Birch Family — Betulaceae
|Photo courtesy of Wikimedia Commons.|
While species in this family of shrubs and trees often grow to an impressive size in southern Canada, their Arctic counterparts are diminutive. The tallest species rarely exceed a metre in height!
General Information and Anatomy
Birches possess scaly buds and characteristic reproductive structures called catkins – these are dense spikes bearing many small flowers. Male catkins droop, while female catkins are more erect. The seeds contained within these structures are an important source of food for many arctic birds, especially ptarmigans. The dwarf birch, Betula glandulosa, grows on the low arctic tundra, in peat bogs or on acidic rocks, and is often associated with willows. Its branches are ordinarily dotted with wart-like glands and covered in a greyish waxy layer. The wood of this shrub was probably used by the Inuit for firewood, while children of Bathurst Inlet make use of the stickiness of newly unfolded birch leaves to make earrings.
In the extreme southern limits of the Arctic, the green alder, Alnus crispa, forms dense scrub in sheltered river valleys, along lake shores, and on treeless barrens by north-flowing rivers. Contrary to its name, the green alder actually has reddish- or greyish-brown bark. The large leaves are oval, somewhat crinkled, and have toothed margins. The green alder's method of reproduction is also unique to the family in that it does not require fertilization to produce seeds – a process known as apomixis.