Aromatic, subglabrous stout perennial 5-15 dm from a coarse, branching rhizome; lvs large, the lower broadly deltoid and ±biternate, the lfls oblong or obovate, sharply and irregularly serrate (often doubly so), and commonly each 2-3-lobed or -parted; umbels large, long-peduncled, to 15 cm wide; bracts none; bractlets setaceous, deciduous; sep none; pet white; fr suborbicular, 4-5 mm; oil-tubes solitary in the intervals, 2 on the commissure; 2n=22. Native of Europe, adventive here and there in the n. part of our range. June, July. (Imperatoria o.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.