Annual fibrous-rooted herbs, or perennials with a rhizome or erect, woody subterranean rootstock. Leaves rosetted at base. Flowering stems erect, leafless, but with a pair of opposite, connate leaves or leaf-like bracts subtending the inflorescence; axillary hairs absent. Inflorescence cymose, sometimes appearing umbellate; bracts present or absent; sepals free or shortly united at base, persistent in fruit; petals 5, free or shortly united at base; stamens 5; ovary superior, ovules 3 or 6; style cleft into 3 stigmatic arms. Capsule splitting longitudinally into 3 valves; seeds 3 or 6.
About 25 species, most native to North America; 1 species naturalised in Australia.