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ACTA AGROBOTANICA
Vol. 64 (2): 25–32
2011
THE BIOLOGY OF FLOWERING OF WINTER ACONITE
(Eranthis hyemalis (L.) SALISB.)
1Krystyna Rysiak, 2Beata Żuraw
1Botanical Garden of Maria-Curie Sklodowska University in Lublin, Sławinkowska 3, 20-810 Lublin, Poland
e-mail: rysiakk@hektor.umcs.lublin.pl
2Department of Botany, Laboratory of Horticultural Plant Biology, University of Life Sciences in Lublin,
Akademicka 15, 20-950 Lublin, Poland, e-mail: beata.zuraw@up.lublin.pl
Received: 07.01.2011
Abstract
Eranthis hyemalis belongs to the Ranunculaceae family
whose representatives enrich early spring pollen flow and nec-
tar for pollinating insects. Flowering biology and morphological
characteristics flowers of winter aconite were studied. The fora-
ge value was estimated as the rate of nectar production.
Observations were carried out between 2008 and 2011
in the Botanical Garden of the Maria Curie-Skłodowska Univer-
sity located in the Lublin area.
In the conditions of Lublin, flowering of winter aconi-
te plants started at the beginning of February and lasted until
the end of March. The seasonal bloom dynamics was strongly
affected by maximum temperatures, which intensified flower
blooming, and snowfalls which hampered this process. During
the day, flowers opened between 8.00 am and 3.00 pm, but the
highest intensity was between 10.00 am and 12.00 am. The pro-
cess of pollen release, with the average number of 29 stamens
shedding pollen in the flowers, lasted from 2 to 3 days. During
the day the largest number of anthers opened at noon hours,
between 11.00 am and 1.00 pm, though a certain rise in this
number was also observed in the morning hours between 8.00
and 9.00 am. Eranthis hyemalis flowers develop funnel-shaped
nectaries, on average 3-6 per flower. The determined amount
of nectar per flower was 1.23 mg, while the concentration of
sugars in it averaged 72.11%. The weight of nectar sugar per
flower was 0.88 mg.
Key words: winter aconite, Eranthis hyemalis, dynamics of
flowering, nectar, pollen release.
INTRODUCTION
The genus Eranthis Salisb. of the Ranun-
culaceae family occurs in the wild in Europe and
Asia (Walters et al. 1989; Szweykowscy,
2003). The above-mentioned genus comprises seven
(Walters et al. 1989; Szweykowscy, 2003) or
even ten species (Tutin et al. 1964).
Winter aconite (Eranthis hyemalis) occurs
in the wild in Europe from the south-eastern part of
France to Bulgaria (Szweykowscy, 2002). It co-
mes from the fertile forests of France, Italy, Slovenia,
Serbia, Bosnia, and Croatia (Polunin, 1969; E r -
hardt et al. 2002). It has been cultivated since 1570
(Marcinkowski, 2002) and has become wide-
spread all over Europe (Tutin et al. 1964; Wal-
ters et al. 1989). In Poland winter aconite occurs
sporadically in the western part of the country as a fe-
ral plant (Szweykowscy, 2003). It is also men-
tioned among ephemerophytes (Mirek et al. 2002).
This plant grows mainly among light thicket and sha-
dy groves (Amann, 1997). It is an ornament of old
parks (Szweykowscy, 2003). Winter aconite pro-
pagates profusely if the soil is sufficiently moist during
the spring (Amann, 1997). It perfectly reproduces
vegetatively by tubers and is not difficult in cultivation
(Marcinkowski, 2002).
