Semi-succulent, annual or perennial herbs, often climbing by coiling petioles; producing mustard oil. Leaves alternate, peltate or palmate, entire or lobed; stipules present (sometimes in seedlings only) or absent. Flowers solitary in axils, bisexual, showy, zygomorphic; sepals 5, free or shortly fused, the upper (adaxial) one (or sometimes 3) forming a backward-projecting nectariferous spur; petals 5, free, clawed, the 2 upper differing from the 3 lower, the latter sometimes reduced or absent; stamens 8, in 2 series of 4, all free, anthers basifixed, opening by lateral longitudinal slits; ovary superior, 3-locular, ovules 1 per locule, style terminal, trifid near apex. Fruit separating into 3, 1-seeded drupe-like or nut-like mericarps, or rarely a samara.
3 genera with c. 92 species, all occurring from Mexico to the southern parts of South America; 1 species naturalised in Australia.