Perennial, 3-6 dm, the stem pithy; lower lvs once pinnate, the lfls varying from ovate or subrotund and merely serrate to pinnately deeply dissected; upper lvs much reduced, sometimes consisting only of the sheath; fls white; fr glabrous, ovoid, 2-2.5 mm, obscurely ribbed, each mericarp nearly semicircular in cross-section; 2n=40. Native of Eurasia, escaped or adventive in waste places; Nf. to DC., inland to Wis. and Ind. July-Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.