Betula pendula

Taxobox
name = Silver Birch

---

image_width = 240px
image_caption = "Betula pendula"
regnum = Plantae
divisio = Magnoliophyta
classis = Magnoliopsida
ordo = Fagales
familia = Betulaceae
genus = "Betula"
subgenus = "Betula"
species = "B. pendula"
binomial = "Betula pendula"
binomial_authority = Roth
synonyms=
*"B. verrucosa" Ehrh.

"Betula pendula", (Variously Silver Birch, European Weeping Birch, European White Birch, or Weeping Birch) is a widespread European birch, though in southern Europe it is only found at higher altitudes. Its range extends into southwest Asia in the mountains of northern Turkey and the Caucasus. It is also found growing wild throughout much of Canada. The closely related "Betula platyphylla" in northern Asia and Sichuan Birch ("B. szechuanica") of central Asia are also treated as varieties of Silver Birch by some botanists, as "B. pendula" var. "platyphylla" and "B. pendula" var. "szechuanica" respectively (see birch classification).

Description

"Betula pendula" is a medium deciduous tree, typically reaching 15-25 m tall, exceptionally up to 39 m [ Väre H., Kiuru H., "Suomen puut ja pensaat" ("Trees and shrubs of Finland"), Metsäkustannus Oy, 2006 ] , with a slender crown of arched branches with drooping branchlets. The bark is white, often with black diamond-shaped marks or larger patches at the base. The shoots are rough with small warts, and hairless, and the leaves 3-6 cm long, triangular with a broad base and pointed tip, and coarsely serrated margins. The flowers are wind-pollinated catkins, produced before the leaves in early spring, the small (1-2 mm) winged seeds ripening in late summer on 3-5 cm long catkins.

It is distinguished from the related Downy Birch ("B. pubescens", the other common European birch) in having hairless, warty shoots (hairy, without warts 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). The two have subtle 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.

B. pendula commonly grows with its symbiotic fungus Amanita muscaria in a mutualistic relationship. This applies particularly to acidic or nutrient poor soils.

Cultivation and uses

It is often planted as a garden and ornamental tree, grown for its white bark and gracefully drooping shoots even in warmer-than-optimum places such as Los Angeles and Sydney. In Scandinavia and other regions of northern Europe, it is grown for forestry. It is sometimes used as a pioneer and nurse tree elsewhere.

Successful birch cultivation requires a climate cool enough for at least the occasional winter snowfall. Shallow rooted they require water during dry periods, growing best in full sun or dappled shade. They require deep, moist, fertile soil. [Botanicas' Trees & Shrubs, Random House, Sydney, 2005]

Cultivars

* Purpurea has rich dark purple leaves.
* Laciniata (commonly misidentified as Darlecarlica) has deeply incised leaves and weeping branches.
* Tristis has and erect trunk with weeping branchlets.
* Youngii has growth similar to a weeping willow (Salix sp.) with no central leader requiring grafting onto a standard.
* Carelica is called "curly birch" in Finland; "curly" refers to grain of wood [http://www.visaseura.com/18]

Cultural significance

Silver Birch is Finland's national tree. Occasionally one uses leafy, fragrant boughs of Silver Birch to gently beat oneself in a sauna. The boughs are called vihta or vasta. This has a relaxing effect on the muscles.

Land of the Silver Birch is a traditional Canadian folk song, though the birch referred to is actually a different species, Paper Birch "Betula papyrifera".

ee also

*List of Lepidoptera that feed on birches

References