Latvijas Universitāte
Pēteris Evarts-Bunders
Vītolu (Salix L.) ģints Latvijā
Genus Willows (Salix L.) in Latvia
Promocijas darba kopsavilkums
Bioloģijas doktora zinātniskā grāda iegūšanai
Bioloģijas apakšnozare - botānika
Rīga 2005
Genus Willows (Salix L.) in Latvia
Importance of the study
Willow (Salix L.) genus is one of the most widespread plants in temperate climatic zone of the
Northern hemisphere and one of the richest in the Latvian dendroflora. Naturally there are 20 species of
this genus that are native or became naturalized in different periods, as welt as several subspecies,
varieties and more than 60 hybrids. Species of willow genus have a dominating role in plant
communities in areas with raised soil moisture, especially along rivers and lakes, in humid,
overgrown meadows, often also in synantropic ecosystems transformed by humans.
Latvian countryside landscapes, old manor parks, as well as city municipal green areas are not
imaginable without big willow species. Since at least the beginning of the 19 century several
exceptionally decorative willow varieties have become well-known in Baltic region, such as S. alba
'Sericea', S. alba 'Vitellina', S. fragilis 'Bullata' etc., which can be found also nowadays in plant
assortments offered by every large arboretum and they are very marketable.
Besides decorative gardening, willows and osiers are used also for different economic needs:
cheap wood due to rapid growth specific to these species, to stabilize hillsides, coasts, sand dunes and
sands against wiud and water erosion, to make anti-snow plantations along roads and for wattleworks. Furthermore willows and osiers are used in several other branches of the economy. They are
used for extraction of different organic compounds (e.g., salicine, tannin, etc.), and for biological
cleaning of waste water.
The Willow genus has for along time been considered as very complicated and inconvenient for
taxonomy. The species definition is complicated by various hybrids, species morphological diversity
and variation in specific ecological conditions. This genus has been examined by several well-known
Latvian natural scientists - A. Kupfer, E. Lehmann, K.Starcs, A.Rasiņš, R.Cinovskis and others.
Although the achievement of these and many other specialists is enormous and invaluable, there is
still no consistency and clarity in many questions connected to the nomenclature of some willow
genus species, their distribution, spread of morphological limits, interspecific hybridization problem,
native species, etc. The taxonomic limits of several species are vague and uncertain, they come out
with features of other species. The above-mentioned difficulties are the reason why there is no unity in
species descriptions and identification keys of different authors.
A. Rasiņš published the last all-encompassing work about the willow genus in 1959. Fourty five
years have passed since, and during this time the inventery level and knowledge of this genus has
improved significantly. Personal research, herbarium inventery and analysis of willow material
growing in dendfarium of the National Botanical garden (approximately 250 taxons), were used to
develop new concept of the genus taxonomy, distribution and hybridization.
The following problems were marked as priorities in the work on the willow genus in Latvia:
1. Concretizatton of the species distribution which grow on border of their spreading area (S.
phylicifolia. S. burjatica) in Latvia, as well as for species wilh heterogenous distribution in
Latvia (S. lapponum, S. daphnoides). Determination of species occurrence, with emphasis on the
distribution of protected species.
2. Definition of the whole complex of essential morphological and other characteristics to
determine interspecific limits. Assessing the need to divide several intrerspecific taxons.
3. Interspecific hybridization. Hybrid occurrence, definition of their specific traits.
4. Autochtonity of several species (S. alba, S.fragilis. S. acutifolia).
Aims and tasks of the study
Aims of the study:
To determine the occurrence of willow species in Latvia. To determine taxons requiring a special
protection regime. To determine the set of traits used in species definition, to describe the the limits of
characters for each taxon and to creating a conceptually new species identification key. To evaluate the
importance of many intraspecific taxons and hybrids in Latvia and in Baltic region in general.
Main tasks of the study:
1. To collect and to summarize material about the taxons, ecology, occurrence and hybridization
of the willow genus, covering as many diverse biotopes as possible in the whole territory of
Latvia.
2. To summarize the herbaria material available for public use in Latvia (LU Faculty of Biology,
LU Institute of Biology, National Botanical garden, Daugavpils University, Tei či Nature
reserve, etc) regarding the Salix genus.
3. Based on collected material and herbarium material analysis, to determine the essential
morphologic features for identification, to create maps of species occurrence. To analyze the
morphologic features and occurrence of willow hybrids in Latvia.
4. To describe the morphological features of willow species and intraspecific taxons collected in
the dendrarium of the National Botanical garden.
5. To summarize all published work about the willow genus in Latvia.
Scientific novelty and practical usefulness of the study
1. We summarized information about previous research on willow genus taxonomy in Latvia and
the Baltic region.
2. We conducted analysis of all the willow genus material available in herbaria in the Baltic
States.
3. We created original species descriptions, definition charts, maps of occurrence for the rarest
species, we evaluated material about interspecific hybridization, and for the first time Latvian
names were given to several nothospecies.
4 We critically evaluated many forms of willow species, cultivating vegetatively multiplied plant
material, grown in similar ecological conditions. The work showed that many form distinctions
disappeared. Forms that were previously mentioned in the most significant research published in
the Baltic States proved to be taxonomicatly insignificant.
5. We identified S. pomeranica as a separate species for the first time, S. viminalis var. rossica
was determined as a new taxon. For the first time, the occurrence of S. repens in Latvia was
proved using herbarium material. For the first time S. acutifiolia was proved as a native species
in Latvia, which was only known from plant nurseries till now.
6. Complementing and revising dendrological collections, one of the largest willow collection in
the Eastern Europe was created in the National Botanical garden (approximately 250 taxonomic
units), including all wild species, subspecies and varieties growing in Latvia, as well as the
majority of hybrids which were obtained from the wild or from other largest European
collections (Yekaterinburg, Brno, Pruhonice).
Approbation of the study
The research and conclusions made have been published in reports and papers by the author at several
international scientific conferences:
1. Conference of Voung scientists of Cast European countries: "Problems of dendrology,
floriculture and pomology" (Yalta, Ukraine, 1998).
2. Conference of East European Botanical gardens: "Plant genefund accumulation, evaluation and
protection in the botanical gardens" (Vilnius, Lithuania, 1999)
3. Conference of European dendrologists "Problems of dendrology at the border of the XXX
century" (Moscow, Russia, 1999).
4. Conference dedicated to the problems of conservation of biological diversity "Research and
conservation of biological diversity in Baltic region" (Daugavpils, Latvia, 2001).
5. Conference dedicated to the problems of conservation of biological diversity "Biological
diversity, ecology, evolution, adaptation" (Odessa, Ukraine, 2003).
6. Conference dedicated to the problems of conservation of biological diversity "Research and
conservation of biological diversity in Baltic region" (Daugavpils, Latvia, 2003).
7. Conference dedicated to the problems of conservation of biological diversity "Research and
conservation of biological diversity in Baltic region" (Daugavpils, Latvia, 2005).
Description of the theme of the study
1. The history of studies of willows in Latvia
Information on willows growing in the territory of Latvia appeared for the first time in the second
half of the XVIII century in the work of J.Fischer (Fischer 1778, 1784, 1791). In his first edition
Fischer mentions 6 species of the willow genus: Salix alba, S. viminalis, S. caprea, S. aurita, S. repens
and S. arenaria. In the addendum of 1784 Fischer mentions 4 more species - S. fragilis, S.
rosmarinifolia, S. amygdalina and S. phylicifolia, but in the work of 1791 the number of species
reaches 13 (S. pentandra was mentioned for the first time). Grindel in his work names 18 species
(Grindel 1803); later he names another 5 species (S. vitellina, S. myrsinites, S. glauca, S. lanata and
S.cinerea). J. Friebe in his book about the flora of Vidzeme, Kurzeme and Estonia (Friebe 1805)
mentions 11 wild species of the willow genus, and he reasonably deletes several species mentioned by
the previous authors from the list of species. At this time the first specific research about the genus
Salix in Vidzeme was published (Trautvetter 1832), which is considered as the first work devoted to
this topic in Russia.
