Aerial shoots 5-20(-30) cm. Basal leaves: lateral leaflets usually 1×-lobed; ultimate lobes 6-10 mm wide. Inflorescences: involucral bracts with terminal leaflet 1-4 × 0.8-2.5 cm, base narrowly cuneate, margins serrate, more sharply serrate than in basal leaves, apex acuminate to narrowly acute; lateral leaflets usually 1×-lobed; ultimate lobes 4-10 mm wide. Flowers: sepals abaxially reddish, violet, or marginally purple, adaxially white; stamens 60-75. Achenes: body puberulous to pilose.

Flowering spring (Apr-Jun). Marshes, sphagnum bogs; of conservation concern; 300-1000 m; Oreg., Wash.