Plants openly colonial; rhizomes 1-3+ from base of each stem, herbaceous, ± woody with age. Stems 1, often glabrate proximally to ± villous, distally stipitate-glandular. Leaves: proximal scalelike, withering by flowering; blades (16-)50-130 × (4-)10-30(-40) mm, reduced distally, thin, bases auriculate-clasping, margins ± scabrous to (distal) stipitate-glandular. Heads (1-)2-40+. Peduncles sometimes villous, densely stipitate-glandular; bracts 1-2(-3), linear-lanceolate, stipitate-glandular. Phyllaries squarrose, innermost appressed, apices often ± purplish, acuminate. Ray floret laminae 7-11(-15) × 0.8-1.2 mm. Disc floret corollas 5-7 mm, glabrous, lobes 0.5-0.7 mm. Cypselae stramineous, stipitate; pappi surpassing or ± equaling disc corollas. 2n = 18.

Flowering late summer-early fall. Cold, wet soils, often ± calcareous, moist woodlands, often along streams, lake shores, alder thickets, open fields, cedar swamps, in montane and boreal forests; 0-1300+ m; Alta., B.C., Man., N.B., Ont., Sask., Yukon, Que.; Alaska, Idaho, Mich., Minn., Mont., N.Dak., Oreg., Wash.

Plants with long creeping rhizomes, the stems mostly arising singly, 3-10 dm, densely stipitate-glandular, at least upwards, and often ±spreading-hairy as well; lvs chiefly cauline, thin, lanceolate, remotely and rather saliently dentate to entire, 4.5-13 cm נ8-40 mm, sessile and obscurely to usually ±evidently auriculate-clasping, glabrous or scaberulous above, softly hairy to glabrous beneath; heads several or occasionally rather many in a short infl, the invol 7-11 mm, its thin, slender, bracts acuminate or attenuate, often deep purplish, about equal, loose, the outer herbaceous to the base; rays 20-40, dark purple, 1-1.5 cm; achenes evidently nerved, sparsely short-hairy; 2n=18. Moist, open or wooded places; Isle Royale, n. Minn., and w. Ont. to Alas. and Oreg. (A. major)

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

©The New York Botanical Garden. All rights reserved. Used by permission.