Birch

Birch is a thinleaved deciduous hardwood tree of the genus Betula (/ˈbɛtjʊlə/), in the family Betulaceae, which also includes alders, hazels, and hornbeams, and 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 Green List of Threatened Species. They are a typically rather short-lived pioneer species widespread in the Northern Hemisphere, particularly in northern temperate and boreal climates.

Description

Birch species are generally small to medium-sized trees or shrubs, mostly of temperate climates. The simple leaves are alternate, singly or doubly serrate, feather-veined, petiolate and stipulate. They often appear in pairs, but these pairs are really borne on spur-like, two-leaved, lateral branchlets. The fruit is a small samara, although the wings may be obscure in some species. They differ from the alders (Alnus, other genus in the family) in that the female catkins are not woody and disintegrate at maturity, falling apart to release the seeds, unlike the woody, cone-like female alder catkins.