''Betula pubescens'' (syn. ''Betula alba''), commonly known as downy birch and also as moor birch, white birch, European white birch or hairy birch, is a species of

deciduous In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed Leaf, leaves, usually in the autumn; to the shedding of petals, aft ...

tree, native and abundant throughout northern

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

and northern

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

, growing further north than any other broadleaf tree. It is closely related to, and often confused with, the

silver birch ''Betula pendula'', commonly known as silver birch, warty birch, European white birch, or East Asian white birch, is a species of tree in the family Betulaceae, native to Europe and parts of Asia, though in southern Europe, it is only found ...

(''B. pendula''), but grows in wetter places with heavier soils and poorer drainage; smaller trees can also be confused with the dwarf birch (''B. nana''). Six varieties are recognised and it hybridises with the silver and dwarf birches. A number of cultivars have been developed, but many are no longer in cultivation. The larva of the autumnal moth (''Epirrita autumnata'') feeds on the foliage and in some years, large areas of birch forest can be defoliated by this insect. Many fungi are associated with the tree and certain pathogenic fungi are the causal agents of birch dieback disease. The tree is a

pioneer species Pioneer species are resilient species that are the first to colonize barren environments, or to repopulate disrupted biodiverse steady-state ecosystems as part of ecological succession. Various kinds of events can create good conditions for pi ...

, readily colonising cleared land, but later being replaced by taller, more long-lived species. The bark can be stripped off without killing the tree. The bark and the timber is used for turnery and in the manufacture of plywood, furniture, shelves, coffins, matches, toys and

wood flooring Wood flooring is any product manufactured from timber that is designed for use as flooring, either structural or aesthetic. Wood is a common choice as a flooring material and can come in various styles, colors, cuts, and species. Bamboo floorin ...

. The inner bark is edible and it was ground up and used in bread-making in times of

famine A famine is a widespread scarcity of food caused by several possible factors, including, but not limited to war, natural disasters, crop failure, widespread poverty, an Financial crisis, economic catastrophe or government policies. This phenom ...

. The rising sap in spring can be used to make refreshing drinks, wines, ales and liqueurs and various parts of the tree have been used in

herbal medicine Herbal medicine (also called herbalism, phytomedicine or phytotherapy) is the study of pharmacognosy and the use of medicinal plants, which are a basis of traditional medicine. Scientific evidence for the effectiveness of many herbal treatments ...

Description

''Betula pubescens'' is known as downy birch, with other common names including moor birch, white birch, European white birch or hairy birch. It is a

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...

growing to tall (rarely to 27 m), with a slender crown and a trunk up to (exceptionally 1 m) in diameter, with smooth but dull grey-white

bark Bark may refer to: Common meanings * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Arts and entertainment * ''Bark'' (Jefferson Airplane album), ...

finely marked with dark horizontal

lenticel A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the Bark (botany), bark of woody stems and roots of gymnosperms and dicotyledonous flowering plants. It func ...

s. The shoots are grey-brown with fine downy. The

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

are ovate-acute, long and broad, with a finely serrated margin. The

flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...

s are wind-pollinated

catkin A catkin or ament is a slim, cylindrical flower cluster (a spike), with inconspicuous or no petals, usually wind- pollinated ( anemophilous) but sometimes insect-pollinated (as in '' Salix''). It contains many, usually unisexual flowers, arra ...

s, produced in early spring before the leaves. The

fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

is a pendulous, cylindrical aggregate long and wide which disintegrates at maturity, releasing the individual seeds; these seeds are long with two small wings along the side.

Species identification

''B. pubescens'' is closely related to, and often confused with, the

(''B. pendula''). Many

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

n texts treat the two species as

conspecific Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organism ...

(and cause confusion by combining the downy birch's alternative vernacular name, white birch, with the scientific name ''B. pendula'' of the other species), but they are regarded as distinct species throughout Europe. Downy birch can be distinguished from silver birch with its smooth, downy shoots, which are hairless and warty in silver birch. The bark of the downy birch is a dull greyish white, whereas the silver birch has striking white, papery bark with black fissures. The leaf margins also differ, finely serrated in downy birch, coarsely double-toothed in silver birch. The two have differences in

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

requirements, with downy birch more common on wet, poorly drained sites, such as clays and peat bogs, and silver birch found mainly on dry, sandy soils. In more northerly locations, downy birch can also be confused with the dwarf birch (''Betula nana''), both species being morphologically variable. All three species can be distinguished cytologically, silver birch and dwarf birch being

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, ...

(with two sets of chromosomes), whereas downy birch is

tetraploid Polyploidy is a condition in which the cells of an organism have more than two paired sets of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two complete sets of chromosomes, one fro ...

(with four sets of chromosomes). In Iceland, dwarf birch and downy birch sometimes hybridise, the resulting plants being

triploid Polyploidy is a condition in which the cells of an organism have more than two paired sets of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two complete sets of chromosomes, one fro ...

(with three sets of chromosomes).