Winter aconite is a small perennial plant with
a tuberous rhizome (Amann, 1997; Szweykow-
scy, 2003) or small spherical tubers (Walters et
al. 1989; Marcinkowski, 2002). A characteristic
feature of its plants is a whorl consisting of 5 deeply
dissected leaves (Strasburger et al. 1967). But
Szweykowscy (2003) report that there are three
stem leaves, sessile, palmately lobed, arranged in an
involucral whorl. The basal leaves, long-petiolate, pal-
mately lobed, with 5-7 linear sections, appear after flo-
wering cessation (Szweykowscy, 2003). The flo-
wers of winter aconite are yellow- or golden-coloured
and cup-shaped. They consist of 6 petals, 10-15 mm
in length. The diameter of flowers reaches 20-30 mm
Krystyna Rysiak, Beata Żuraw
26
(Tutin et al. 1964; Polunin, 1967; Amann,
1997; Marcinkowski, 2002). The flowers close
at 7 pm (Szweykowscy, 2003). There are necta-
ries in them (Szweykowscy, 2003).
The flowering period is at the turn of February
and March in western and central Europe (Core,
1955; Amann, 1997; Erhardt, 2002; Szwey-
kowscy, 2003). Marcinkowski (2002) reports
that in the Polish conditions blooming may extend
even into April.
The yellow-coloured flowers of plant species of
the buttercup family lure many pollinators (Amann,
1997; Lipiński, 2010) and can be a valuable so-
urce of pollen (Szklanowska, 1995; Denisow
and Żuraw, 2003). In the period when there is no
pollen, bees can not produce royal jelly or even be-
eswax, the mother bee stops laying eggs and larvae die
in the cells (Howes, 1979; Lipiński, 2010). In
most of the area of Poland, currently there is a shortage
of important early spring bee forage (J a b łoński,
1994). This is why flower gardens that provide to in-
sects an abundant and easy food source in the form of
nectar and pollen are of great importance (J a b łoń-
ski, 1994; K o łtowski, 2006).
The aim of the present study was to determine
the rate of flowering and pollen release of winter aco-
nite cultivated in gardens, which can be an excellent
supplement to the food resource for bees waking up
in the spring. The nectar production rate was also was
determined.
MATERIALS AND METHODS
The investigations were conducted in 2008-
2011 in the Botanical Garden of the Maria Curie-Skło-
dowska University located in the Lublin area. Speci-
mens of winter aconite (Eranthis hyemalis (L.) Salisb.)
growing in a dense patch on a slope, under the canopy
of a branchy maple, were selected for the observations.
This site had a south-eastern exposure. Every year the
flowering time was determined; the start of flowering
was determined to be when 10% of the plants in a de-
signated area opened the perianth leaves. In 2009 the
seasonal flowering rate was investigated and it was
analysed against the background of the atmospheric
conditions during the flowering period of the plants.
To this end, newly opened buds were counted every
day at 10 am in the designated area of 1 m2 and marked
with a coloured thread.
The daily rate of flower opening was analyzed
in 2009 every hour during a period of three days of
full bloom, by counting newly opened flowers on the
designated experimental area of 1 m2.
The duration of pollen release was examined in
2009. For this purpose, 5 new flowers that had started
shedding pollen were marked every 2 hours during 2
days of the full flowering period. Then, the number of
stamens that shed pollen was determined every 2 hours
until all the stamens in the flower were empty of pol-
len. In total, 50 flowers were observed.
The daily rate of pollen shed in the winter aco-
nite flowers was observed in 2010. To this end, the
number of stamens that had started shedding pollen
was counted in 10 flowers every hour during 3 days of
the full flowering period.
In 2011 the rate of nectar production in the
flowers was examined by J a b łoński’s method
(2003). In order to determine the weight of nectar,
12 samples with 5 flowers in each were collected. Nec-
tar sugar concentration was measured with an Abbe
refractometer. The nectaries in the flowers were exa-
mined under a stereoscopic microscope.
RESULTS AND DISCUSSION
Plant morphology. The tuberous rhizome is
an underground organ of winter aconite (Fig. 1b,c). It
can easily be divided into fragments that are single tu-
bers, which are described by Walter et al. (1989)
and Marcinkowski (2002). Winter aconite sel-
f-propagates through seeds, which readily germinate
shortly after they are shed from the follicles (Fig. 2a),
provided that there is adequate moisture in the soil.