The flora of Fleisher and Lindemann contains more 20 species of willow genus, as well as a list of
multiple forms and annotations (Fleischer, Lindemann 1839), in this work species such as S.
acutifolia and S. daphnoides were mentioned for the first time. The second edition is richer in species
and forms (Fleischer, Bunge 1853). However, not only in this work but also in many other work, the
biggest problem is hybrid definition, which causes a number of uncertainties and misunderstanding.
Similar problems can be also noticed in the work by Wiedemann and Weber about the plants of
Estonia, Kurzeme and Vidzeme (Wiedemann, Weber 1852).
The work by J. Klinge about the flora of Estonia, Vidzeme and Kurzeme is much more complete
(Klinge 1882); 19 species of willow genus are mentioned, and most are given correctly. Only a few S. silesiaca, S. hastata and S. arbuscula are noted incorrectly according to our modem understanding.
More material is given in the first dendraflora review in the Baltic region Die Holzgewachse von Est-,
Liv- und Curland (Klinge 1883).
The flora of Poland and Vidzeme by Eduard Lehmann and its sequel published later (Lehmann
1895, 1896) is considered as one of the best work of the 19 century. In his work Lehmann mentioned
locations for all species, and his lists of rare and unclear taxons are especially valuable Considering his
data collected in Latgale, the flora by Lehmann has not lost its importance up to date.
At the turn of the century, the well-known nature scientists K Kupffer and P. Lakschevitz carried out
research about the willow genus in Latvia. Unfortunately these scientists did not summarize their
research on Salix in scientific publications, but important information can be found on the accurately
filled herbaria labels, as well as in references in the work by oth er authors (Seemen 1908-1910;
Toepfer 1925-1927).
The trees and shrubs identification manual by K. Starcs (Starcs 1925) gives detailed analysis of
species and hybrids of the willow genus. Similar material can be found in the spring plant identification
manual published by Stares (1924/27). K. Starcs summarized his research on the willow genus in his
diploma paper "Preliminary work and materials for the monograph of Latvian genus Salix L." (Stares
1929).
After the Second World War A. Rasiņš carried out more extensive research, which was
summarized in the publication "Ivy Latvijskoi SSR" (Rasiņš 1959). In this work, attention is generally
given to willows and osiers that grow in river valleys. The analysis of morphological characters is only
given for a few species, most often with comment that supplementary research is needed. The summary
of the willow genus in the second volume of the Latvian SSR flora was made by P. (Galenieks
(Galenieks 1955). Willow identification keys can also be found in the plant handbook of the Latvian
SSR, in which characters are divided into two groups - vegetative and generative (Pētersone 1958,
1980).
Interpretation of the morphological limits of several taxons of willow genus (Cinovskis 1979) and
the occurrence of trees and shrubs in several administrative districts can be found in some editions
about the research carried out in the Dendroflora Laboratory, directed by R. Cinovskis.
Since 1994, P. Evarts-Bunders has carried out research on the willow genus, paying special
attention to the taxon systematics, occurrence and hybridization.
2. Study material and methods
The work on willow genus taxonomy and occurrence of species started in 1994. The initial
research area was Daugavpils district, where the analysis of the willow genus was earned out till 1997
and served as a model for later research in the whole territory of Latvia.
The main directions of the research were taxonomy, phytogeography (species horology),
cultivation of vegetatively grown samples and morphological analysis.
The research was based on the available herbarium material, as well as on extensive field survey
(Fig.l). The method of taxonomical transect which was recommended by A. Skvortsov (Skvortsov
1968, 1999) was chosen as the best method for field survey of the willow genus. It is necessary to
choose an area that is rich in the willow genus, and following a definite route, to identify all willows.
This method can provide suitable material to determine the variation range of morphological,
anatomical, ecological and phenological features of the willow genus and to determine their featur e
spectrum which is needed for identifying taxons. The field stusies encompassed all floral geographical
areas, and covered most botanical grid squares lacking herbarium material, and in the areas where the
occurrence of a critical taxon in Latvia can be predicted from the herbarium of a neighbor country or
the analysis of literature. For example, important areas for field study were coastal lowland (occurrence
of S. repens and S. daphnoides). Northern Vidzeine and Northern Lalgale (occurrence of S. phylicifolia
and S. viminalis var. rossica), South-East Latvia, the valley of Daugava and Sēlija (native species 8.
acutifolia, S. alba), Gauja river basin (occurrence of S. pomeranica).
Fig. 1. Map of botanical quadrates of Latvia with location of field study areas.
The research included as diverse biotopes as possible, as one of the biggest disadvantages of the
previous research was the uniformity of the surveyed biotopes, e.g., A.Rasiņš studied mostly willows
along rivers and lake banks. Biotopes with anthropogenic influence were studied detail. Disturbe d
places such as waste areas, roadsides, embankments, abandoned military objects ate biotopes where
hybridospecies appear relatively more often, as the range expansion of several species occurrence
occurs through these locations (S. purpurea, S. burjatica, S. alba). The analysis of rarely examined
autochthonous and subspontaneous willow species around old countryside parks is important. Since the
18th century forms of cultivated S. alba, S. fragilis, S. daphnoides and their decorative forms have
escaped to the wild in many places, indicating the allochthon origin of the species in Latvia.
The division of Latvian willow species into sections is based on the scheme created by A.
Skvortsov (Skvortsov l982, 1999).
Species descriptions and map of occurrence were created based on personal observations in
nature and in the scientific arboretum and dendranum of the National Botanical Garden, as well as
analysis of the herbarium materials available. Unpublished data of A. Rasiņš on morphometric indices
of characters were used.
In the willow collection of the dendrarium of the National Botanical Garden (NBG), there are 20
species of the willow genus that grow wild in Latvia, as well as various uncertain intraspecific taxons
(mostly forms). Cultivation of many previously considered forms of willow in the dendrarium proved
their taxonomical insignificance. Morphological features are widely variable among different
ecological conditions, which was the reason for the distribution of many forms in the Baltic region
When cultivated these morphological differences disappear. The natural hybrids were collected mostly
in Latvia. Many artificially produced hybrids that served generally as material for comparison came
from Yekaterinburg (Russia), Brno and Pruhonice (Czech Republic). The total number of units in the
collection is more than 270, which is the largest collection of the willow genus in the Baltic region. The
volume of the collection and the diversity of its forms correspond to the universal requirements for
collections.
All figures and maps of occurrence in the work are original work.
A total of approximately 1200 herbarium samples were collected, mostly from the places where
there was a lack of materials in Latvian herbaria, as well as about species with an unclear occurrence
and systematic status. These herbarium samples are stored in the Department of Dendroflora, NBG,
and tn the herbarium of Daugavpils University,
Within the frameworks of the work we conducted analysis of the herbarium material available in
Latvia and in neighbouring countries - Lithuania, Estonia and Russia:
DAU - Herbarium of the Daugavpils University
HBN - Herbarium of the Department of Dendroflora, National Botanical Garden.
LATV -Herbarium of the Botanical laboratory, LU Institute of Biology.
LDM - Herbarium of the Natural History Museum of Latvia.
Herbarium of the Lithuanian Institute of Botany.
LLU — Herbarium of the Latvian University of Agriculture.
RAS - A. Rasiņš Herbarium.
RIG I - K. Kupffer Herbarium (LU Faculty of Biology).
RIG II - LU Faculty of Biology herbarium.
RIG III - P.Lakschevitz Herbarium (LU Faculty of Biology).
RIG IV - K. Starcs Herbarium (LU Faculty of Biology)
LE - Herbarium of the St-Petersburg Institute of Botany a.h. Komarov (partly).
SVR — Herbarium of Slītere National park.
TAA- Herbarium of Tartu Institute of Botany and Zoology.
TU - Herbarium of Tartu University.
TVR - Herbarium of Teici Nature Reserve.
WI - Herbarium of Vilnius University.
