, 2008).
The explanation lies in changes in silvicultural prac-
tices such as clear-felling creating favourable habitat
for pioneer plant species like R. idaeus (Hotanen
et al., 2000). Third, the beekeeping area has spread
to new regions in the eastern and northern parts of
the country. Samples from these areas contain more
pollen of wild plant species, as Brassica spp. is not
cultivated in these areas.
Pollen analyses do not reveal all aspects of the
botanical origin of honey, because the pollen grains
found in honey samples rarely correspond one-to-one
to the vegetation composition around the apiaries or
the floral types they represent (Bryant & Jones,
2001). For example, Myosis spp., with its minute
and numerous pollen grains, and Brassicaceae pol-
len are known to be over-represented in honey sam-
ples (Van der Ohe et al., 2004). Apiaceae pollen
type seems to be over-represented in honey samples
as well. Apiaceae pollen was found in over 90% of
the samples, but it represented a proportion of only
3% in the samples. Apiaceae taxa flower with large
populations at the end of June, when bees visit them
actively and collect large amounts of their pollen
grains. However, Apiaceae flowers produce only
small quantities of nectar (Ruottinen, 2005). On the
other hand, pollen of Epilobium spp. and Calluna
vulgaris seems to be under-represented in honey
samples (Van der Ohe et al., 2004; Bryant & Jones,
2001). In many areas of eastern and northern
Finland, bees produce large amounts of honey col-
lected from Calluna vulgaris and Epilobium angustifo-
lium. However, pollen from these taxa occurs in
small amounts even in unifloral honey (Ruottinen,
2005). The structure of the Epilobium angustifolium
flowers is such that bees are able to collect nectar
without touching the pollen bearing anthers, and the
pollen grains are so large that bees are easily able to
Figure 5. Percentage distribution of eight pollen types in Finnish
honey samples in 1960, 1962, 1963, 1977 and 1978 (Varis et al.,
1982) and in 2000, 2003 and 2007 (current study).
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Pollen analyses of honey from Finland 289
filter them out from the nectar (Bryant & Jones,
2001). The pollen content of these unifloral honeys
requires further investigation.
In the present study, one of the main interests was
to distinguish geographical regions in relation to the
forage plants of bees in Finland. About 70% of the
Finnish honey is produced in southern Finland,
Regions III and IV (Figure 4), (Heikki Vartiainen,
pers comm., 17/9/2008). In these two regions culti-
vated Brassica rapa ssp. oleifera forms the basis for
the effective honey production. This is clearly
reflected in the pollen assemblages of honey from
these areas. The importance of Rubus idaeus as a for-
age plant for bees can be seen in Region II, but the
amount of the pollen of Epilobium spp. was lower
than expected. One of the surprises was that high
proportions of Trifolium spp. pollen could be found
only in Northern Ostrobothnia. It was expected that
Trifolium spp. pollen would be found in high
number in the eastern part of Finland as well.
Marked changes have taken place in the relations
between Trifolium spp., Brassicaceae and Rosaceae
pollen in honey since the 1960s. At the end of the
1990s the amount of Brassicaceae pollen had
increased while the amount of Trifolium spp. type
pollen had decreased in samples. This phenomenon
is connected with changes in the cultivation areas of
these plants (Varis, 2000). The cultivation area of
Brassica rapa ssp. oleifera has increased by 40% from
1997 to 2006 (Anonymous, 2008). However, for
unknown reason, this increase was not observed in
the proportion of Brassicaceae pollen type in our
study in the 2000s (Figure 5).
The nearest and ecologically similar areas in the
neighbourhood of Finland where similar melissopaly-
nological studies have been contacted are in northern
Central Europe. Von der Ohe, W. and von der Ohe,
K. (1996) and Wróblewska and Stawiarz (2004)
have presented results of melissopalynological analy-
ses from Germany and Poland, respectively. Of the
ten most frequent pollen types observed in these
studies, five are the same as in our study (Trifolium
repens type, Rubus spp., Brassicaceae, Salix spp. and
Taraxacum spp.). On the other hand, Sorbus spp.,
Salix spp., Vaccinium spp., Rubus spp. and Epilobium
spp. pollen types are more frequent in Finland than
in Germany and Poland.
Conclusions
There have been profound changes in agri- and silvi-
culture in Finland since the 1960s. These are, for
example, the increased Brassica spp. cultivation in the
southern part of Finland and the more intense clear-
cuts of Pinus and Picea-forests all over in Finland.
These changes have markedly affected floristic
diversity, which is in turn reflected in the composition
of honey. A follow-up study is a good way to follow
these changes, to prevent honey adulteration and to
improve the quality of honey. Furthermore, more
research is needed on the unifloral honeys typical for
the boreal coniferous zone in order to investigate their
melissopalynological, organoleptical, physic-chemical
and production capacity properties.
Acknowledgements
The permission of the Finnish Beekeepers Associ-
ation is gratefully acknowledged for making the
results of the quality analyses of Finnish honey
available to us. The English usage was kindly
revised by Ms. Rosemary Mackenzie.
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