Many young seedlings were observed in the observa-
tional plot which had suitable growth conditions. In
the first and second year after sowing, only long-pe-
tiolate palmate leaves grow out of the ground, charac-
terized by a deeply lobed leaf blade (Fig. 1a,b). In the
third year, flower stalks also grow out of the rhizomes
(Fig. 1c). One whorl, composed of three sessile, deeply
lobed leaves, occurs just below the flower on the stem
(Fig. 2), in accordance with a description by Szwey-
kowscy (2003). The leaves create a kind of ruff situ-
ated under the terminal flower (Figs 3-5). The flowers
of winter aconite reached a diameter between 2.5 cm
and 3.0 cm (Fig. 6). According with Szafer`s and
Wojtusiakowa`s (1969) classification, winter
aconite flowers are included in bowl-shaped flowers
with completely hidden nectaries (Fig. 6c). Many in-
sects from different groups have access to these flowers,
except insects with a short proboscis. These authors
say that this kind of nectaries are attractive for insects
because of their shape and colour (Fig. 7). Stamens in
the flowers are arranged spirally on an elongated floral
axis (Fig. 6d). Apocarpic gynoecium consisted from
3-5 free pistils with an elongated one-chambered ovary
and a stigma on a short style (Fig. 6e). After flowering,
elongated follicles appeared at the tip of the flower.
The flowering pattern. The development of
flowers took place in very early spring, and even in
The biology of flowering of winter aconite (Eranthis hyemalis (L.) Salisb.) 27
winter. Buds of winter aconite, covered by the ruff
the lobed leaves, grew out of the litter created from
the fallen leaves and fruit of the maple tree shading
them already at the end of January. The opening of
the first flowers started on February 5th (Table 1).
The estimated number of flowers per 1 m2 area ran-
ged from 224 in the first year to 350 in the last year
of the study (Table 1). Periodic decreases in tempe-
rature and snowfall in the initial period of flowering
of the plants inhibited the blooming of new flowers
(Fig. 8, 9), but did not damage the flowers. In the pe-
riod of deterioration in weather conditions and every
day around 7.00 pm, the perianth closed, probably
to protect the generative organs against low tempe-
ratures. During the day, new flowers opened around
9.00 am (Fig. 10). Depending on weather conditions,
the daily peak of flowering was between 10.00 and
12.00 am. The process of new buds opening was alre-
ady finished at 3.00 pm.
Pollen release. From 17 to 38 (on average 29)
stamens were estimated in one flower of winter aconite.
The process of pollen release took place from the lowest
located stamens on the axis of the flower. Temperature
and precipitation had the biggest influence on the pat-
tern of pollen release (Fig. 8, Table 2). Pollen shed in
the flower lasted from 2 to 3 days. The time of the day in
which pollen shed started had no effect on the intensity
of this process. Positive minimum temperature as well
as the absence of snowfall at the beginning of pollen re-
lease clearly accelerated the maturation of the anthers in
a flower. During the day, from 6 to 12 stamens shed pol-
len. Analyzing the daily dynamics of pollen shed, some
increase was noted in the morning as well as a distinct
peak in the afternoon (Fig. 11). After the stamens shed
pollen from their pollen sacs, they fell off.