Distribution and habitat

''Betula pubescens'' has a wide distribution in northern and central Europe and Asia. Its range extends from Newfoundland, Iceland, the British Isles and Spain eastwards across northern and central Europe and Asia as far as the

Lake Baikal Lake Baikal is a rift lake and the deepest lake in the world. It is situated in southern Siberia, Russia between the Federal subjects of Russia, federal subjects of Irkutsk Oblast, Irkutsk Oblasts of Russia, Oblast to the northwest and the Repu ...

region in Siberia. The range extends southwards to about 40°N, its southernmost limit being Turkey, the

Caucasus The Caucasus () or Caucasia (), is a region spanning Eastern Europe and Western Asia. It is situated between the Black Sea and the Caspian Sea, comprising parts of Southern Russia, Georgia, Armenia, and Azerbaijan. The Caucasus Mountains, i ...

and the

Altai Mountains The Altai Mountains (), also spelled Altay Mountains, are a mountain range in Central Asia, Central and East Asia, where Russia, China, Mongolia, and Kazakhstan converge, and where the rivers Irtysh and Ob River, Ob have their headwaters. The ...

. It is a

which establishes itself readily in new areas away from the parent tree. This allows other woodland trees to become established and the birch, a short-lived tree, eventually gets crowded out as its seedlings are intolerant of shady conditions. Downy birch extends further north into the

Arctic The Arctic (; . ) is the polar regions of Earth, polar region of Earth that surrounds the North Pole, lying within the Arctic Circle. The Arctic region, from the IERS Reference Meridian travelling east, consists of parts of northern Norway ( ...

than any other broadleaf tree. Specimens of the subarctic populations are usually small and very contorted, and are often distinguished as arctic downy birch or mountain birch, ''B. p.'' var. ''pumila''. (not to be confused with '' B. nana''). This variety is notable as being one of very few trees native to

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

and

Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

, and is the only tree to form woodland in Iceland. At one time the island is thought to have been covered in downy birch woodland, but that cover is reduced to about one percent of the land surface today.

Varieties and cultivars

Three varieties are recognised, the nominate ''Betula pubescens'' var. ''pubescens'', ''B. p.'' var. ''litwinowii'' (distributed in the

and

Turkey Turkey, officially the Republic of Türkiye, is a country mainly located in Anatolia in West Asia, with a relatively small part called East Thrace in Southeast Europe. It borders the Black Sea to the north; Georgia (country), Georgia, Armen ...

) and ''B. p.'' var. ''pumila'' (arctic downy birch or mountain birch, formerly called ''B. p.'' subsp. ''tortuosa''). The latter has arisen from the hybridization of var. ''pubescens'' and ''B. nana'' (dwarf birch) and is characterised by its shrubby habit, smaller leaves, resinous glands and the smaller wings on the fruit. A number of cultivars have been grown, but many are no longer in cultivation. They include "Armenian gold", "Arnold Brembo" (scented foliage), ''crenata nana'' (shrubby and dwarf), ''incisa'' (lobed foliage), ''integrifolia'' (unlobed foliage), ''murigthii'' (shrubby with doubly serrate leaves), ''ponitica'' (hairless), ''undulata'' (leaf margins waxy), ''urticifolia'' (nettle-leaved), ''variegata'' (variegated) and "Yellow wings". Two others, described by the German botanist Ernst Schelle in 1903, are also lost; '' pendula'', a cultivar with a leader and weeping branches, and '' pendula nana'', which grows into an umbrella-shaped tree with weeping branches, but no leader. ''Betula pubescens'' 'Rubra' has maroon foliage.

Ecology

The larva of the autumnal moth (''Epirrita autumnata'') feeds on the foliage of ''Betula pubescens'' and other tree species. In outbreak years, large areas of birch forest can be defoliated by this insect. Damage to the leaf tissue stimulates the tree to produce chemicals that reduce foliage quality, stunting the growth of the larvae and reducing their pupal weights. In Greenland, about seventy species of

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

have been found growing in association with ''B. pubescens'', as

parasites Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The en ...

or saprobes on living or dead wood. Some of the most common fungi include '' Ceriporia reticulata'', ''

Chondrostereum purpureum ''Chondrostereum purpureum'' is a fungal plant pathogen which causes silver leaf disease of trees. It attacks most species of the rose family Rosaceae, particularly the genus ''Prunus''. The disease is progressive and often fatal. The common name ...

'', '' Exidia repanda'', '' Hyphoderma'' spp, ''

Inonotus obliquus ''Inonotus'' is a genus of fungi in the family Hymenochaetaceae. The genus, described by Petter Karsten Petter Adolf Karsten (16 February 1834 – 22 March 1917) was a Finnish mycologist, the foremost expert on the fungi of Finland in his da ...

'', '' Inonotus radiatus'', '' Mycena galericulata'', '' Mycena rubromarginata'', '' Panellus ringens'', '' Peniophora incarnata'', ''

Phellinus lundellii ''Phellinus lundellii'' is a species of fungus belonging to the family Hymenochaetaceae The ''Hymenochaetaceae'' are a family (biology), family of fungi in the order Hymenochaetales. The family contains several species that are implicated in ...

