Cardamine digitata Richardson, Bot. App. Frankl. Narr. Journey Polar Sea 743. 1823, not C. digitata (Lamarck) O. E. Schulz (1903). TYPE:

Cardamine digitata var. oxyphylla Tratvetter; C. hyperborea var. oxyphylla (Trautvetter) O. E. Schulz, Bot. Jahrb. Syst. 32: xxx. 1903. TYPE:

C. hyperborea O. E. Schulz, Bot. Jahrb. Syst. 32: 550. 1903. TYPE:

C. richardsonii Hultén, Acta Univ. Lund. N. F., Adv. 2, 41 (Fl. Alaska & Yukon): 838. 1945. TYPE:

Herbs, perennial, glabrous throughout. Rhizomes slender, cylindrical, 0.5–1.5 mm in diam.; stolons absent. Stems (0.6–)1–2(–3) dm, erect, simple, glabrous. Rhizomal leaves pinnately 5–7-foliolate, not fleshy, (2–)4–10 cm; petiole (1.5–)3–7(–9) cm; terminal leaflet linear to narrowly oblong or narrowly lanceolate, (0.5–)1–2.5(–3.3) cm × 0.5–4(–8) mm, sessile, glabrous, base cuneate to attenuate, margin entire; lateral leaflets about as large as or smaller than terminal leaflet, similar in other aspects; cauline leaves (1 or)2 or 3, 5–7-foliotate, alternate; petiole (2–)5–12(–15) mm, base not auriculate; terminal leaflet narrowly lanceolate to linear, 1–3.2(–4) cm × 0.5–2.5(–3.5) mm, sessile, base cuneate to attenuate, margin entire, apex acute to acuminate; lateral leaflets similar to terminal one but smaller, sessile. Racemes ebracteate; fruiting pedicels suberect to divaricate-ascending, (0.7–)1–2.5 cm. Sepals ovate, 2.5–3.5 × 1.5–2.5 mm, erect, base of lateral pair not saccate; petals white, obovate, 5–9 × 2.5–5 mm, clawed, apex rounded; median filament pairs 3–4.5 mm, lateral pair 1.5–2.5 mm; anthers oblong, 1–1.5 mm. Fruit linear, (1.5–)2–4 cm × 1.5–2 mm; valves glabrous; style (1–)1.5–2.5(–4) mm; ovules and seeds 6–12 per fruit. Seeds brown, oblong, 1.5–2.2 × 0.9–1.1 mm. 2n = 28, 42.

Flowering: Jun–Aug.

Habitat: damp flats, river banks, tundra, meadows, bluffs, hummocks, sandy beaches, slopes, mossy mats, sedge swales.

Elevation: 0 –1400 m.

Distribution: Canada (Northwest Territories, Yukon), Russia (Siberia, Far East), United States (Alaska).