Plants (20-)30-100(-120) cm. Leaves: proximal blades usually entire, rarely serrate; mid and distal leaves entire. Heads 20-100(-200+). Peduncles 2-5(-7) cm. Involucres 5-8 × 5-8 mm. Ray florets 10-14; corollas 5.5-11.5 × 2.7-5.2 mm. Disc florets 150-300(-500+). Cypselae 0.6-0.9 mm; pappi 0.05-0.2 mm. 2n = 26.

Flowering (May-)Jun-Aug (sometimes again in fall). Calcareous soils, ditches, washes, along streams; 100-600 m; Ark., Okla., Tex.