Annual or perennial herbs, often succulent. Leaves alternate with a basal sheath enclosing the stem, often ciliate at the mouth. Inflorescences composed of cymes which may be few or numerous and aggregated into thyrses; sometimes subtended by or enclosed in spathes. Flowers actinomorphic or zygomorphic, bisexual or male, occasionally cleistogamous. Sepals 3. Petals 3, free or united, deliquescent, conspicuous, usually brightly coloured, often blue or yellow. Stamens 6, in 2 whorls; in some genera 1-4 modified into staminodes or suppressed. Style unbranched. Ovary superior, 2-3-locular. Fruit a 2-3-valved capsule, rarely indehiscent.