Glabrous annual or biennial 4-15 dm, commonly simple to near the top, leafy throughout, the lvs sessile, clasping, oblong to ovate or elliptic- obovate, rounded or obtuse at the tip, mostly 3-8 נ1-4 cm, spinose-dentate; heads few, large, the disk 1.5-3 cm wide; invol bracts slightly or moderately imbricate, the outer ones (at least) with long, loose or spreading green tip, at least the larger bracts generally well over 1 mm wide; rays ca 25-50, 1-2 cm; achenes glabrous, the central ones sterile; pappus rather scanty, eventually deciduous; 2n=12. Open or waste places; w. Mo. to La., Tex., and N.M., and intr. e. to Ill. Aug., Sept. (Prionopsis c.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.