'', '' Radulomyces confluens'', '' Stereum rugosum'', '' Trechispora'' spp., '' Tubulicrinis'' spp. and '' Tyromyces chioneus''. Birch dieback disease, associated with the fungal pathogens '' Marssonina betulae'' and '' Anisogramma virgultorum'', can affect planted trees, while naturally regenerated trees seem less susceptible. This disease also affects ''Betula pendula'' and in 2000 was reported at many of the sites planted with birch in Scotland during the 1990s.

Uses

The outer layer of bark can be stripped off the tree without killing it and can be used to make

canoe A canoe is a lightweight, narrow watercraft, water vessel, typically pointed at both ends and open on top, propelled by one or more seated or kneeling paddlers facing the direction of travel and using paddles. In British English, the term ' ...

skins, drinking vessels and roofing tiles. The inner bark can be used for the production of

rope A rope is a group of yarns, Plying, plies, fibres, or strands that are plying, twisted or braided together into a larger and stronger form. Ropes have high tensile strength and can be used for dragging and lifting. Rope is thicker and stronger ...

and for making a form of oiled paper. This bark is also rich in

tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and Precipitation (chemistry), precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' is widel ...

and has been used as a brown dye and as a preservative. The bark can also be turned into a high quality

charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, ca ...

favoured by artists. The twigs and young branches are very flexible and make good

whisk A whisk is a cooking utensil which can be used to blend ingredients smooth or to incorporate air into a mixture, in a process known as '':wikt:whisk, whisking'' or '':wikt:whipping, whipping''. Most whisks consist of a long, narrow handle with ...

s and

broom A broom (also known as a broomstick) is a cleaning tool, consisting of usually stiff fibers (often made of materials such as plastic, hair, or corn husks) attached to, and roughly parallel to, a cylindrical handle, the broomstick. It is thus a ...

s. The timber is pale in colour with a fine, uniform texture and is used in the manufacture of plywood, furniture, shelves, coffins, matches and toys, and in turnery. The

Sami people Acronyms * SAMI, ''Synchronized Accessible Media Interchange'', a closed-captioning format developed by Microsoft * Saudi Arabian Military Industries, a government-owned defence company * South African Malaria Initiative, a virtual expertise ...

of Scandinavia used the bark of both ''B. pubescens'' and ''B. pendula'' as an ingredient in bread-making; the reddish

phloem Phloem (, ) is the living tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This transport process is ...

, just below the outer bark, was dried, ground up and blended with wheat flour to make a traditional loaf. In

Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...

mämmi Mämmi (; ) is a traditional Finnish dessert, eaten around Easter. Mämmi is traditionally made of water, rye flour, ground malted rye, salt, and dried, ground Seville orange zest. The mixture is then left to sweeten naturally, before b ...

, a traditional Easter food, was packed and baked in boxes of birch bark. Nowadays, cardboard boxes are used, but imprinted with the typical bark pattern. Birch bark was used as an emergency food in times of famine; in

Novgorod Veliky Novgorod ( ; , ; ), also known simply as Novgorod (), is the largest city and administrative centre of Novgorod Oblast, Russia. It is one of the oldest cities in Russia, being first mentioned in the 9th century. The city lies along the V ...

in 1127–28, desperate people ate it along with such things as the leaves of lime trees, wood pulp, straw, husks and moss. In Iceland, trimmings of birch trees are used with birch sap in the making of a sweet birch liqueur. The removal of bark was at one time so widespread that

Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

expressed his concern for the survival of the woodlands. The leaves can be infused with boiling water to make a tea, and extracts of the plant have been used as herbal remedies. Both ''B. pubescens'' and ''B. pendula'' can be tapped in spring to obtain a sugary fluid. This can be consumed fresh, concentrated into a syrup similar to the better-known

maple syrup Maple syrup is a sweet syrup made from the sap of maple trees. In cold climates, these trees store starch in their trunks and roots before winter; the starch is then converted to sugar that rises in the sap in late winter and early spring. Ma ...

, or can be fermented into an ale or wine. In Scandinavia and Finland, this is done on a domestic scale, but in the former USSR, particularly Russia, Ukraine, Belarus, Estonia, Latvia and Lithuania, birch sap is harvested commercially and used to manufacture cosmetics, medicines and foodstuffs.

References

External links

''Betula pubescens''
- information, genetic conservation units and related resources.

European Forest Genetic Resources Programme European Forest Genetic Resources Programme (EUFORGEN) is an international network that promotes the conservation and sustainable use of forest genetic resources in Europe as an integral part of sustainable forest management. It was established ...

(EUFORGEN) * * {{Authority control pubescens Flora of Europe Flora of Greenland Flora of Iceland Flora of the Caucasus Flora of Siberia Plants described in 1791 Trees of Europe Trees of continental subarctic climate Trees of subpolar oceanic climate Garden plants of Europe Ornamental trees Taxa named by Jakob Friedrich Ehrhart