Monographs Details: Silphium perfoliatum var. laeve Torr. & A.Gray
Authority: Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Description:Variety Description - The less hairy phase; peduncles, invol bracts, stem, and lower surfaces of the lvs glabrous or nearly so, often somewhat glaucous; typically in the mixed-grass prairie, to the w. of var. integrifolium, and barely entering our range; an outlier in c. Tenn. (S. speciosum)