The structure of the nectary and the process
of nectar secretion in flowers. Typically, 6 or 5 fun-
nel-shaped nectaries occurred in the flowers of winter
aconite (Figs 6c, 7). A similar number of nectaries,
with the same structure, is described by Żuraw and
Denisow (2002) in the flowers of Helleborus fo-
etidus. Occasionally, there were 3 or 4 nectaries in the
flower. Nectar appeared already in the initial phase
of pollen shed. The average weight of the nectar se-
creted from one flower was 1.23 mg and it was lower
by 0.23 mg than the values reported by Maurizio
and Grafl (1969). Nectar sugar concentration me-
asured with the refractometer ranged from 61.2% to
78% (on average 72.11%) and it was more than 46%
higher than that reported by the above-mentioned au-
thors. The calculated weight of sugars in the nectar
from one flower ranged from 0.64 mg to 1.14 mg (on
average 0.88 mg) and it was more than twice the amo-
unt specified by Maurizio and Grafl (1969) at
the level of 0.38 mg. The nectaries in the flowers of
winter aconite fell off at the same time as the latest
dehiscent anthers. The sepals became detached from
the receptacle as the last ones.
Visitation by pollinating insects. The flowers
of winter aconite attract insects by their smell as well
as the shape and colour of the yellow perianth. The
tissue of the perianth of winter aconite has the ability
to reflect UV rays in the same way as hellebore flowers
(Maurizio and Grafl, 1969). It is one of the ada-
ptations to honey bee visitation. The construction of
the eyes of the bee allows it to see the ultraviolet colour
range that is invisible to the human eye (Szafer and
Wojtusiakowa, 1969). During the study period,
on sunny windless days honeybee foragers were occa-
sionally observed on the flowers.
Table 1.
Flowering of the plants
during the study period (2008-2011)
Study year Time of owering e number of days in the
owering period Flowers x m-2
2008 5.02. – 10.03. 33 224
2009 25.02. – 20.03. 25 315
2010 3.03. – 19.03. 17 274
2011 7.02. - 22.03. 44 350
average 30 290.75
Krystyna Rysiak, Beata Żuraw
28
Fig. 1. Consecutive stages of plant growth and development: a –seedling; b – young rhizome (vegetative phase), c – mature rhizome
(generative phase), x 0.3
Fig. 2. Fruit setting stage: a –fruits (follicles); b –elongated axis of the flower (hypanthium); c – deep lobed bracts arranged in
a whorl, x 2
Fig. 3. Buds of Eranthis hyemalis growing out from between fallen maple leaves and fruits, x 0.2
Fig. 4. Flowers of Eranthis hyemalis surrounded by fresh snow, x 1
Fig. 5. Winter aconite at full bloom, x 1
Fig. 6. Flower cross section: a – floral bract; b – sepal; c – nectary; d – stamen; e – pistil
Fig. 7. Nectary: a –centripetal side; b – lateral view; c – centrifugal side
The biology of flowering of winter aconite (Eranthis hyemalis (L.) Salisb.) 29
-8
-6
-4
-2
0
2
4
6
8
10
02.03.09
03.03.09
04.03.09
05.03.09
06.03.09
07.03.09
08.03.09
09.03.09
10.03.09
11.03.09
12.03.09
13.03.09
14.03.09
15.03.09
16.03.09
17.03.09
18.03.09
19.03.09
20.03.09
21.03.09
22.03.09
23.03.09
24.03.09
date
oC, cm
snowfall in cm max. temp. in oC min. temp. in oC
Fig. 8. The distribution of selected weather parameters during flowering of winter aconite in 2009.
0
5
10
15
20
25
30
03.03.09
04.03.09
05.03.09
06.03.09
07.03.09
08.03.09
09.03.09
10.03.09
11.03.09
12.03.09
13.03.09
14.03.09
15.03.09
16.03.09
17.03.09
18.03.09
19.03.09
20.03.09
21.03.09
23.03.09
24.03.09
date
%
Fig. 9. The seasonal flowering pattern of Eranthis hyemalis flowers in 2009.
0
10
20
30
40
50
60
8.00 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00
hour
%
13.03.09 14.03.09 15.03.09
Fig. 10. The daily flowering rate on 13-15 March 2009.
Krystyna Rysiak, Beata Żuraw
30
Table 2.
