Description from Flora of China
Shrubs or subshrubs, rarely perennial or annual herbs. Leaves opposite or upper ones alternate, stipulate or estipulate. Flowers solitary or inflorescences cymose, racemose, corymbose, or headlike, sometimes paniculate, few- to many-flowered. Sepals 5; outer 2 ca. 1/2 size of inner 3; inner 3 subequal, 3-6-veined, accrescent in fruit. Petals 5, yellow, orange-yellow, or pink. Styles filiform; stigmas large, capitate. Capsule 3-angled, 3-valved, 1-loculed or imperfectly 3-loculed. Seeds many.
About 110 species: N Africa, SW Asia, and Europe, mostly in the Mediterranean region, extending to C Asia, also in North and South America; one species in China.