Freely branched, taprooted annual to 1 m, the stem retrorsely, the lvs antrorsely rough-strigose or partly glabrous; lvs ovate or lance-ovate in outline, 2-3 times pinnate, or the upper only once pinnate, at least the lower pinnae generally evidently petiolulate, the ultimate segments rather small; peduncles terminal and lf-opposed, 3-16 cm, invol wanting, or of a single slender bract; rays 2-10, 0.5-2.5 cm; pedicels 1-4 mm; fr ovoid-oblong, 3-5 mm, covered with widely spreading, nearly straight, cylindric-subconic, slightly upcurved prickles approaching 1 mm; 2n=12. Native of Europe, now well established as a weed in s. U.S., n. to D.C., O., Ill., and Kans. June, July.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
