Annual or perennial soft-wooded herbs or shrubs, more or less succulent, glabrous. Leaves usually alternate, often small and overlapping, usually sessile, borne in terminal clusters. Inflorescence a thyrse, usually with several dichasia each terminating in monochasial branches, rarely with only monochasia; peduncle sometimes scape-like. Sepals 4–5(–9), fleshy, free or basally fused, sometimes spurred; petals 4–5(–8), spreading, free or basally fused, yellow, white or pink; stamens usually twice as many as petals, in 1 or 2 whorls, shorter than petals; carpels usually free, each with many ovules. Seeds with longitudinal ridges, usually tuberculate.
About 600 species, widely distributed mostly in the Northern Hemisphere; 4 species naturalised in Australia.