Leaves: abaxial faces moderately to densely hairy. 2n = 32.

Flowering Aug–Oct. Often shaded, usually moist, alluvial soils, alluvial stream or lake shores, floodplain deciduous forests or thickets, bogs, marshes, edges of fields, roadsides; 10–300+ m; Ont., Que.; Ala. , Ill., Ind., Iowa, Kans., Ky., La., Mich., Minn., Miss., Mo., Nebr., N.Y., N.C., Okla., Pa., S.Dak., Tenn., Tex., Vt., Wis.

A. G. Jones (1989) suggested that var. ontarionis hybridizes with Symphyotrichum lanceolatum, S. lateriflorum, and S. racemosum. Existence of such hybrids needs confirmation.