Pollen release in Eranthis hyemalis flowers
Time of
ower
marking
e average number of stamens releasing pollen in one ower,
in the consecutive days of observation
e average
number of
stamens
in a ower
5.03.09 6.03.09 7.03.09
Reading time
08.00 10.00 12.00 14.00 16.00 08.00 10.00 12.00 14.00 16.00 08.00 10.00 12.00 14.00 16:00
5.03.09
08.00 2.6 4.0 1.2 2.6 0.2 0.6 0.6 0.4 0.6 0.6 3.8 4.4 0.4 1.2 22.6
10.00 2.2 1.4 1.2 0.2 0.8 2.8 1.6 1.4 1.4 2.4 7.4 2.0 24.8
12.00 2.2 1.6 0.4 0.8 3.4 3.2 2.6 2.6 5.8 4.0 26.6
14.00 3.0 1.0 5.8 3.2 1.6 1.2 2.0 3.5 4.0 1.6 26.9
16.00 3.0 6.8 2.2 1.6 1.4 4.8 7.0 1.4 0.0 0.4 28.6
6.03.09
08.00 2.4 3.4 0.8 2.8 2.8 12.0 3.6 27.8
10.00 2.4 1.4 3.4 4.4 13.0 1.6 26.2
12.00 2.8 4.4 5.6 11.0 1.0 24.8
14.00 3.2 4.4 13.0 6.6 1.0 28.2
16.00 4.4 8.0 13.0 1.8 27.2
0
5
10
15
20
25
30
9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00
hour
%
Fig. 11. The daily pollen release rate in Eranthis hyemalis flowers on 5 March 2010.
CONCLUSIONS
In the conditions of Lublin, the flowering of
winter aconite lasts from 5th February to 22nd March.
Snowfall occurring during the flowering of win-
ter aconite inhibits the opening of new buds, but it does
no damage to blooming buds.
Depending on weather conditions, during the
day new flowers open from 8.00 am to 3.00 pm.
The process of pollen release from the stamens,
with their average number of 29, lasts from 2 to 3
days.
The funnel-shaped nectaries secrete nectar in
the amount of 1.23 mg per flower and sugar concen-
tration is about 72%.
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Biologia kwitnienia rannika zimowego
[Eranthis hyemalis (l.) Salisb.]
Streszczenie
Eranthis hyemalis należy do rodziny Ranuncu-
laceae, której przedstawiciele wzbogacają wczesno-
wiosenny pożytek pyłkowy i nektarowy dla owadów
zapylających. Celem pracy było poznanie biologii
kwitnienia i cech morfologicznych kwiatów rannika
zimowego oraz wartości pożytkowej wyrażonej obfi-
tością nektarowania.
Obserwacje prowadzono w latach 2008-2011
na terenie Ogrodu Botanicznego UMCS w Lublinie.
W warunkach Lublina kwitnienie roślin trwało
od początku lutego do końca marca. Na sezonową dy-
namikę rozkwitania decydujący wpływ miały tempe-
ratury maksymalne, które intensyfikowały rozkwitanie
kwiatów, ale również opady śniegu, które całkowicie
hamowały ten proces. W ciągu dnia kwiaty rozkwitały
od godziny 8.00 do 15.00 z największym nasileniem
w godzinach 10.00-12.00. Proces pylenia pręcików
w liczbie średnio 29 w kwiecie trwał od 2 do 3 dni.
W ciągu dnia najwięcej pylników otwierało się w go-
dzinach południowych 11.00-13.00, choć zauważono
również pewną zwyżkę w godzinach porannych 8.00-
9.00. Kwiaty rannika wykształcają lejkowatego kształ-
tu listki miodnikowe w liczbie od 3 do 6. Oznaczona
ilość nektaru z 1 kwiatu wynosiła 1,23 mg, a koncen-
tracja cukrów w nim zawartych średnio 72,11%. Masa
cukrów oznaczonych z 1 kwiatu wynosiła 0,88 mg.
