Annual, biennial or most commonly perennial herbs. Stems erect or prostrate. Leaves alternate, entire, toothed or divided, frequently rosulate at base. Heads heterogamous, radiate, solitary or few in loose racemes, sometimes more numerous. Involucre campanulate, bracts in 2 or 3 series, narrow, varying from herbaceous to scarious. Receptacles flat or convex, naked. Ray florets pistillate, fertile, numerous, in 1 or more marginal rows, ligules long, narrow, rarely very short, white, pink or purplish, rarely yellow. Disc florets bisexual, fertile, commonly several times as many as ray florets, corolla mostly yellow, 5-lobed, lobes sometimes purplish. Achenes commonly narrowly ellipsoid or obovoid, sometimes compressed. Pappus mostly double, outer row of scales or absent, inner row of fine, mostly fragile bristles; pappus very rarely absent.
A large and difficult cosmopolitan genus of more than 200 species, especially abundant in temperate regions of North America; in Taiwan, two species, one of which is represented by two varieties.