Aerial shoots 10-35 cm, from rhizomes, rhizomes primarily vertical, occasionally strongly ascending. Basal leaves (0-)1-2, ternate; petiole 10-20 cm; terminal leaflet sessile, rhombic, lanceolate, or oblanceolate, (1.5-)2.5-6 × (1-)2-4 cm, base narrowly cuneate, margins coarsely serrate to coarsely dentate on distal 1/2-2/3, apex acuminate to narrowly acute, surfaces pilose or glabrous; lateral leaflets unlobed or sometimes 1×-lobed; ultimate lobes 10-19 mm wide. Inflorescences 1-flowered; peduncle coarsely pilose distally; involucral bracts 3, 1-tiered, ternate, ±similar to basal leaves, bases distinct; terminal leaflet sessile, rhombic, lanceolate, or oblanceolate, (1.5-)2-5.5(-7) × (0.6-)1-2.5 cm, base narrowly cuneate, margins coarsely serrate to coarsely dentate on distal 1/2-2/3, apex acuminate to narrowly acute, surfaces pilose or glabrous; lateral leaflets unlobed or sometimes 1×-lobed; ultimate lobes (5-)8-18 mm wide. Flowers: sepals 5-7, white, rarely pinkish, elliptic-obovate to ovate, (6-)8-20 × 6-8 mm, glabrous; stamens 35-55(-90). Heads of achenes nearly spheric; pedicel (1.5-)2-5 cm. Achenes: body ellipsoid to obliquely ovoid, 3-4 × 1.5-2 mm, not winged, villous; beak straight or slightly curved, 0.5-1 mm, glabrous or proximally minutely puberulous, not plumose.

Flowering spring-summer (Apr-Aug). Shaded, moist woods; 400-3000 m; B.C.; Idaho, Mont., Oreg., Utah, Wash.

Plants of Anemone piperi from southeastern Washington and northeastern Oregon (i.e., the westernmost limits of the species) are sometimes intermediate between A . piperi and A . oregana . Although they possess vertical rhizomes characteristic of A . piperi , they have the bluish or pinkish sepals of A . oregana . These plants are best referred to A . piperi , pending detailed biosystematic analysis.