Betula pendula, commonly known as silver birch, warty birch, European white birch,[2] or East Asian white birch,[3] is a species of tree in the familyBetulaceae, native to Europe and parts of Asia, though in southern Europe, it is only found at higher altitudes. Its range extends into Siberia, China, and southwest Asia in the mountains of northern Turkey, the Caucasus, and northern Iran. It has been introduced into North America, where it is known as the European white birch or weeping birch[4] and is considered invasive in some states in the United States and parts of Canada. The tree can also be found in more temperate regions of Australia.[citation needed]
The silver birch is a medium-sized deciduous tree that owes its common name to the white peeling bark on the trunk. The twigs are slender and often pendulous and the leaves are roughly triangular with doubly serrate margins and turn yellow and brown in autumn before they fall. The flowers are catkins and the light, winged seeds get widely scattered by the wind. The silver birch is a hardy tree, a pioneer species, and one of the first trees to appear on bare or fire-swept land. Many species of birds and animals are found in birch woodland, the tree supports a wide range of insects and the light shade it casts allows shrubby and other plants to grow beneath its canopy. It is planted decoratively in parks and gardens and is used for forest products such as joinery timber, firewood, tanning, racecourse jumps, and brooms. Various parts of the tree are used in traditional medicine and the bark contains triterpenes, which have been shown to have medicinal properties.
Description
Silver birchSilver birch has often pendulous twigs, after which the tree has received its scientific name.
The silver birch typically reaches 15 to 25m (49 to 82ft) tall (exceptionally up to 31m (102ft)),[5] with a slender trunk usually under 40cm (16in) diameter. The bark on the trunk and branches is golden-brown at first, but later this turns to white as a result of papery tissue developing on the surface and peeling off in flakes, in a similar manner to the closely related paper birch (B. papyrifera). The bark remains smooth until the tree gets quite large, but in older trees, the bark thickens, becoming irregular, dark, and rugged. Young branches have whitish resin warts and the twigs are slender, hairless, and often pendulous. The buds are small and sticky, and development is sympodial – the terminal bud dies away and growth continues from a lateral bud. The species is monoecious with male and female catkins found on the same tree.[6] Some shoots are long and bear the male catkins at the tip, while others are short and bear female catkins. The immature male catkins are present during the winter, but the female catkins develop in the spring, soon after the leaves unfurl.[5]
The leaves have short, slender stalks and are 3 to 7cm (1.2 to 2.8in) long, triangular with broad, untoothed, wedge-shaped bases, slender pointed tips, and coarsely double-toothed, serrated margins. They are sticky with resin at first, but this dries as they age, leaving small, white scales. The foliage is a pale to medium green and turns yellow early in the autumn before the leaves fall. In midsummer, the female catkins mature and the male catkins expand and release pollen, and wind pollination takes place. A catkin of Silver birch could produce an average of 1.66 million pollen grains.[7] The small, 1- to 2-mm winged seeds ripen in late summer on pendulous, cylindrical catkins 2 to 4cm (0.8 to 1.6in) long and 7mm (0.3in) broad. The seeds are very numerous and are separated by scales, and when ripe, the whole catkin disintegrates and the seeds are spread widely by the wind.[5][8]
Silver birch can easily be confused with the similar downy birch (Betula pubescens). Yet, downy birches are characterised by hairy leaves and young shoots, whereas the same parts on silver birch are hairless. The leaf base of silver birch is usually a right angle to the stalk, while for downy birches, it is rounded. In terms of genetic structure, the trees are quite different, but do, however, occasionally hybridize.[6]
Distribution and habitat
The silver birch grows naturally from western Europe eastwards to Kazakhstan, the Sakha Republic in Siberia, Mongolia, and the Xinjiang province in China, and southwards to the mountains of the Caucasus and northern Iran, Iraq, and Turkey. It is also native to northern Morocco and has become naturalised in some other parts of the world.[9] In the southern parts of its range, it is mainly found in mountainous regions. Its light seeds are easily blown by the wind and it is a pioneer species, one of the first trees to sprout on bare land or after a forest fire. It needs plenty of light and does best on dry, acid soils and is found on heathland, mountainsides, and clinging to crags.[5] Its tolerance to pollution make it suitable for planting in industrial areas and exposed sites.[10] It has been introduced into North America, where it is known as the European white birch, and is considered invasive in the states of Kentucky, Maryland, Washington, and Wisconsin.[11] It is naturalised and locally invasive in parts of Canada.[12]
