The birch family is represented in Alaska by the birch (Betula) and the alder (Alnus) genera and 10 species with intergrades and hybridizing between them. Leaves are single with teeth of 2 sizes in the alder.
Flower clusters are catkins apppearing in early spring before the leaves. They are minute greenish flowers from a bud that partially formed the summer before. Male flowers have pollen in narrow long catkins at twig ends. Short fermale flowers in catkins on sides of the twigs. Fruits are conelike.
Birch trees have papery peeling bark and generally have twigs dotted with glands. Alders have smooth bark and in all seasons usually have old dead, dark cone-like fruit on the twigs.