Thlaspi arcticum A. E. Porsild, Sargentia 4: 40. 1943

Perennials; (with persistent petiolar remains). Stems simple or several from caudex, erect, unbranched, 0.5-1.8 dm. Basal leaves: petiole 0.4-1.3 cm; blade oblanceolate to spatulate, 0.3-1.8 cm × 2-4 mm, base cuneate or attenuate, margins entire, apex obtuse. Cauline leaves 3-7; blade ovate or suboblong, 0.5-1 cm × 1-5 mm, base minutely auriculate, margins entire, apex obtuse to subacute. Racemes 0.5-6 cm. Fruiting pedicels ascending to horizontal, straight, 3-8 mm. Flowers: sepals 1.5-2.5 × 0.5-1 mm, (margins white); petals white, 3-5 × 2-2.5 mm, often flaring between blade and claw, apex rounded; filaments 2-3 mm; anthers ca. 0.5 mm. Fruits not winged, narrowly obovate, 6-10 × 2-3.5 mm, base cuneate, apex obtuse; ovules 8-14 per ovary; style (0.3-)0.6-1 mm. Seeds yellow-brown, 1.5-2 mm, nearly smooth. 2n = 14.

Flowering Jun-Aug. Dry tundra ridges, arctic coast; 0-500 m; Yukon; Alaska.

Noccaea arctica is rare, known from a limited number of collections. P. K. Holmgren (1971) suggested that additional collections might indicate that it is a variety of N. fendleri (as Thlaspi montanum).