Colonial from well developed creeping rhizomes; stems 2-10 dm, often zigzag, pubescent in lines, becoming uniformly so under the heads and glabrate toward the base; lvs chiefly cauline, scabrous to glabrous above, glabrous or loosely hairy along the midrib beneath, the main ones mostly 6-20 נ1-5 cm, with ovate or lanceolate, serrate, acuminate blade abruptly contracted into a relatively long, generally entire, broadly winged, strongly auriculate-clasping petiolar base; heads several or many in an open, sparsely leafy-bracteate infl; invol glabrous, 5-7 mm, its bracts acute or obtusish, seldom much imbricate, rather loose, often with spreading tip, the outer sometimes wholly herbaceous; rays 20-35, blue or pale purple (white), 7-15 mm; achenes strigose; pappus yellowish; 2n=32, 48, 64. Streambanks, meadows, and moist woods; N. Y. to Minn., s. to D.C., Ky., Io., and in the mts. to N.C. and Tenn. (A. oticus)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.