Stems often with swollen nodes. Leaves opposite, simple, entire, stipulate or estipulate. Inflorescence variously cymose or solitary.
Flowers perfect, regular.
Sepals 5 or 4, distinct or connate. Stamens 10, distinct, free or in some apetalous genera adnate to the sepals. Hypanthium present in a few genera. Fruit a capsule or achene. The family includes many colorful ornamentals, wildflowers and numerous weedy species.