Trees or shrubs, sometimes prostrate and rooting at nodes; bark rough and fissured or smooth. Winter buds with 1 outer scale. Lvs usually alternate, rarely opposite, entire or shallowly toothed; petiole usually short; stipules sometimes 0 or inconspicuous, sometimes conspicuous, usually caducous, especially on strong vegetative shoots; lamina generally lanceolate or elliptic to obovate, often with glandular margin. Small lvs often present at base of lateral shoots. Catkins erect or pendulous, appearing before, with, or after lvs. Fls entomophilous, each subtended by an entire bract. Perianth reduced to 1-2-(4) glands, more rarely these united to form a basal semi-annular lobed ring. ♂ fls with (1)-2-(12) stamens; anthers usually yellow, sometimes red. ♀ fls with 1 short or very short style and 2 stigmas. Capsule 2-valved, usually maturing well after lf maturity. Seeds nearly always numerous, very small or minute.