Deciduous, dioecious (or rarely monoecious) trees or shrubs. Leaves alternate, simple, usually with stipules. Flowers in catkins, each flower solitary in the axil of a bract (here called a scale or catkin-scale). Perianth absent or very small, but flowers of both sexes usually with a cup-like disc or 1 or 2 small nectaries at base. Stamens 2 to many; filaments long and slender, occasionally connate. Ovaries of 2 carpels, 1-celled, with 2 or 4 parietal placentae. Style 1 or rarely 2; stigmas 2, often bifid. Fruit a 2- to 4-valved capsule; seeds enveloped by long silky hairs arising from the funicle; endosperm absent; embryo straight.

Contains 3 genera, the third, Chosenia, with a single species in north-east Asia.

Populus L.

Deciduous, almost always dioecious trees with soft, light wood and monopodial branching. Buds with several imbricate outer scales, often viscid and balsam-scented; terminal bud usually present. Leaves alternate, usually broad, commonly ovate and more or less cordate at base; petiole long, often strongly compressed laterally; stipules generally inconspicuous and caducous. Inflorescence usually without foliaceous bracts; flowers opening before the leaves, in pendulous catkins, wind-pollinated; catkin-scales toothed or laciniate; each flower with a cup-like disc. Stamens of male catkins 4 to many, with short filaments; anthers red or purple. Ovaries of female catkins with 2–4 carpels; style 1; stigmas 2, sessile or subsessile, frequently dilated apically. Capsules 2- to 4-valved; valves sometimes suberect or indistinctly recurved at maturity.