Fibrous-rooted annual weed 0.1-2.5 m, glabrous or sometimes ±spreading-hairy throughout; lvs to 20 נ8 cm, sharply serrate with callous-tipped teeth, sometimes also irregularly lobed, the lower oblanceolate to obovate, tapering to a short petiolar base, the middle and upper more elliptic, lanceolate, or oblong, and, especially in robust specimens, often auriculate-clasping; heads in a flat-topped or elongate infl, or solitary in depauperate plants, turbinate-cylindric; invol 1-1.5 cm; pappus copious, bright white, eventually deciduous; 2n=40. Various habitats, including dry woods, marshes, and waste places; Nf. to Fla., w. to Nebr. and Tex., and intr. elsewhere. Aug., Sept. Most of our plants are var. hieraciifolia, with the denuded receptacle of old heads 5-8 mm wide, and the achenes 2-3 mm, with mostly 10-12 ribs. The var. megalocarpa (Fernald) Cronquist, a well marked ecotype of saline coastal marshes from Mass. to N.J., is somewhat fleshy, with slightly larger heads that are more conspicuously swollen at base (the denuded receptacle 9-12 mm wide), and with larger achenes, these 4-5 mm, 16-20-ribbed.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.