Plants perennial, cespitose to mat-forming. Taproots stout, woody. Stems erect, green, 1-12 cm, trailing stems 2-20+ cm, stipitate-glandular, internodes of flowering stems 1-6 times as long as leaves. Leaves tightly overlapping (vegetative), variably spaced (cauline), usually connate proximally, with tight, scarious to herbaceous sheath 0.3-1.5 mm; blade straight to outwardly curved, green, 3-angled, 3-veined abaxially, midrib prominent, lateral veins weak in distal 3, needlelike to subulate, 1-8 × 0.4-1 mm, flexuous, margins not thickened, herbaceous, sometimes finely ciliate, apex green, rounded to acute, often apiculate, somewhat navicular, shiny, glabrous; axillary leaves present among vegetative leaves. Inflorescences solitary flowers, terminal, or occasionally in 2-3-flowered, open cymes; bracts subulate, herbaceous. Pedicels 0.3-1.5 cm, stipitate-glandular. Flowers: hypanthium cup-shaped; sepals prominently 3-veined proximally, narrowly ovate to oblong (herbaceous portion lanceolate to oblong), 2.9-6.5 mm, not enlarging in fruit, apex often purple, narrowly rounded, hooded; petals ovate to spatulate, 1.2-2 times as long as sepals, apex rounded, entire. Capsules narrowly ellipsoid, 3.5-6 mm, equaling sepals. Seeds reddish tan, suborbiculate with radicle prolonged into beak, somewhat compressed, 0.6-0.7 mm, obscurely sculptured (50×). 2n = 26, ca. 52, 78. Flowering summer. Dwarf willow communities, fell-fields, snow beds in subalpine and alpine areas; 0-4000 m; Alta., B.C., N.W.T., Yukon; Alaska, Ariz., Calif., Colo., Idaho, Mont., Nev., N.Mex., Oreg., Utah, Wash., Wyo.; Asia (Russian Far East). Minuartia obtusiloba, an amphi-Beringian species, sometimes forms hybrid swarms with M. arctica. Specimens labeled Arenaria sajanensis Willdenow ex Schlechtendal from western North America, sometimes referred to M. biflora (e.g., H. J. Scoggan 1978-1979, part 3), are likely to be M. obtusiloba.

Plant: Perennial, cespitose to mat-forming, 1-12 cm, green, glandular-hairy; taproot > 3 mm diam; stem in flower ± erect; trailing stem 2-20+ cm Leaves: simple, opposite, 1.5-8 mm, 0.4-1 mm wide, > internodes, needle- to awl-shaped, ± straight, flexible, ± evenly spaced; axillary leaves well developed INFLORESCENCE: cyme, terminal or axillary; flowers 2-many, open to ± dense, or flower solitary; peduncles and pedicels 0.5-35+ mm Flowers: hypanthium short, obscure; sepals 5, ± free, 2.9-4 mm, narrowly rounded; margin incurved, hood-like, ribs generally 3; petals 1.2-1.5 X sepals; stamens arising from an obscure to prominent disk; styles 3, 0.3-2 mm Fruit: Fruit: capsule, narrowly ovoid to widely elliptic; teeth 3, ascending to recurved; Seed 0.6-0.7 mm; margin thick, reddish tan Misc: Among dwarf willows, unglaciated granitics and metamorphics, alpine; 3150-3700 m.