Plants 30-200 cm; basal offshoots and stolons present or absent. Stems erect (slender). Leaf blades linear to narrowly lanceolate; cauline 25-115 × 3-17 mm, bases not decurrent. Heads 30-100+ in paniculiform arrays, primary branches mostly spreading; only proximal bracts leaflike, others reduced, linear to linear-oblanceolate or subulate, 8-55 × 1-6 mm. Peduncles 5-185 mm; bracts 3-10, linear to linear-oblanceolate or subulate, 2-10(-15) mm. Involucres 2.5-3 × 2.5-6 mm. Phyllaries in 4-6 series, subulate or linear-oblong, unequal, 6-8 merging down peduncles; outer 1-1.8 × 0.3-0.6 mm; inner 1.8-3 × 0.3-0.7 mm. Ray florets 20-40; corolla white to lilac, laminae 3-6.3 mm, tubes 0.6-1.35 mm. Disc florets 50-135; corollas 1.2-2.5 mm. Cypselae obovoid, 1.6-2.5 × 1-1.6 mm, wings 0.2-0.4 mm wide; pappus awns 0.3-0.7 mm.
Mostly 5-15 dm; lvs mostly linear or nearly so, the larger ones mostly 3-11 cm and to 0.5 or 1(-2) cm wide, but the lower lvs commonly deciduous, so that the lvs in well grown flowering plants are rarely more than 0.5(-1) cm wide; infl diffusely branched, merely subulate-bracteate, the bracts commonly less than 1 cm; invol bracts narrow, acute or acuminate, evidently imbricate; rays white or lilac, mostly 5-8 mm; disk mostly 3-6 mm wide; achenes evidently wing- margined; pappus-awns less than 1 mm, or sometimes obsolete; 2n=18, 36. Moist or wet to sometimes rather dry places; se. U.S., n. to N.C., Ky., s. Ill., and Mo., and w. to Okla. and e. Tex. July-Oct.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.