3. Ecological distinction of genus Salix
Species of the willow genus are heliophilous trees and shrubs of moist soils. In the places where
there is water deficit, they only grow on river and lake sides, and in seashore sands (in this case they
are mostly artificially planted). Many trees of this genus growing in dry places have more leaves than
in other biotopes, e.g., S. alba, S. rosmarinifolia and S. burjatica. These ecological forms are often
described as independent intraspecific taxons - form or variety, also in the Baltic region (Pētersone
1955; Rasiņš 1959; Smaliukas 1996, 1997). If they are vegetatively reproduced and planted in the same
growing conditions in the National Botanical Garden, these differences disappear. If there is sufficient
moisture, they can grow in various biotopes. These ecological features are reflected in the seed
structure. Seeds are small, with filaments, adapted to sowing by wind. Seeds contain a completely
formed embryo, and there are almost no reserves of nutrient substances,
In Latvia in most of Salix species, seeds mature at the end of May or in June. After tailing on
moist, well-lightened soil, seeds germinate on the first day, and a new individual will grow till autumn.
S. pentandra seeds develop later and only germinate next spring. This is one of the features that allows
osiers and willows to occupy new areas.
An important feature of osiers and willows along river sides is the ability of broken branches
brought by the stream to a shore to produce new plants, especially in spring at the time of high w ater.
This explains the wide occurrence of S. alba, S. fragilis and other species along the river sides of
Daugava and other rivers. In this way S. acutifolia arrived from Northern Byelorussia where the wild
form ranges is in the upper part of Daugava
We must note that a specific community of species usually characterizes each biotope. In Latvia the
typical species of low and transitional mires are S. lapponum, S. myrtilloides. S. rosmarinifolia. Often
also S. aurita S. viminalis and S. triandra form homogenous stands along rivers and lakes. S. cinerea,
S. pentandra and S. starkeana are common in flooded meadows, moist edges of forests and mires. S,
caprea is a typical species that grows in the forest understorey, more rarely, in the subcanopy, it is the
only Satix species in Latvia that can tolerate partial darkening. Therefore research carried out only in
one of few biotopes will give uncorrect results of species occurence. In the herbaria materia collected
previously by Latvian researchers, rivers and lakes side species dominate in the collections, including
Kupffer and Rasiņš collections.
It is considered that Satix species are undemanding regarding the soil pH level (Skvortsov 1968,
Sommerville 1992), the tendency to grow in the soils with pH lower than 6. 5 is associated to moisture
regime in those biotopes.
The Salix species have different requirement for soil nutrients. For example, S. repens, S.
acutifolia and S. daphnoides can grow and develop in sandy soils that are poor with nutrient
substances. The majority of species prefer richer examples of soils. Such species are S. cinerea, S.
caprea and S. myrsinifolia.
Willows and osiers tolerate anthropogenic impact and can grow in biotopes transformed or
disturbed by people; they often grow in places where other trees and shrubs are not able to grow due to
erosion, pollution and other factors. These secondary soils have become characteristic for some species,
e.g., S. myrsinifolia, S. purpurea, making it is sometimes difficult to determine their optimum soil type
in natural conditions. Hybrid occurrence is increased in disturbed biotopes, where S. x multinervis Doll,
S. x rubra Huds, a.o. are common.
4. Analysis of morphological features which are essential in identification
In different literature sources there are references to the various features that can be used to define
Salix species. These identification schemes are usually based on differences in generative organ
structures or the complete complex of vegetative characters. There has been efforts to develope a
species identification key for use in winter, based on shoot and bud differences (Skvortsov 1968).
However, significant species plasticity and genetic polymorphism require using as large as possible
numbers of features, as one specific species feature can not usually be found in all specimens of the
taxon. Therefore characteristics are integrated in a unified system, defining features that best describe
efficient each specific sample.
•
Habitus.
Relatively few Salix species in Latvia reach the tree canopy or subcanopy Examples are S. alba, S.
fragilis and its hybrid S. x rubens. S. caprea can attain a height of 20m. S. daphnoides can attain a
height of 15-20m. S. acutifolia, S. viminalis var. rossica, S. pentandra and S. burjaticas can be
considered as trees reaching sapling size. Therefore the word "willow" ("vītols" in Latvian) must be
used in Latvian epithets of these species. However, the above-mentioned willows usually do not grow as
high. The other trees of Salix genus that range in Latvia are shrubs or dwarf shrubs (S.myrtilloides).
•
Bark and shoots.
The bark of large trees is usually very creviced; the bark of younger specimens is smooth.
S. triandra is characterized cinnamon brown inner bark that appears after breaking of the old bark into
irregular flakes. A significant feature is the colour of the 2 - 3 last year branches. Some species are
pruinose with a dense glaucous bloom (Daphnella section). Various decorative forms are identified by
the colour of shoots and the pendulant branches. On older branches, the features become less clear and
more complicated to determine. The thickness of the last-year shoot is an important feature. Thus, e.g.,
the ends of new shoots of S. acutifolia are approximately 1 mm in diameter, which is not characteristic
for other species of the section. A considerably important character is the case when the last-year
shoots (S. fragilis) are fragile or glossy. The bark can have a certain colour from the inside. Thus, e.g.,
the bark of S. daphnoides is lemon coloured from the inside and has a bitter taste. Some species of the
Vetrix section (S. cinerea, S. aurita) are characterized by wood walls. This is an important feature of
the above mentioned species hybrids. Some authors mention the length of these wails as an important
character (Rasiņš l958; Chmelar, Meusel 1979). The importance of this feature is still unclear.
• Buds
Duds are important for identification, especially their colour (e.g., S. starkeana buds are carmine),
also hairiness and form of bud tips (pointed, rounded, and bent). It is important to note if the buds are
orientated in a certain angle to the trunk. As an example we can mention 8. cinerea which has partly
ascending buds. It is important to know the size and the form of the bud, and if the buds are flat. These
latter features are usually well expressed and very consistent.
The arrangement of vegetative and generative buds on a shoot are characters that describes on the
whole several sections. Three types can be found (Skvortsov 1968) of which two can be found in
Latvia:
1."Alba" type. Changes in bud size occur gradually. The 4th - 7th buds are the largest
2."Caprea" type. The exterior of generative and vegetative buds differs. The first 3 - 6 buds are small
vegetative buds, then the next 2 - 7 are big generative and then the others are small vegetative buds.
• Leaves and stipules
The morphological features of leaves are relatively variable. We must take into consideration mat
the inferior leaves of shoots usually do not develop completely, which is why they cannot be used for
identification. It is complicated and even almost impossible to identify the species using new shoots,
sprouts. Their leaves are usually large and have a modified form. In the identification of Salix species,
it is necessary to pay attention to the form of leaf, the patterns of size, len gth and width, colour and
level of hairiness on both sides of leaves, length of pedicle, form of leaf margins (even, dentate, lobate),
position where the leaf blade is the widest (middle, upper or lower third: particularly important for
identification of species and intraspecific taxons of the Vimen section). The form of leaf blade is very
variable in various species (S. myrsinifolia, S. cinerea) However, leaf colour is a relatively stable sign.
One of the important features for the identification of the extremely polymorphous S. myrsinifolia is the
green leaf tip on the leaf lower side, where the leaf begins to grow black Significant characters are the
form of leaf base and tip, venation; the number of side veins is an important sign for identification of
several similar species, such as S. repens and S. rosmarinifolia.
The stipules give the important information, although they defoliate soon after the opening of
leaves. It is necessary to note the form and size of stipules, their tip and the arrangement of glands.
• Flowers and fruit
These characters can be used during a very limited period of lime; they can be used in
identification before the opening of leaves or when the leaves are not sufficiently developed for almost
all species (except S. pentandra). Therefore, in the present work, vegetative signs are emphasized
mostly excepting some cases.
The times of leave and generative organ development have to be taken into consideration.
Catkins can develop before the opening of leaves (S. acutifolia), simultaneously with leaves
(S.fragilis) or after the opening of leaves (S. pentandra). This feature varies within the area an is
expressed in introduced taxons.
