Nasturtium obtusum Nuttall var. alpinum S. Watson, Botany (Fortieth Parallel), 15. 1871; Radicula alpina (S. Watson) Greene; Rorippa curvipes Greene var. alpina (S. Watson) Stuckey; R. obtusa (Nuttall) Britton var. alpina (S. Watson) Britton

Perennials; (terrestrial or of wet habitat, not submerged, caudex branched or simple, well-developed); usually glabrous. Stems usually decumbent to prostrate, rarely erect, much-branched basally and distally, (0.3-)0.4-1.9(-2.6) dm (rarely pilose basally). Basal leaves not rosulate; [petiole (0.3-)0.9-2(-2.5) cm]; blade [(0.6-)1-3.2(-4) cm × (2-)3-8(-15) mm], margins usually dentate to pinnatifid, rarely repand. Cauline leaves petiolate or subsessile; blade obovate to oblanceolate, smaller distally, base cuneate, attenuate, not auriculate, margins entire, crenate, or repand. Racemes elongated. Fruiting pedicels ascending to horizontal or slightly reflexed, straight or curved, (2-)3-6(-8) mm. Flowers: sepals ascending, oblong, 1-1.7(-2) × 0.6-0.8 mm; petals yellow, spatulate, (1.3-)1.5-2 × 0.5-0.8 mm; median filaments 0.8-1.2 mm; anthers ovate, 0.3-0.4 mm. Fruits often siliques, sometimes silicles, straight or slightly curved, oblong to lanceolate or ovoid, 3-7 (-8) × 1.4-2.1(-2.7) mm; valves glabrous; ovules 26-42 per ovary; style (0.3-)0.5-1(-1.2) mm. Seeds biseriate, yellow-brown, ovoid to subglobose, 0.5-0.7 mm (0.4-0.5 mm diam.), reticulate. 2n = 16.

Flowering Jun-Sep. Lakeshores, pond margins, streamsides, dried snow ponds, meadows, seep areas; 1400-3800 m; Colo., Idaho, Mont, Nev., Utah, Wyo.