Plants 40–120 cm. Stems sparsely (proximally) to densely hirsute distally. Leaves firm, basal and proximal long-petiolate, petioles ± winged; proximal cauline blade bases ± cordate or truncate, sometimes obliquely. Heads in ample, paniculiform arrays with divaricate or ascending, bracteate, often racemiform branches. Peduncles ± secund, 0–4 cm, bracteate. Involucres campanulate, (3.5–)4.5–7 mm. Ray corollas usually bright blue, light purple, bluish violet, or lavender, sometimes white. Cypselae glabrous. 2n = 16, 32.

Flowering Aug–Oct. Mostly shaded, loamy or rocky, mesic to dry soils, open deciduous woods, clearings, thickets, stream banks and edges of swamps, sometimes roadsides or ditches; 10–500+ m; Ala., Ark., Ga., Ill., Ind., Iowa, Kans., Ky., La., Md., Mich., Minn., Miss., Mo., Nebr., Ohio, Okla., Pa., Tenn., Tex., W.Va., Wis.

Variety drummondii is often confused with Symphyotrichum urophyllum, a usually white-rayed species with erect array branches. Hybridization has been reported with S. urophyllum, as well as with S. shortii or S. undulatum (the name Aster ×finkii Rydberg possibly applies to such hybrids).