Plants usually 200-300 cm. Leaves mostly alternate; blades narrowly to broadly lanceolate, apices acute to acuminate, abaxial faces hispid to hispidulous. Phyllaries: abaxial faces ± glabrate or sparsely hairy (longer hairs 0.5-1 mm). Flowering late summer-fall. Moist open places, ditches, roadsides; (300-)1200-2700 m; Alta., B.C., Man., Sask.; Ariz., Calif., Colo., Idaho, Kans., Mo., Mont., Nebr., Nev., N.Mex., N.Dak., Okla., Oreg., S.Dak., Utah, Wash., Wyo. Plants in the Dakotas and south-central and eastern Canada are intermediate between subsp. nuttallii and subsp. rydbergii and were placed by R. W. Long (1966) in subsp. canadensis; C. B. Heiser et al. (1969) returned this to subsp. nuttallii with the comment that it was hardly equivalent to other subspecies that they included in their treatment. The name H. ×luxurians may refer to hybrids between subsp. nuttallii and H. giganteus (Heiser et al.).