Dioecious, deciduous trees or shrubs with simple alternate lvs. mostly with stipules. Wood soft, light, mostly pale. Winter buds scaly. Roots often producing new shoots. Flowers early in spring, often before the leaves, in unisexual aments, the entire catkin falling away at once. Perianth none; each flower subtended by a scalelike bract. Stamens 2-many, sometimes 1 by fusion. Ovary 1-celled, ovoid to globose; stigmas 2-4. Fruit a 2-4-valved caps., with many minute comose seeds. (Munz, Flora So. Calif. 771).
Three or more genera, of over 300 species mostly in temperate climates, most abundant in the northern hemisphere. (Bailey 318).