The most important characters of female flowers are the colour of flower petals, hairiness and form
of primordium, pistil pedicle and nectary sizes, and the size and the colour of stigma.
The most important characters of male flowers are the number of stamens (stable sign: S.
triandra - 3, S. pentandra - 5, other species - 2 stamens), the colour of the flower petal, hairiness of
filaments and the colour of stamens. The size, form and colour of catkins must be taken into
consideration. A relatively stable sign is the form, size and hairiness of the capsule, which can be used in
determination in some cases.
Many features became very variable in the conditions of Latvia and the Baltic region (e.g., the
colour of flower petal) and they can only be used in determination conditionally. In our research, only a
few characters were acknowledged as significant generative signs for species identification, e.g.,
hairiness of primordium, hairiness of capsule for differentiation of S.rosmarinifolia and S.repens, the
length of pistil pedicle in determination of S.viminalis intaspecific taxons.
Various groups of features that are successfully used in determination of other genus proved to be
inapplicable in the case of Salix species. Pollen, (Erdtman 1986) and seeds proved to be extremely
similar, morphological structure and number of chromosomes can not be used in determination, as
chromosomes of Salix species are tiny, similar, their number varies within species (Rechinger 1981)
and is mostly the same: n=l 9.
4. Taxa of willow genus in Latvia
Genus: Salix L. Linnaeus, 1753, Sp. Pl.: 1015, 1754, Gen. Pl. ed. 5: 447.
There are 330 - 350 species in the Salix genus (Skvortsov 1999). Other authors mention a
different number of species: 300 species (Hillier, Coombes 2002), (Rehder 1956)
18 species are considered as autochthonous in Latvia. The widespread crack willow (S. fragilis)
should be considered as archeophyte, it has been planted near populated areas due to its decorative
features from where it naturalized. S. daphnoides has been used for stabilizing sands since the middle
of the 19 century and has become naturalized, this is why sometimes it is incorrectly considered as
native. S. acutifolia which was considered as cultivated in Latvia till present, was found as native in the
districts of Daugavpils, Krāslava and Gulbene during our research. Salix alba has escaped to the wild in
most territory of Latvia, similar to Salix fragils. Native localites of Salix alba are situated along river
sides of Daugava and Gauja and their largest confluents.
The 20 Salix taxons in Latvia belong to 3 subgenus and 11 sections.
Subgenus Salix
Sect. Amygdalinae Koch, 1837, Syn. Fl. Germ. Helv.: 644.
Salix triandra L., 1753, Sp. Pl. : 1016, Friebe, 1805, Fl. Liefl. Ehstl. Kurl. : 82.
The basic species of Salix triandra in its distribution range (also in Latvia) is not homogenous.
There are 2 different forms with quite uniform characteristics.
1.
S. triandra f. discolor (Koch) C.K. Schneid. Form with bluish wax coat at the bottom of leaves
and slightly narrow leaves with senate margins. Rasiņš mentions this form as var. glaucophylla Ser.
2
S. triandra f. concolor (Koch) C.K. Schneid. The bottom of the leaf is green, without a wax
coat, it does not differ from the colour on the top of the leaf. Leaves are wider with proportionally less
expressed serrate margins.
A. Rasiņš in Latvia (Rasiņš 1958) and D. Smaliukas in Lithuania (Smaliukas 1996) mention
several forms of Salix triandra, as well as species of other genus — f . elliptica Ser., f. latifolia Schatz.,
f. angustifolia Ser., etc. Most probably these forms are the result of natural species variability in
different ecological conditions; therefore, they should be considered as taxonomically insignificant and
they are not considered further
Sect. Pentandrae (Boner) C. K. Schneid., !904, Handb. 1 : 29.
Salix pentandra L., 1753, Sp. Pl: 1016, J. Fisch., 1791, Vers. Natrurg. Livl, 2. Aufl: 636, sine auct.
In all territory of the area, also in Latvia, the group of species morphological characters is
relatively stable and slightly varies; therefore, taxonomically significant wild intraspecific taxons are
not distinguished.
Sect. Salix
Salix alba L., 1753, Sp. Pl: 1021; J. Fisch., 1778, Vers Naturg. Livl.: 301, sine auct.
This species has been cultivated in Latvia for at least 3 centuries, and according to the
observations in the National Botanical Garden and a number of Latvian old parks, it become to spread
rapidly. Species expansivity is the reason why there is still no completely clear natural northern limit of
species occurrence (Skvortsov 1968; Meikle 1984, 1992). White willow has not naturalized in Great
Britain, Holland, Denmark and Estonia (Jalas, Suominen 1987). It has been considered that the species
is an autochthonous element of the flora in Latvia, and the limit of its natural occurrence extends more
or less along the state border between Estonia and Latvia (Rasiņš 1958; Krall, Viljasoo 1971). The
forms widespread in Latvia have silvery leaves or bright orange-yellow shoots, which is a decorative
variety, not a nominal form which exists within its natural area, especially near to old rural parks, in
different biotopes transformed by people and in places where it had been previously planted. We
consider that the Latvian species in most areas is not autochthonous, but it obtained the status of a local
species due to its rapid spread and hybridization with other species The native Latvian species can be
found most probably on the river shores of the Daugava (especially in the Nature park "Daugavas
Loki") and Gauja, as well as their largest tributaries, where it is spread by broken branches in spring
flood. The collected material corresponds to the description of the main species.
Salix fragilis L., 1753, Sp Pl.: 1017; J. Fisch., 1784, Zusarze Vers. Naturg. Livl.: 138, sine auct.
This species can be found in Latvia as separate clones. Hybrids with S. alba are often called as S.
fragilis, which not prevent earlier calling the species autochthonous, e.g., in the work by A. Rasi ņš
(Rasiņš 1958). It is correctly considered as a cultivated species foreign to the wild flora in Estonia
(Krall, Viljasoo 1965). Fleischer and Lindemann (Fleischer, Lindemann 1839) indicated that Latvian
S. fragilis is not homogenous. The most widespread clones in Latvia are:
"Decipiens" (S. fragilis var. decipiens (Hoffm.) Koch, S. decipiens Hoffm.). A small tree with
dull shoots and bright leaves. Masculine clone, often found in cultures. The variety description
corresponds to the group of taxon morphological characters which is often considered as crack willow
in the Baltic region.
"Russeliana" (S. fragilis var. russeliana (Sm.) Koch, S. russeliana Sm). The features of the
clone correspond more to the hybrid with S. alba (S x rubens Schrank in modern perception). Feminine
clone. Other mentioned varieties - var. vulgaris Koch, var. angustifolia Wimmer (Lehmann 1895,
Stares 1925) have no taxonomic significance.
Subgenus Chamaetia (Dumort) Nasarov, 1936, Фл. CCCP 5: 31. Sect.
Myrtilloides Koehne, 1893, Dendr: 89, 102.
Salix myrtilloides L.,1753, Sp. Pl.: 1019; J. Fleisch. und Em. Lindem., 1839, in J. Fleischer., Fl.
Esth. Liv. Kurl. : 346.
This species can be found in Latvia heterogeneously. Its occurrence border is along the line Riga Jelgava - Jūrmala. Contrary to the existing opinion, Salix myrtilloides can also be found as separate
swards in Kurzeme around Lake Engure, near Liepaja and in Pape. However, this species mostly is
located in central and northern parts of Vidzeme and in the northern Latgale Several sites were
mentioned in the flora of Poland and Vidzeme by E. Lehmann - Balvi, Medumi, Ruskulova and Zalve,
but confirming herbaria have not survived The most southern location of the species in Latvia was
found in Baltmuiža bog, Subate pagasts, Daugavpils district (Fig. 2).
Subgenus Vetrix Dumort. 1862, Bull. Soc. Bot. Belg. 1: 141.
Sect. Nigricantes Kerner, 1860,N.-Ost Weid. : 235.
Salix myrsinifolia Salisb 1796, Prod. Stirp. Allert: 394; Bickis et Rasiņš, 1946, In Bickis, Latv. augu
not: 132.
