Leaves: abaxial faces glabrous or glabrate. 2n = 32. Flowering Jul-Aug. Alluvial stream shores; 10-200 m; Ont., Que.; Mich. Variety glabratum reaches farther north in Ontario and Quebec than does var. ontarionis, as far as the Clay Belt and streams of the James Bay basin. It may be present in Minnesota and Wisconsin. It may be confused with Symphyotrichum tradescantii, which is mostly allopatric. It is distinguished from the latter by its more deeply lobed disc corollas.