Stout, to 2 m, glabrous or nearly so to the infl; lower lvs 1-3 dm, long-petiolate, the upper progressively reduced, with broad, sheathing petioles; lfls ovate to lanceolate, 4-10 cm, acute, sharply serrate, thinly margined and only rarely ciliate, glabrous or minutely hairy beneath; umbels 1-2 dm wide, with 20-45 thinly hairy rays; fr oblong-elliptic, 4-6.5 mm, rounded at base, glabrous, the lateral wings thin, flat, broad; oil-tubes numerous; seed loose in the pericarp; 2n=22. Swamps and wet woods; Lab. to Minn., s. to Del., W.Va., and Ind. June-Aug.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.