One of the most common species of the willow genus in Latvia. It grows along moist edges of
forests, in humid meadows, shrubs. It is widespread in different anthropogenic biotopes - roadsides,
embankments, and fallows. This willow species is one of the most polymorphic and most complicated
to determine in Europe (Skvortsov 1968) which is dramatically shown by the number synonyms given
in the nomenclature part of the species description.
Several forms and varieties have been mentioned in the flora of the Baltic region: f. rotundata
(Forbes) Hartig., f. ovata Toepfer., F. ovato-lancealata Toepfer., f. obovata (A.Mayer) Toepfer, etc.
(Galenieks 1955, Rasinsh 1959, Smaliukas 1996), their distinctive characters are mostly the forms of
leaves. However, considering the variety of species morphological characters, the taxonomical
significance of these forms is unfounded, shown in the studies earned out in the dendrarium of
National Botanical Garden.
Well discernible samples with large, dermatoid, bilaterally green leaves that do not blacken can be
found in the herbarium materials of Latvia and Lithuania. These samples were named var.
lithuanica Bess, in the work by J. Klinge (Klinge 1882) The division of this taxon seems reasonable,
but the distribution of the taxon in Latvia is not completely known.
Fig. 2. Distribution map of Salix myrtilloides L. in Latvia. O - from literature, • - herbarium
materials and personal collections.
Fig. 3. Distribution map of Satix starkeana Willd. in Latvia.
Sect. Vetrix Dumort 1825, Bijdr. Natuurk. Wetensch. 1.1 : 55.
Salix caprea L. 1753, Sp P1: 1020 J. Fisch., 1778, Vers Naturg. Livl. ; 302, sine auct.
Goat willow is a widespread species throughout Latvia. In Europe its subspecies and varieties are
not usually distinguished (Skvortsov 1981, Meikle 1984, Czerepanov 1995). In the flora of many
Central European and Baltic countries, forms are mentioned based on the form of the leaf However,
considering the ability of species morphological characteristics, the taxonomic significance of these
forms is unfounded, and was proved in the studies carried out in the dendrarium of NBG.
Salix einerea L. 1753, Sp. P1.: 1021; Grindel, 1803, Bot. Taschenb. Liv. Cur. Ehst: 290.
It is the most widespread species in Latvia. It grows in any suitable moist biotopes in forests,
meadows, river sides, it can be often found in anthropogenic biotopes - in ditches, road embankments,
roadsides, etc.
We will not mention in details the forms mentioned in the flora of the Central European and
Baltic countries due to their taxonomic insignificance. They are mostly based on the relations between
length and width of leaves, which is a very variable feature in gray willow.
Salix aurita L. 1753, Sp. Pl: 1019; J. Fisch., 1778, Vers. Naturg. Livl: 302, sine auct
This is a relatively common species in Latvia in suitable biotopes: moist edges of forests,
waterlogged meadows, etc.; disturbed areas such as ditches, roadsides and embankments (the hybrid
S. x multinervis is more common in these sites), also in bogs, edges of bogs and in different types of
moist forests. We will not consider in detail the forms mentioned in the flora of the Central European
and Baltic countries due to their taxonomic insignificance. They are mostly based on the relations
between length and width of leaves, which is a very variable feature in eared willow.
Salix starkeana Willd. 1806, Sp. Pl:
CCP, 2: 97.
4, 2: 667; Pacиньш, 1959, Ивы Лaтв. CCP, in Paст. Лaтв.
Study showed an spatially heterogeneous distribution in Latvia. This species can only be
considered as common in Vidzeme, especially in northern Vidzeme, but it can be found in frequently in
other parts of Latvia (Fig.3).
The species is often confused in herbaria with hybrids or even other species. Salix myrsinifolia that
grows in partial shaded (edges of forests, etc.) is similar to Salix starkeana, incompletely developed
Salix phylicifolia samples collected in spring can cause mistake tn identification of these species.
Sect. Arbuscella Ser. ex Duby, 1828, in D. C. Bot. Gall. 2 ed.: 426.
Salix phylicifolia L. 1753, Sp. Pl.: 1016, [p. p.: excl. var. ß]; J. Fisch., 1784, Zusatze Vers. Naturg.
Livl: 139, sine auct.
The southern border of the Salix phylicifolia distribution area crosses along the line Sigulda Rēzekne - Ludza in Latvia (Fig. 4). In the southern part of the occurrence territory it is found rarely,
only in fens and transition bogs, waterlogged edges of forests and on overgrowing river banks of water
basins. In the northern regions of Latvia and near the Estonian border, Salix phylicifolia is a common
species in suitable biotopes, and it can also be found in different disturbed biotopes along d itches, in
moist meadows, etc. in northern Estonia, e.g., in Lahema National park, this species can be found also
in biotopes such as seashore dunes.
Sect. Vimen Dumort. 1825, Bijdr. Natuurk. Wetensch. 1, 1 : 56.
Salix viminalis L. 1753, Sp. Pl.: 1021;Fischer, 1778, Vers Naturg. Livl: 302, sine auct.
The species is characterized by a wide variety of morphological characters, which explains why it
has been repeatedly suggested that the species includes several similar species. Species such as S.
gmelini Pall, and S. serotina Pall, have been proposed in the work "Flora Rossica" by P. Pallas
(Pallas 1776, 1788), but the given description is very incomplete. S. rossica defined by M. Nazarov
(Nazarov 1936) was considered to have a unique set of characters, and was accepted as a separate
species by Russian (I. Belayeva et al.) and by Estonian Salix specialists (Krall, Viljasoo 1965). After
the analysis of herbarium materials from Northern Latvia and Estonia, we concluded that distinguishing
of separate and intraspecific taxons was reasonable.
Chart 1 Characteristics of the essential morphological characters in identificaton of intraspecific taxons
of S. viminalis (modified from Krall 1962).
Salix viminalis L. var. viminalis
Western European variety. In Latvia it grows wild throughout the territory. The eastern border of
the variety in the territory of Russia is insufficiently studied.
Salix viminalis L. var. rossica (Nasarov) Evarts comb. nov.
The variety is found in the Eastern Europe and in Siberia; in Latvia this species reaches its
western border. The areas of these two common osiers varieties overlap in Latvia and Estonia and
create a complex of transition forms that are extremely difficult to identify. A. Rasi ņš in his work
named subsp. rossica as the most common species (Rasiņš 1959), Kupfer and Lakschevitz in their
herbaria determined most specimens of S. viminalis to be S. gmelinii Pall.
The distribution area of common osier in Latvia may have decreased during the last ten years, as
in suitable areas it was overgrown by the ecologically aggressive basic variety or transition forms. At
the beginning of the 20 century Seemen, during the analysis of the herbaria of Kupfer, Lakschevitz
and others noted that the distribution border of this taxon includes the Daugava valley (Seemen 19081910). However, our research showed that specimens of var. rossica corresponding (o the description
can be found mostly in north-eastern Latvia, Latgale and south-eastern Estonia. The transition forms
are found in other parts of Latvian territory.
Salix burjatica Nasarov, 1936, Фл. CCCP 5: 137, sensu Atlas Fl. Europ. 3:43.
The species resembles osier (S. viminalis), especially var. rossica, which is why it is often
confused, also in the literature. The essential features for species identification: S. burjatica has wider
leaves (up to 3.5 cm) with the wider part in the middle part of the leaf (not in the lower third as in S.
viminalis var. viminalis), the lobate margin is not well developed, and leaves are usually bright from
above (unlike S. viminalis var. rossica). Other important characters are the relative proportions of
length of style and stigma. Stigmas of S. viminalis are longer than style, but vice versa in S. burjatica
(Skvortsov 1968).
In Latvia its range is heterogeneous as the north-eastern border of its area is near. The species is
more or less common in south-eastern, south-western and central parts of Latvia, but it can be found
rarely in northern Vidzeme, and only in the south-western part of Estonia - Emajogi, Vaike - in the
valleys of Emajogi, Gauja and other rivers.
