Lower lvs twice ternate, the upper once ternate or irregularly compound; lfls ovate to lanceolate, finely serrate, the ascending teeth averaging 5-10 per cm of margin; rays 10-18, the outer ones of the terminal umbel becoming 3-5 cm and stiffly ascending; fr oblong-ovoid, 3-4 mm, half as wide; 2n=22. Moist fields and meadows; Que. and Me. to Sask., s. to Fla. and Tex. May, June.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Rather frequent in moist soil in most parts of the state. Moist woodland and very often in moist places along roadsides. Usually in small colonies. Gray, Man., ed. 5 and Wood, Classbook of 1865 did not make the distinction between this species and Thaspium trifoliatum var. flavum very clear and both were known to authors as Thaspium aureum Nutt. Consequently both species were reported under the last name by authors before our present manuals were in use so that it is impossible to know which species the author had in hand.