2b. var. laeve Torr. & A. Gray

S. speciosum Nutt.

Stems glabrous, strongly glaucous, appearing silvery or bluish green. Leaf blades with the upper surface glabrous, the undersurface glabrous or sparsely to moderately hairy only along the midvein, both surfaces moderately to strongly glaucous. Involucral bracts with both surfaces glabrous, the margins with minute, loosely ascending hairs. 2n=14. July–September.

Scattered in counties along the western margin of the state and uncommon sporadically farther east (Wyoming to New Mexico east to Wisconsin and Arkansas). Loess hill prairies, openings of mesic to dry upland forests, and tops of bluffs; also railroads.

This taxon has been regarded as a separate species by some botanists (Settle and Fisher, 1970). As noted by Steyermark (1963), it is striking and distinctive, but at least a few intermediates with var. integrifolium exist in Missouri for every character said to distinguish the two taxa.