Plants cespitose; with cormoid caudices, not strongly rhizomatous. Stems 1-10+, decumbent to ascending or erect to arching. Involucres broadly campanulate (fresh). 2n = 10. Flowering Jul-Sep(rarely Oct). Prairies and lower elevations in mountains, hillsides, lake shores, salt flats, stream banks and bars, railroad rights-of-way, roadsides, disturbed soils, seasonally dry grounds; 200-2400 m; Alta., B.C., Man., N.W.T., Ont., Sask.; Ariz., Colo., Idaho, Kans., Minn., Mont., Nebr., N.Mex., N.Dak., Oreg., S.Dak., Utah, Wash., Wyo. Variety pansum is reported to be rare in extreme western Kansas and Ontario (where it is introduced), extreme northeastern Arizona, and northwestern New Mexico. It has been introduced along railroads farther east. A. G. Jones (1978) treated this taxon as a subspecies with two varieties. Plants forming clumps with many, erect to arching, stout, usually densely hispido-strigose stems were called var. pansum; these occur mostly in British Columbia, Idaho, Oregon, and Washington. Plants in clusters with few, decumbent or ascending, slender, usually sparsely strigose stems were recognized by Jones as var. stricticaule; these are encountered mostly on the prairies and in the foothills of the Rocky Mountains from Alberta to Manitoba, Utah, and Wyoming.