Betula glandulosa to tall, often forming dense thickets. The trunks are slender, rarely over diameter, with smooth, dark brown bark. The leaves are nearly circular to oval, long and broad, with a toothed margin. The fruiting catkins are erect, long and broad. It is closely related to the dwarf birch ("Betula nana"), and is sometimes treated as a subspecies of it, as "B. nana" subsp. "glandulosa". It is distinguished from typical "B. nana" by the presence of glandular warts on the shoots and longer leaf petioles. Hybrids with several other birches occur. Betula glandulosa Betula glandulosa, the American dwarf birch, also known
Alnus cordata with a very long season in leaf, from April to December in the Northern Hemisphere; they are alternate, cordate (heart-shaped), rich glossy green, 5–12 cm long, with a finely serrated margin. The slender cylindrical male catkins are pendulous, reddish and up to 10 cm long; pollination is in early spring, before the leaves emerge. The female catkins are ovoid, when mature in autumn 2–3 cm long and 1.5–2 cm broad, dark green to brown, hard, woody, and superficially similar to some conifer cones. The small winged seeds disperse through the winter, leaving the old woody, blackish 'cones' on the tree