Herbs annual, biennial, or perennial, usually glabrous. Stems erect to decumbent. Leaves opposite or alternate, rarely verticillate, short petiolate to sessile, margin entire. Flowers solitary, axillary, 5-merous. Calyx parted nearly to base; lobes spreading. Corolla blue, red, or white, rotate or infundibuliform; tube very short or obsolete; lobes contorted in bud. Stamens attached at base of corolla; filaments usually pubescent; anthers ellipsoid, apex obtuse, dorsifixed. Ovary ovoid; style filiform; stigma obtuse. Capsule globose, circumscissile, many seeded.

Approximately 28 species distributed throughout the temperate zone in Africa, Asia, Europe, North America, and South America; one species occurs in China.