Involucres usually 2-3 mm. 2n = 18, 36.

Flowering Aug-Oct. Dry to moist soils, disturbed soils, prairies, grasslands, near streams and ponds, roadsides, edges of thickets; 0-1600 m; Alta., B.C. , Man. , Ont. , Sask.; Colo., Ill., Iowa, Kans., Minn., Mo., Mont., Nebr., N.Mex., N.Dak., Okla., S.Dak., Tex., Wyo.; Mexico (Chihuahua).

Subspecies gilvocanescens replaces subsp. altissima on the Great Plains. Tetraploids of the two subspecies are difficult to distinguish.