Dioecious. Plants 3-20 cm (caudices branching or rhizomes stout). Stolons none. Basal leaves 3-nerved, narrowly oblanceolate, 10-60(-100) × 3-12 mm, tips acute, faces gray-woolly or tomentose. Cauline leaves linear, 5-40 mm, mid and distal flagged. Heads 3-9 in corymbiform arrays. Involucres: staminate 4.5-6 mm; pistillate 5-8 mm. Phyllaries (proximally light brown, dark brown, or olivaceous) distally whitish or light brown. Corollas: staminate 3-4.5 mm; pistillate 2.5-4 mm. Cypselae 1-1.6 mm, glabrous; pappi: staminate 4-5 mm; pistillate 3.5-5 mm. 2n = 28 (under A. neodioica). Flowering summer. Protected alpine and subalpine sites, gravelly or sandy soils near conifers at timberline; 1400-3400 m; Alta., B.C.; Calif., Idaho, Mont., Oreg., Utah, Wash., Wyo.