Science Fair Project Encyclopedia
White Birch (Betula pubescens) is an abundant tree throughout northern Europe, northern Asia and also Greenland. It is also sometimes known as European White Birch, Downy birch or Hairy birch. It is not a large tree, rarely exceeding 15-20 m tall and often less.
It is distinguished from the closely related Silver Birch (B. pendula) in having smooth, downy shoots (hairless and warty in Silver Birch), and less bright white, often dull greyish bark but rarely with any black fissures (whiter, often with conspicuous black fissures, in Silver Birch). It is also distinguished cytologically, Silver Birch being diploid (with two sets of chromosomes), whereas White Birch is tetraploid (four sets of chromosomes). The two have differences in habitat requirements, with White Birch commoner on wet, poorly drained sites such as clay soils and peat bogs, and Silver Birch found mainly on dry, sandy soils. Many North American texts treat the two species as conspecific (and cause confusion by combining the vernacular name 'White Birch' of one with the scientific name B. pendula of the other), but they are regarded as distinct species throughout Europe.
It extends further north into the Arctic than any other broadleaf tree. These subarctic populations are usually small and very contorted, and are often distinguished as Arctic White Birch, Betula pubescens subsp. tortuosa. This subspecies is notable as being the only tree native to Greenland, where large specimens can reach 5-6 m tall.
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