Several forms are discerned, mostly on the basis of the hairiness of leaves: f. argentata Rasiņš,
f. glabrifolia Rasiņš, f. denudata Nasarov. All of the forms have insignificant systematic importance, as
the above-mentioned differences disappear when specimens are vegetatively reproduced in the
dendrarium of the National Botanical Garden in approximately similar conditions. Specimens with
heavy hairiness f. argentea (collected near the river Bārta) do not differ from specimens of f. denudata
that grow wild near Salaspils.
Sect. Villosae Rouy, 1910, Fl. Fr. 12 : 220.
Salix lapponum . 1753, Sp. Pl.: 1019, J. Fleisch. und Em. Lindem., 1839, in J. Fleischer, Fl. Esth.,
Liv.u.Kurl.;349,
Downy willow grows in high and transition bogs, waterlogged meadows and other moist
places in Latvia. The species can only be considered as common in northern Latvia. In Daugavpils and
Liepaja districts in south-east and south-west Latvia, respectively, the species has been found only in a
few sites (Višķi, Silene, Akmeņrags, Tosmare lake, etc.), although there are biotopes asuitable for the
species also in the northern part of Latvia. The species is rare in Zemgale. (Fig.5)
Due to the decorative silvery leaves and a small compact crown Salix lapponum can be used in
parks, although the cultivation of this species is mostly limited by the ecological requirements of the
species
Sect. Daphnella Ser. ex Duby, 1828, in D. C. Bot. Gall. 2 ed.: 424.
Salix daphnoides Vill. 1789, Hist. P1. Dauphin. 3: 765, tab. 50, fig. 7; J. Fleisch. und Em. Lindem.,
1839, in J. Fleischer, Fl. Esth. Liv. Kurl.: 342, p.p
The species was introduced from Central Europe and planted in parks, along road sides, but
mostly along the seashore and on inland dunes for sand stabilization, and it can not be considered as
autochthonous. It is characterized by bright, wide, elongated leaves. Only one clone was planted. It is
often found along the sea coast of the Baltic Sea and Riga Gulf, near Daugavpils on. degraded inland
dunes, in the territory of water reservoir of the planned Daugavpils hydroelectric station, and is quite
Fig. 4. Distribution map of Salix phylicifolia L. in Latvia
Fig. 5. Distribution map of Salix lapponum L. in Latvia.
common in parks in Vidzeme and Kurzeme. This endemic Central European species grows faster and is
larger than the similar S. pomeranica that grows in the Baltic region.
S. pomeranica Willd. 1913, Enum. Hort. Berol. Suppl: 66.
The species distribution is on the south-eastern and south-western coasts of the Baltic Sea. It can be
found locally in Estonia, mostly in the south-eastern part, in the basin of Gauja river and in
Lithuania only in the western part.
The pattern of occurence of this species in Latvia is irregular. It is found along the Daugava river till
Aizkraukle and especially along the Gauja river and other smaller lower reaches of rivers flowing into
the Riga Gulf (Jūrmala, Roja, Melnsils). Several morphologically different transient forms of S.
daphnoides and S. pomeranica were found along the Riga Gulf seashore, and their occurrence has
increased over time, according to herbarium materials and personal observations It is obvious that
extensive hybridization occurs in that area, and it is not possible to classify these spec imens. The
number of these hybrido samples greatly increases in places with increased antropogenic impact. It is
obvious that the normal species cross-pollination is hindered, as the expansive S. daphnoides has
hybridized in these biotopes. Salix pomeranica requires special protection measures, and it should be
included in the list of particularly protected plants.
Salix pomeranica has not been found as wild species in western Latvia, but can be found planted in
some localities in Vidzeme, Zemgale and Kurzeme (Fig. 6).
Salix acutifolia Willd. 1806, Sp. Pl. 4,2 : 668; J. Fleisch. und Em. Lindem., 1839, in J. Fleischer., Fl.
Esth. Liv Kurl. : 341
Salix acutifolia is often cultivated throughout Latvia, especially vegetatively reproduced male
specimens for willow buds at Easter; it is often planted with S. daphnoides on dunes, sandy river edges,
along roads, etc., to stabilize sandy soils. In some locations the species has become wild and produces
natural hybrids with S. daphnoides and S. pomeranica. These hybrids can often be found in synantropic
biotopes, and their determination is very difficult.
The distribution of the species is very unclear. This was already stated by Rasiņš (1958), who
reported on the main studies of the species occurrence and the morphological borders of the Daphnella
section. In Lithuania (Smaliukas 1996, 1997), Byelorussia (Parfenov, Mazin 1986) and Estonia (Krall,
Viljasoo 1956,1971) the species is most probably wild. In most of the area, .S. acutifolia is often found
together with Populus alba and Salix alba. This plant communities with Salix dominant is also found in
south-eastern Latvia, in the Daugava valley from Piedruja till Krāslava and in the territory of the nature
park "Daugavas loki". The microclimate of the Daugava valley in this area has ensured the preservation
of many Central European plants and animals species far from the northern border of their main range,
including Populus alba and Salix acutifolia. The autochthonous individuals are only found in eastern
Latvia, outside the Daugava valley in some places in Balvi, Gulbene and Ludza districts (Fig. 7).
Fig. 6. Distribution map of Salix pomeranica Willd. In Latvia.
Fig. 7. Distribution map of Salix acutifolia Vill. in Latvia. ▲ -allochthonous, • -autochthonous.
Sect. Incubaceae A. Kerner, 1860, Verh. Zool - Bot. Ges. Wien, 10: 264.
Salix repens L. 1753, Sp. Pl.: 1020, J. Fisch., 1778, Vers. Naturg. Livl.; 302, sine auct., p.p.
Creeping willow is very rare and found in the districts of Liepāja and Ventspils, in a narrow zone at
the seashore. There is little proof about the occurrence of this species in the country in the previous
collections, which is why creeping willow is not included in the list of protected species. All known
herbarium samples were S. rosmarinifolia or hybrids between these two species, including Latvian
samples from A. Rasiņš herbarium. This situation arose mostly due to the fact that in many work
published in Latvia, S. repens was integrated with S. rosmarinifolia and distinguished only as variety
S. repens var. repens, but natural scientists did not pay attention to most of varieties.
In our study it was found for the first time in 1997 in Liepāja district between Tosmare Lake and the
sea on the sandy embankments and on the dunes near Šķēde (Medzes pagasts). Later it was found also
in Ziemupe, in several areas in Ventspils district on dimes, moist slacks between dunes, etc. Herbaria
specimens are stared in the Department of Dendroflora of the NBG. Several S. repens herbaria
collected by other botanists are located in the herbarium of Department of Botany, LU Institute of
Biology (LATV). An undefined herbarium in RIG II collected by A. Zāmelis in 1925 near Ziemupe
(No. 4250) proved to be S. repens.
In Northern Europe, including the Estonian islands, S. repens var. arenaria (L.) Anderss grows
wild with wide ovoid, bilaterally dense silvery hairy leaves. S. repens is often cultivated with the name
"Nitida". This variety may possibly be found also in suitable biotopes in the districts of Ventspils and
Liepāja.
Salix rosmarinifolia L. 1753, Sp. Pl.: 1020; J. Fisch., 1784, Zusatze Vers. Naturg. Livl. :139, sine
auct..
The species is widespread throughout Latvia; it grows on raised and transition bogs, waterlogged
meadows and on lake shores. It can also be found in dry habitats - on sandy dunes and embankments;
these specimens usually have smaller leaves and bright silvery hairiness.
The areas of two similar species - S. rosmarinifolia and S. repens in the Eastern Europe overlap,
including in the western part of Latvia. Wide hybridization of these species occurs in this zone, which
is why the morphological features of both taxons are unclear.
Sectio Helix Dumort. 1825, Bijdr. Natuurk Wetensch 1,1: 56.
Salix purpurea L.1753, Sp. Pl.: 1017, Friebe, 1805, Fl. Liefl. Ehst. Kurl: 335.
