Cardamine digitata var. oxyphylla Trautvetter; C. hyperborea O. E. Schulz; C. hyperborea var. oxyphylla (Trautvetter) O. E. Schulz; C. richardsonii Hultén

Perennials; glabrous throughout. Rhizomes cylindrical, slender, 0.5-1.5 mm diam. Stems erect, unbranched, (0.6-)1-2(-3) dm. Rhizomal leaves pinnately 5 or 7-foliolate, (2-)4-10 cm, (not fleshy), leaflets sessile; petiole (1.5-)3-7(-9) cm; lateral leaflets similar to terminal, blade sometimes smaller; terminal leaflet blade linear to narrowly oblong or narrowly lanceolate, (0.5-)1-2.5(-3.3) cm × 0.5-4(-8) mm, base cuneate to attenuate, margins entire. Cauline leaves (1 or) 2 or 3, 5 or 7-foliolate, petiolate, leaflets sessile; petiole (0.2-)0.5-1.2(-1.5) cm, base not auriculate; lateral leaflets similar to terminal, blade smaller; terminal leaflet blade narrowly lanceolate to linear, 1-3.2(-4) cm × 0.8-2.5(-3.5) mm, base cuneate to attenuate, margins entire (apex acute to acuminate). Racemes ebracteate. Fruiting pedicels suberect to divaricate-ascending, (7-)10-25 mm. Flowers: sepals ovate, 2.5-3.5 × 1.5-2.5 mm, lateral pair not saccate basally; petals white, obovate, 5-9 × 2.5-5 mm (clawed, apex rounded); filaments: median pairs 3-4.5 mm, lateral pair 1.5-2.5 mm; anthers oblong, 1-1.5 mm. Fruits linear, (1.5-)2-4 cm × 1.5-2 mm; ovules 6-12 per ovary; style (1-)1.5-2.5(-4) mm. Seeds brown, oblong, 1.8-2.2 × 0.9-1.1 mm. 2n = 28, 42.

Flowering Jun-Aug. Damp flats, stream banks, tundra, meadows, bluffs, hummocks, sandy beaches, slopes, mossy mats, sedge swales; 0-1400 m; N.W.T., Yukon; Alaska; ne Asia (Russian Far East, Siberia).