Stems 4-10(-15) dm, generally purple-speckled, viscid-puberulent at least near the top, scarcely or not at all glaucous; lvs mostly in 3's or 4's, thick and firm, often somewhat rugose, ovate or lance-ovate, relatively abruptly contracted to the short petiole, 5-12(-15) × 2-7 cm, coarsely serrate, ±strongly triplinerved; infl dense, slightly
to strongly convex, not large; invol 6.5-9 mm, often purplish, its bracts well imbricate, obtuse, often 3-5-nerved; fls purple, (4-)5-8(-10) per head; 2n=20. Moist places, especially in sandy or gravelly, acid soil; near the coast from N.S. and s. N.H. to S.C. July-Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.