Plants 7-200+ cm. Stems usually sparsely to ± densely hirsute, often glabrescent, sometimes glabrate proximally, sometimes entirely so (hirsute in lines in arrays). Leaves: abaxial faces paler than adaxial, with a dark, distinct reticulum, adaxial without impressed main veins; array leaves usually equal to mid cauline. 2n = 16, 32. Flowering Aug-Oct. Wet soils, often peaty, open to moderately shaded, margins of alluvial deciduous woods and alder thickets, swamp margins, edges of bogs, stream and lake shores, marshes, wet meadows, early-melting coastal or riparian snowbeds with boreal forbs (northern alpine and subarctic regions), roadside and drainage ditches; 0-2000 m; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld. and Labr., N.S., Ont., P.E.I., Que., Sask.; Ala., Conn., Del., Ga., Ill., Ind., Iowa, Maine, Md., Mich., Minn., Mo., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Pa., R.I., S.C., S.Dak., Tenn., Vt., Va., W.Va., Wis.; introduced in Europe. The following forms that pertain to var. puniceum are not recognized here: Aster puniceus forma blandus (Pursh) Lepage, forma candidus Fernald, forma colbyi Shinners, forma demissus (Lindley) Fernald, forma etiamalbus Venard, and forma rufescens Fassett. Variety calderi is a dwarf morphotype at the northern limit of the range that does not deserve taxonomic recognition. Hybrids of var. puniceum with the following species have been reported: Symphyotrichum lanceolatum (probably A. tardiflorus Linnaeus var. lancifolius Fernald), S. lateriflorum, S. urophyllum, and S. cordifolium.