The Western European species in Latvia are located near the northern -eastern border of their area,
but they are frequent, including in zones near the Pskov district, Russia, and Braslav district,
Byelorussia. We can conclude that the species gradually is expanding in the eastern direction and it
grows mostly in disturbed biotopes (roadsides, embankments, gravel pits, etc.). It is rarely found in
biotopes typical for this species - rivers and lake sides, moist meadows and flood-plains. It obviously
that it can not compete with the ecologically more aggressive S. viminalis and .V triandra
Purple willow is often found planted (to produce quality shoots), also outside of the natural area
(Estonia, etc.). It has become wild in some places, which causes problems in die determination of
natural borders of species occurrence.
In Latvia, two decorative forms have naturalized in plantations:
"Lambertiana" - purple-red shoots, ovoid, acute leaves, shorter and wider than the basic
species, opposite Die length of shoots.
"Pendula" - large shrub, often taller than 2 m with long, thin and pendulous shoots.
6. Hybridization in willow genus
Regarding reciprocal hybridization of Salix genus species two different points of view exist: many
dendrologists from Western Europe believe that hybrids are common (Rechinger 1981, 1992; Meikle
1984), several Latvian botanists consider them as usual (Lehmann 1895, Stares 1925, Galenieks 1955) In
contrast, representatives of the dendrology school of the former USSR - A. Skvortsov (Skvortsov
1968,1981), M. Nazarov (Nazarov 1936), L. Pravdin (Pravdin 1951) and others consider that the
hybridization in Salix genus was a rare event, and they distinguished specimens with features of two
species as plants of one or the other species, explaining the variability with extreme polymorphism of
willow species.
When a sample slightly differs from the species description, decision between identification as a
hybrid or as "pure" species, cannot be made unambiguously. We do not consider hybridization
occurred only using one or two characteristics (especially if these are generative organ characters). The
complex of features must be considered to make a conclusion if the sample is "pure" species or hybrid.
Triple or even quaternary hybrids are sometimes mentioned in publications or on herbarium labels,
including in Latvia, e.g., S. cinerea x caprea x phylicifolia, S. cinerea x myrtilloides x starkeana, S.
cinerea x purpurea x viminalis, S. aurita x myrtillodes x starkeana and 10 others (Stares 1925, Rasiņš
1958). We consider that the origin of these hybrids in the wild is unlikely (there is no evidence about the
fertility of the first generation), and the objective determination of these triple and sometimes
quaternary hybrids is also unlikely, which is why they are not mentioned in our work.
Different numbers of hybrids have been reported by different authors. Rasiņš indicated 55 hybrid
species in Latvia (Rasiņš 1958), Cinovskis - 56 (Cinovskis et al. 1993). Not all species are equally
distributed in Latvia. For example, in the Daugavpils district only 25 hybrids were found. Only three
hybrids can be considered as more or less wide-spread: S. x rubens, S. x multinervis and S. x rubra and
S. acutifolia x S. daphnoides, which are often cultivated and have became wild in some places. Other
hybrids were found rarely or very rarely. Hybrids compose 1-2 % of the total amount of willow
specimens in natural communities, but in disturbed, antropogenic areas hybrids total approximately 5 %
of the willow plants.
In our study in the territory of Latvia we found 68 hydrid species and only a few of them can be
considered as wide-spread. Other taxons should be considered as rare or very rare.
• Wide-spread hybrids, frequent in some localities, found in more than 50 sites: S. x rubens
Schrank (S. alba x fragilis), S. x sepulcralis Simonk.’Chrysocoma’ (S. alba "Vitellina" x S.
babylonica) (only in cultivation, does not become wild), S. x multinervis Doell (S. aurita x S.
cinerea), S. x rubra Huds. (S. viminalis x S. purpurea), S. acutifolia x S. daphnoides
'Paschal'.
• Hybrids that were found quite often, found in 30-50 sites: S. x mollissima Ehrh. (S. triandra x
S. viminalis), S. x ehrhartiana Sm. (S. alba x S. pentandra), S. x rugulosa Anderss. (S. aurita
x S. myrtilloides), S. x vaudensis Schleich. (S. cinerea x S. myrsmifolia), S. x tetrapla J.
Walker (S. myrsinifolia x phylicifolia), S. x polymorpha Host (S. caprea x S. cinerea), S. x
coerulescens Doell (S. cinerea x starkeana), S. cinerea x phylicifolia, S. x holosericea Willd.
(S. cinerea x S. viminalis), S. x livescens Doell (S. aurita x S. starkeana), S. daphnoides x
pomeranica.
Rarely hybrids, found in 10-30 sites, S. x schumanniana Seem. (S. triandra xpentandra), S. x
undulata Ehrh. (S. alba x S. triandra), S. x meyeriana Rostk. ex Willd. (S. fragilis x
pentandra), S. x pendulina Wender. 'Blanda' (S. fragilis a S. babylonica) (only in cultivation,
does not become wild), S. x versifolia Wahlenb. (S. myrtilloides x lapponum), S. x cvriacea
Scleich. (S, aurita x S. myrsinifolia), S. x myrtoides Doell (S. myrsinifolia x starkeana),
S. myrsinifolia x S. rosmarinifolia, S. x capreola J. Kern. (S. aurita x S. caprea), S. x laurina
Sm. (S. caprea x phylicifolia), S. x smithiana Willd. (S. caprea x viminalis), S. x compacta
Anderss. (S. aurita x S. lapponum), S. x ambigua Ehrh. (S. aurita x S. rosmarinifolia), S.
viminalis x rosmariniolia, S. acutifolia x pomeranica S. repens x rosmarinifolia, S. x
doniana Smith (V. rosmarinifolia x purpurea).
Very rarely hybrids, known in 1 up to 10 sites: S. x ahpecuroides Tmisch. {S. fragilis x S.
triandra), S. myrtilloides x starkeana, S. myrtilloides x phylicifolia, S. myrtilloides x
myrsinifolia, S. myrtilloides x rosmarinifolia, S. x latifolia Forbes (S. myrsinifolia x caprea),
S. myrsinifolia x burjatica, S. myrsinifolia x viminalis, Salix x beckeana Beck
(S. myrsinifolia x purpurea), S. caprea x S. burjatica, S. caprea x pomeranica, S. caprea x
starkeana, S. x canescens Fries (S. caprea x lapponum), S. cinerea x S. burjatica, S. cinerea x
lapponum, S. x pontederana Willd. (S. cinerea x purpurea}, S. cinerea x rosmarinifolia,
S. aurita x phylicifolia, S. x dichroa Doell (S. aurita x purpurea), S. x fruticosa Doell
(S. aurita x viminalis), S. aurita x repens, S. starkeana x phylicifolia, S. starkeana x
rosmarinifolia t S. starkeana x viminalis, S. phylicifolia x burjatica, S. phylicifolia x
viminalis, S. viminalis x S. burjatica, S. x digenea Kerner (S. viminalis x daphnoides),
S. burjatica x purpurea, S. burjatica x lapponum, S. lapponum x purpurea, S. lapponum x
rosmarinifolia, S. x calliantha J. Kern. (S. daphnoides x purpurea), S. daphnoides x
rosmarinifolia, S. acutifolia x purpurea.
Conclusions
Willow (Salix L.) is the biggest genus in the Latvian dendroflora. In total, 20 willow species and 68
hybrids were found. For the first time in Latvia, sites with S. repens was found. S. pomeranica was
distinguished as an independent species in Latvia, a new taxon S. viminalis var. rossica was
distinguished. We also determined die distribution of other willow species in Latvia and in the Baltic
region in general.
Distribution and autochthonism of species
Of the 20 wild Salix species found in Latvia two - S. fragilis and S. daphnoides - can be
considered as allochthonous that became wild. The other 18 species are autochthonous elements of the
Latvian flora. After they became wide-spread these willow species can be divided into the following
spatial groups:
S. pomeranica is an endemous plant from the eastern Baltic region, which in Latvia can be found in
the wild and only in the Gauja valley and along the seashore of Riga Gulf.