Betula pendula subsp. pendula – Europe and eastwards to central Asia
Betula pendula subsp. mandshurica(Regel) Ashburner & McAll. – eastern Asia and western North America; treated by some botanists as Betula platyphylla[14]
Betula pendula subsp. szechuanica(C.K.Schneid.) Ashburner & McAll. – western China, from Qinghai and Gansu to Yunnan and southeast Xizang, treated by some botanists as Betula szechuanica[14]
B. pendula is distinguished from the related B. pubescens, the other common European birch, in having hairless, warty shoots (hairy and without warts in downy birch), more triangular leaves with double serration on the margins (more ovoid and with single serrations in downy birch), and whiter bark often with scattered black fissures (greyer, less fissured, in downy birch). It is also distinguished cytologically, silver birch being diploid (with two sets of chromosomes), whereas downy birch is tetraploid (four sets of chromosomes). Hybrids between the two are known, but are very rare, and being triploid, are sterile.[15] The two have differences in habitat requirements, with silver birch found mainly on dry, sandy soils, and downy birch more common on wet, poorly drained sites such as clay soils and peat bogs. Silver birch also demands slightly more summer warmth than does downy birch, which is significant in the cooler parts of Europe. Many North American texts treat the two species as conspecific (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.[8]
Several varieties of B. pendula are no longer accepted, including B. pendula var. carelica, fontqueri, laciniata, lapponica, meridionalis, microlepis, and parvibracteata, as well as formsBetula pendula f. bircalensis, crispa, and palmeri.[13] Other synonyms include:[13][16]
The rejected name Betula albaL. also applied in part to B. pendula, though also to B. pubescens[17]
Betula brachylepisV.N.Vassil.
Betula cajanderi f. fruticansKozhevn.
Betula carpatica var. sudeticaRchb.
Betula coriaceaPamp.
Betula cycoviensisSteud.
Betula ellipticifoliaV.N.Vassil.
Betula etnensisRaf., sometimes spelled B. aetnensis[18]
Betula ferganensisV.N.Vassil.
Betula fontqueriRothm.
Betula gummiferaBertol.
Betula hybridaBlom
Betula insularisV.N.Vassil.
Betula kossogolicaV.N.Vassil.
Betula laciniata(Wahlenb.) Rchb.
Betula lobulataKit.
Betula ludmilaeV.N.Vassil.
Betula microlepisI.V.Vassil.
Betula mongolicaV.N.Vassil.
Betula montanaV.N.Vassil.
Betula oycowiensisBesser, sometimes spelled B. oycoviensis[1]
The silver birch has an open canopy which allows plenty of light to reach the ground. This allows a variety of mosses, grasses, and flowering plants to grow beneath, which in turn attract insects. Flowering plants often found in birch woods include primrose (Primula vulgaris), violet (Viola riviniana), bluebell (Hyacinthoides non-scripta), wood anemone (Anemone nemorosa), and wood sorrel (Oxalis acetosella). Small shrubs that grow on the forest floor include blaeberry (Vaccinium myrtillus) and cowberry (Vaccinium vitis-idaea).[8] Birds found in birch woodland include the chaffinch, tree pipit, willow warbler, nightingale, robin, woodcock, redpoll, and green woodpecker.[10]
The branches of the silver birch often have tangled masses of twigs known as witch's brooms growing among them, caused by the fungus Taphrina betulina. Old trees are often killed by the decay fungus Fomitopsis betulina and fallen branches rot rapidly on the forest floor. This tree commonly grows with the mycorrhizal fungus Amanita muscaria in a mutualistic relationship. This applies particularly to acidic or nutrient-poor soils. Other mycorrhizal associates include Leccinum scabrum and Cantharellus cibarius.[8] In addition to mycorrhiza, the presence of microfauna in the soil assists the growth of the tree, as it enhances the mobilization of nutrients.[19]
The larvae of a large number of species of butterflies, moths, and other insects feed on the leaves and other parts of the silver birch.[20] In Germany, almost 500 species of insects have been found on silver and downy birch including 106 beetles and 105 lepidopterans, with 133 insect species feeding almost exclusively on birch.[21]Birch dieback disease can affect planted trees, while naturally regenerated trees seem less susceptible.[22] This disease also affects B. pubescens and in 2000 was reported at many of the sites planted with birch in Scotland during the 1990s.[23] In the United States, the wood is attacked by the bronze birch borer (Agrilus anxius), an insect pest to which it has no natural resistance.[11]
Conservation
