Downy Birch

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Downy Birch (Betula pubescens) is an abundant tree throughout northern Europe, northern Asia and also Greenland. In Britain this species is most commonly referred to simply as Birch to distinguish it from Silver Birch (B. pendula). The term Downy Birch, a translation of the latin name, is often used when clarification is required. Many North American texts confuse the two species and often use the term White Birch to refer to either or both. It is also sometimes known as European White Birch or Hairy Birch.

It is not a large tree, rarely exceeding 15-20 m tall and often less. Downy Birch can be distinguished from the closely related Silver Birch (B. pendula) in having smooth, downy shoots, which are hairless and warty in Silver Birch. The bark of the Downy Birch is a dull greyish brown whereas the Silver Birch has striking white papery bark with black fissures. 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 differences in habitat requirements, with Silver Birch more common on wet, poorly drained sites such as clays and peat bogs, and Downy Birch found mainly on dry, sandy soils.

It extends farther north into the Arctic than any other broadleaf tree. These subarctic populations are usually small and very contorted, and are often distinguished as Arctic Downy 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.

See also Birch and Betula classification.

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