Perennials, 10-160 cm (usually cespitose, induments usually of stipitate-glandular and smooth-surfaced, curved or twisted woolly hairs, plants with caudices or short rhizomes, roots fibrous). Stems ascending or erect, simple, glabrate, puberulent, pilose, cottony, or woolly, eglandular or glandular. Leaves cauline; alternate; sessile (proximal withering by flowering; proximalmost reduced, scalelike) ; blades (1-nerved) ovate, elliptic, oblong, lanceolate, or linear (± uniform in size), margins entire, faces glabrate, scabrous, cottony, or woolly, eglandular or stipitate-glandular. Heads radiate or discoid, usually in open, racemiform, paniculiform, or corymbiform arrays, sometimes borne singly. Involucres turbinate-cylindric, turbinate, turbinate-obconic, or campanulate, 10-25 mm diam. Phyllaries 20-50 in 3-6 series, ± unequal (± appressed, often reddish or purplish at margins and tips), 1-nerved (keeled), ovate, lance-oblong, lanceolate, linear-oblong, or linear, chartaceous at bases, margins sometimes hyaline, especially proximally; apices acute to obtuse, green, usually puberulent, tomentose, and/or stipitate-glandular, sometimes glabrous. Receptacles ± flat, pitted, epaleate. Ray florets 0-21 (usually 5, 8, or 13), pistillate, fertile; corollas violet-purple, purple, pink, or white . Disc florets 10-35, bisexual, fertile; corollas yellow, ± ampliate, tubes shorter than funnelform throats, lobes 5, erect or reflexed, triangular; style-branch appendages lanceolate. Cypselae ± obconic, flattened, laterally 1-2-ribbed, sometimes with 1-2 additional nerves on each face, glabrous, pilose, or strigose, eglandular; pappi persistent, of 30-50 whitish to tawny, barbellate or smooth, apically clavate or more conspicuously barbellate bristles in 2(-3) series (outer usually 1 mm or less, sometimes 0, inner 5-10 mm). x = 9. Eucephalus, a relatively well-marked western North American group, has been treated as a section of Aster or as a distinct genus. Recent molecular evidence places Eucephalus, together with the eastern North American Doellingeria, at the base of the North American clade of Astereae.