S. cinerea, S. lapponum, S. myrsinifolia, S. pentandra, S. phylicifolia and S. alba are European and
Western Siberian species. S. alba can be found wild only in the valleys of big rivers, in other areas the
species is widely cultivated in plantations. This has caused many disputes and misunderstandings
regarding Latvian autochthonous dendroflora
S. burjatica, S. caprea, S. myrtilloides, S. starkeana, S. triandra, S. rosmarinifolia, S. viminalis are
Eurasian species.
S. aurita, S. purpurea, S. repens and S. acutifolia are European species. S. acutifolia in Latvia are
found wild only in Latgale, mostly in suitable natural biotopes in the valley of the Daugava.
Morphological borders of taxa
Species of the willow genus are characterized by morphological plasticity. Morphological features
within species differ between biotopes very significantly, especially in the leaf length, its width and
hairiness. In species identification as many characteristics as possible should be used, as usually one
specific character can not be found across all specimens of the taxon. Among the characteristics
incorporated in a unified system, the most efficient must be chosen for each specific sample in a given
situation. For this reason it is complicated or even impossible to use some identification keys, even
those published in Latvia, for species identification, especially without experience. It is possibl e to
identify herbarium specimens collected at the beginning of vegetation season (with catkins) or from
uncharacteristic shoots (sprouts, branches growing in the shade) only in some cases.
However, groups of some characteristics vary relatively insignificantly and can be used for
identification of sections or species:
• Colour of bark of young shoots, often also hairiness, wax coat for the species Daphnella.
• Structure of wood surface, prominent longitudinal striae for species of the section Vetrix.
• Colour of buds, their form, and arrangement of vegetative and generative buds on shoot.
• Proportions of length to width of leaves, the widest part of the leaf blade, margin of the leaf
blade.
• Stipules, their forms, level of preservation during the period of vegetation.
• Time of flowering (before, simultaneously, after opening of leaves).
• Form of fruit (capsule), its colour, and hairiness, in the section Incubaceae.
Intraspecific taxons
The Salix genus is characterized by extremely wide phenotypic variability, which is why many
forms have been previously distinguished. When vegetatively reproduced plants were grown in the
same ecological conditions in the dendrarium of the National Botanical Garden, it was shown that the
wariability of forms disappeared in the most cases. Forms that had been mentioned previously in the
most studies in the Baltic States proved to be taxonomically insignificant. Distinguishing the
intraspecific taxons was reasonable only for a few willow species - S. triandra (f. concolar,
f. discolor), S. myrsinifolia (var. lithuanica), S. viminalis (var. rossica). S. fragilis in Latvia is
represented mostly as separate clones.
Rare species
Two willow genus species were included in previous lists of protected species - S. phylicifolia
and S. myrtilloides. The necessity for protection of these species was also shown by our study
Although in the northern Vidzeme and northern Latvia both species are often found in suitable
biotopes, an important threat is the decrease of habitat, such as transient bo gs, moist meadows and
forests. Three more species are considered as rare: S. acutifolia, S. pomeranica and S. repens. The
distribution of S. repens in Latvia is on the eastern border of its range. S. acutifolia in Latvia falls on the
western part of its distribution. S. pomeranica is particularly threatened by genetic erosion, as it
massively cross-pollinates with the close related S. daphnoides. Therefore, it is particularly important
maintain the species in its natural biotopes and to prevent the use of close relative foreign species in
plantations, at least in the territory of the Gauja valley.
Hybridization
In the study we found 68 hybrid species in the territory of Latvia. Hybrids compose 1-2 % of the
total number of willow specimens in natural habitats, but the number of hybrids in disturbed,
antropogenic communities increases dramatically - approximately 5 % of the total number of willow
plants. Only five hybrids are considered as common: S. x rubens, S. x sepulcralis
Simonk.'Chrysocoma' (often cultivated, does not become wild), S. x multinervis and S. acutifolia x S.
daphnoides 'Paschal'. In 30-53 sites ten other hybrids were found: S. x mollissima, S. x ehrhartina, S.
x rugulosa, S. x vaudensis, S. x tetrapla, S. x polymorpha, S. x coerulescens, S. cinerea x phylicifolia,
S. x holosericea, S. x livescens. Other hybrids are rarely found in Latvia, mostly only in a few sites.
Publikācijas
Publications
Evarts-Bunders Pēteris. 2005. Vītolu (Salix L.) ģints Latvijā. Monogrāfija. -Daugavpils, 107. lpp
Bice M., Evarts-Bunders P., Knape Dz., Šmite D., Bondare I. 2005. Ogres rajona dendroloģisko
stādījumu koki un krūmi. -In: Latvijas veģetācija. - Rīga, 9,33 - 56.
Bice M, Evarts-Bunders P., Knape Dz., Šmite D. 2005. Preiļu rajona dendroloģisko stādījumu koki
un krūmi. -In: Latvijas veģetācija. -Rīga, 9, 57-69.
Bice M, Evarts-Bunders P., Knape Dz., Šmite D. 2005. Rēzeknes rajona dendroloģisko stādījumu
koki un krūmi, -In: Latvijas veģetācija. - Rīga, 9, 70-88.
Bice M., Knape Dz. Šmite D., Evarts-Bunders P. 2004. Aizkraukles rajonā konstatētie koki un
krūmi. -In: Latvijas veģetācija. -Rīga, 8, 7 - 35
Bice M., Knape Dz., Šmite D., Evarts-Bunders P. 2004. Ludzas rajonā konstatētie koki un krūmi -In:
Latvijas veģetācija. - Rīga, 8,85-101.
Evarts-Bunders Pēteris. 2004. Willows (Salix L.) of Vimen Dumort section in Latvia. -In: Acta
Biologica Universitatis Daugavpiliensis. -Daugavpils, 4 (1), 11-18.
Evarts-Bunders Pēteris. 2003. Willows (Salix L.) of Daphnella Ser. ex Duby section in Latvia. -In:
Acta Biologica Universitatis Daugavpiliensis. -Daugavpils, 3 (1), 25-32
Эвартс-Бундерс Петерис. 2003. Ива филиколистная (Salix рhуlicifolia L.): проблемы
распространения и гибридизации в Латвии. -Одесса: ОНУ, Тезисы докладов международной
научной конференции Биоразнобразие, экология, эволюция, адаптация',
Evarts-Bunders Pēteris. 2002 Vaskulārie augi. In: A. Barševskis, N. Savenkovs, P. Evarts-Bunders et
al. Silenes dabas parka fauna, flora un veģetācija. -Daugavpils: BKI, lpp 8-21.
Evarts-Bunders P. 2001. Some rare and unclear Willow (Salix L.) species in Latvia. Acta Biologica
Universitatis Daugavpiliensis. -Daugavpils, 1(2): 103-106.
Evarts-Bunders P. 2001. Vītolu (Salix L.) ģints pētījumi Latgalē. -In: Ada Latgalica. -Daugavpils: LPI izd.
11: 421-438.
Эвартс-Буидерс П 1999. Наиболее распространенные и перспективные сорта ив в Латвии.
Тезисы международной конференции "Проблемы дендрологии на рубеже ХХI века", Москва,
ГБС РАН.
Evarts-Bunders P. 1999. Dabas parka "Daugavas loki" dendrofloras apskats. -Daugavpils: Saule,
LPI 8. konferences referātu tēžu krājums. lpp 53-54
Evarts-Bunders P., Bice M. 1999. The monumental trees of Daugavpils district. In; Plant genefund
accumulation, evaluation and protection in the botanical gardens. Vilnius, p.25-28.
Эвартс-Будерс П. 1998. Распространение, систематика и экология ив (Sаliх L.) в
Даугаувпилсском районе. -Ялта: ГНБС, Материалы международной конференции "Проблемы
дендрологии, цветоводства и плодоводства".
Evarts-Bunders P. 1996. Vītola (Salix L) ģints sistemātika, ekoloģija un izplatība Daugavpils
rajonā. In: Dabīgo ūdens resursu aizsardzības problēmas Daugavpilī. -Daugavpils. 19-25 lpp.
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