Coarse perennial 0.6-2 m, glabrate below, viscid-villous or stipitate-glandular above; lvs large, thin, to 3 dm, broadly oblong to ovate, pinnately few-lobed, also toothed, the petiole wingless or winged only near the blade; heads in congested cymes ending the branches, the pale yellow disk 6-13 mm wide; invol bracts lanceolate to lance-linear, narrower and often shorter than the bracts that subtend the ray-achenes; cor of pistillate fls minute and tubular, or expanded into a short, whitish ray to 10(-15) mm; achenes 3-4 mm, unequally 3-ribbed and -angled, not striate; 2n=30. Moist woods, especially in calcareous regions; Vt. and Ont. to Minn., s. to Ga. and Ark. June-Oct. (P. radiata, the radiate form)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.