Betula pendula is considered a species of least concern by the IUCN Red List.[1] The synonym Betula oycowiensis (as B. oycoviensis) was previously listed on the Red List as vulnerable,[24] though it is now considered a synonym of B. pendula subsp. pendula.[1][13]B. szaferi was previously considered extinct in the wild on the Red List, but is now considered a form of B. pendula with the presence of a mutant gene, causing it to grow weakly and fruit heavily.[1]
Foliage coloring in autumnA pair of Finnish traditional shoes woven from strips of birch bark
The silver birch is Finland's national tree.[25] Leafy, fragrant bunches of young silver birch boughs (called vihta or vasta) are used to gently beat oneself while bathing in the Finnish sauna.[26] Silver birch is often planted in parks and gardens, grown for its white bark and gracefully drooping shoots, sometimes even in warmer-than-optimum places such as Los Angeles and Sydney. In Scandinavia and other regions of northern Europe, it is grown for forest products such as lumber and pulp, as well as for aesthetic purposes and ecosystem services. It is sometimes used as a pioneer and nurse tree elsewhere.[5]
Silver birch wood is pale in colour with a light reddish-brown heartwood and is used in making furniture, plywood, veneers, parquet blocks, skis, and kitchen utensils, and in turnery. It makes a good firewood, but is quickly consumed by the flames. Slabs of bark are used for making roof shingles and strips are used for handicrafts such as bast shoes and small containers.[5] Historically, the bark was used for tanning. Bark can be heated and the resin collected; the resin is an excellent waterproof glue and useful for starting fires. The thin sheets of bark that peel off young wood contain a waxy resin and are easy to ignite even when wet. The dead twigs are also useful as kindling for outdoor fires.[27] The removal of bark was at one time so widespread that Carl Linnaeus expressed his concern for the survival of the woodlands.[28]
Birch brushwood is used for racecourse jumps and besom brooms. In the spring, large quantities of sap rise up the trunk and this can be tapped. It contains around 1% sugars and can be used in a similar way to maple syrup, being drunk fresh, concentrated by evaporation, or fermented into a "wine".[27]
Phytochemicals
The outer part of the bark contains up to 20% betulin. The main components in the essential oil of the buds are α-copaene (~10%), germacrene D (~15%), and δ-cadinene (~13%).[29] Also present in the bark are other triterpene substances which have been used in laboratory research to identify its possible biological properties.[30]
Standardized allergen extract, white birch, sold under the brand name Itulatek, is indicated for the treatment of allergy to tree pollen from birch, alder and/or hazel and have allergic rhinitis (with or without conjunctivitis).[32][33]
Successful birch cultivation requires a climate cool enough for at least the occasional winter snowfall. As they are shallow-rooted, they may require water during dry periods. They grow best in full sun planted in deep, well-drained soil.[35]
Cultivars and varieties
'Carelica' or "curly birch" is called visakoivu in Finland. The wood is hard and burled throughout; it is prized for its decorative appearance and is used in wood-carving and as veneer.[36]
'Laciniata' agm[37] (commonly misidentified as 'Dalecarlica') has deeply incised leaves and weeping branches
Alders are trees comprising the genus Alnus in the birch family Betulaceae. The genus comprises about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few species extending into Central America, as well as the northern and southern Andes.
A birch is a thin-leaved deciduous hardwood tree of the genus Betula, in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus Betula contains 30 to 60 known taxa of which 11 are on the IUCN 2011 Red List of Threatened Species. They are a typically rather short-lived pioneer species widespread in the Northern Hemisphere, particularly in northern areas of temperate climates and in boreal climates.
Alnus glutinosa, the common alder, black alder, European alder, European black alder, or just alder, is a species of tree in the family Betulaceae, native to most of Europe, southwest Asia and northern Africa. It thrives in wet locations where its association with the bacterium Frankia alni enables it to grow in poor quality soils. It is a medium-sized, short-lived tree growing to a height of up to 30 metres (98 feet). It has short-stalked rounded leaves and separate male and female flowers in the form of catkins. The small, rounded fruits are cone-like and the seeds are dispersed by wind and water.
Betula pubescens, commonly known as downy birch and also as moor birch, white birch, European white birch or hairy birch, is a species of deciduous tree, native and abundant throughout northern Europe and northern Asia, growing farther north than any other broadleaf tree. It is closely related to, and often confused with, the silver birch, but grows in wetter places with heavier soils and poorer drainage; smaller trees can also be confused with the dwarf birch.
