Aerial shoots 5-30(-35) cm, from short caudices on rhizomes, rhizomes primarily horizontal. Basal leaves 1-5(-7), ternate; petiole 1-10 cm; terminal leaflet sessile, obtriangular, (0.5-)0.7-1.8(-2.2) × 0.5-1.3 cm, base cuneate, margins crenate to broadly serrate on distal 1/3, apex obtuse to truncate, surfaces villous to nearly glabrous; lateral leaflets usually 1×-lobed or -parted; ultimate lobes 4-15 mm wide. Inflorescences 1-flowered; peduncle villous; involucral bracts 2-3, 1-tiered, simple, ± similar to terminal leaflets of basal leaves, obtriangular, 3-cleft, 0.5-2.5 cm, bases distinct, cuneate, margins crenate to broadly serrate, surfaces villous to nearly glabrous; segments 3, oblanceolate to obovate; lateral segments unlobed, 2-8 mm wide. Flowers: sepals 4-7, white or tinged blue or abaxially white, proximally blue, and adaxially white, broadly elliptic to ovate, (7-)8-20 × 4-9 mm, abaxially hairy, adaxially glabrous; stamens 70-80. Heads of achenes spheric; pedicel 4-18 cm. Achenes: body obovoid, 2-2.5 × ca. 1 mm, not winged, densely woolly; beak straight, 1-2.5 mm, glabrous. 2 n =16.
Plant 1-3 dm, mostly villous, from slender rhizomes; basal lvs long-petioled, deeply 3-parted into broadly cuneate-obovate segments, these crenately lobed or incised to above the middle into broad, usually obtuse divisions; involucral lvs sessile, otherwise much like the basal; peduncle solitary; sep 5-6, white or bluish, broadly oblong to oval or elliptic, 8-15 mm; fruiting head short-ovoid, 1 cm or less; achenes densely woolly; style short, glabrous; 2n=16. Wet, rocky ledges, usually in calcareous soil; Lab. to Alas., s. to Que., n. Minn., Colo., and Oreg.; n. Asia. June-Aug.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.