Perennial herb with long rhizomes; stems erect, terete to slightly ribbed, with short, simple hairs in lines or stripes above, at least in infl., becoming glabrous below, branched only above, 50-150 cm tall. Mid cauline lvs narrow-lanceolate, apetiolate and cuneate, acute to acuminate, entire or serrulate to remotely serrate, glabrous or sparsely hairy about margins 70-150-(200) × 6-12-(15) mm; uppermost lvs smaller. Infl. a many-headed, narrow panicle. Capitula c. 15-25 mm diam.; peduncles with lines or stripes of simple hairs. Involucral bracts somewhat unequal; inner bracts linear-lanceolate, acute to acuminate, glabrous, with a diamond-shaped green patch near apex and extending down midrib, also sometimes tinged or spotted purple, 5-6 mm long; outer bracts not wholly herbaceous, c. 3-4 mm long. Ray florets numerous; ligules usually white, sometimes flushed pink or violet, 8-12 mm long. Achenes subcylindric to obovoid, slightly compressed, 4-5-ribbed, 2-2.5 mm long, with sparse antrorse hairs.