Betula nigra, the black birch, river birch or water birch, is a species of birch native to the Eastern United States from New Hampshire west to southern Minnesota, and south to northern Florida and west to Texas. It is one of the few heat-tolerant birches in a family of mostly cold-weather trees which do not thrive in USDA Zone 6 and up. B. nigra commonly occurs in floodplains and swamps.
Betula papyrifera is a short-lived species of birch native to northern North America. Paper birch is named for the tree's thin white bark, which often peels in paper-like layers from the trunk. Paper birch is often one of the first species to colonize a burned area within the northern latitudes, and is an important species for moose browsing. Primary commercial uses for paper birch wood are as boltwood and sawlogs, while secondary products include firewood and pulpwood. It is the provincial tree of Saskatchewan and the state tree of New Hampshire.
Betula alleghaniensis, the yellow birch, golden birch, or swamp birch, is a large tree and an important lumber species of birch native to northeastern North America. Its vernacular names refer to the golden color of the tree's bark. In the past its scientific name was Betula lutea.
Betula lenta is a species of birch native to eastern North America, from southern Maine west to southernmost Ontario, and south in the Appalachian Mountains to northern Georgia.
Betula nana, the dwarf birch, is a species of birch in the family Betulaceae, found mainly in the tundra of the Arctic region.
Betula glandulosa, the American dwarf birch, also known as resin birch or shrub birch, is a species of birch native to North America.
Betula populifolia is a deciduous tree native to eastern North America.
Betula uber, the Virginia round-leaf birch, is a rare species of tree in the birch family. One of the most endangered species of North American trees, it is endemic to Smyth County, in the U.S. state of Virginia. It is part of the temperate broadleaf and mixed forests biome.
Betula cordifolia, the mountain paper birch is a birch species native to Eastern Canada and the Northeastern United States. Until recently it was considered a variety of Betula papyrifera, with which it shares many characteristics, and it was classified as B. papyrifera var. cordifolia (Regel) Fern.
Betula utilis, the Himalayan birch, is a deciduous tree native to the Western Himalayas, growing at elevations up to 4,500 m (14,800 ft). The Latin specific epithet utilis means "useful", and refers to the many uses of the different parts of the tree. The white, paper-like bark was used in ancient times for writing Sanskrit scriptures and texts. It is still used as paper for the writing of sacred mantras, with the bark placed in an amulet and worn for protection. Selected varieties are used for landscaping throughout the world, even while some areas of its native habitat are being lost due to overuse of the tree for firewood.
Euceraphis punctipennis, the downy birch aphid or European birch aphid, is a species of aphid in the order Hemiptera. These aphids are tiny green insects with soft bodies and membranous wings. They are found living on downy birch trees where they feed and multiply on the buds and leaves by sucking sap.
Birch dieback is a disease of birch trees that causes the branches in the crown to die off. The disease may eventually kill the tree. In an event in the Eastern United States and Canada in the 1930s and 1940s, no causal agent was found, but the wood-boring beetle, the bronze birch borer, was implicated in the severe damage and death of the tree that often followed. In similar crown dieback occurrences in Europe several decades later, the pathogenic fungus Melanconium betulinum were found in association with affected trees, as well as Anisogramma virgultorum and Marssonina betulae.
Taphrina betulina is a fungal plant pathogen that causes the gall, witches broom, which is a chemical infection of birch buds or the developing shoots, leading to a proliferation of growth. It was first described by Emil Rostrup in 1883 and is found in Europe, New Zealand and North America.
Massalongia rubra is a species of gall midge which forms galls in the leaves of birch. It was first described by the French naturalist and entomologist, Jean-Jacques Kieffer in 1890 and is found in Europe.
1 2 Vakkari P (2009). "Silver birch (Betula pendula)"(PDF). EUFORGEN Technical Guidelines for Genetic Conservation and Use. Archived from the original(PDF) on 18 January 2017. Retrieved 17 January 2017.
↑ "Filsuvez EPAR". European Medicines Agency (EMA). 13 April 2022. Archived from the original on 6 July 2022. Retrieved 6 July 2022. Text was copied from this source which is copyright European Medicines Agency. Reproduction is authorized provided the source is acknowledged.
↑ Botanica's Trees & Shrubs. San Diego, Calif.: Laurel Glen Publishing. 1999. p.139. ISBN978-1-57145-649-6.
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