Plants perennial, tufted to mat-forming. Taproots filiform; rhi-zomes slender, 0.5-3 cm. Stems 25-60+, erect to ascending, green, 2-4 cm; internodes terete, 1-4 times as long as leaves, shiny, minutely glandular-villous. Leaves briefly connate basally, with herbaceous sheath 0.1-0.3 mm, sessile; blade obscurely 1-veined, narrowly elliptic to lanceolate or ovate, 2-6 × 1-1.5 mm, subsucculent, margins thickened, herbaceous, shiny, ciliate proximally, apex acute to apiculate, pustulate, glabrous; axillary leaf clusters absent. Inflorescences terminal, solitary flowers. Pedicels erect in fruit, 10-20 mm, densely glandular-villous. Flowers: sepals green, obscurely veined, not keeled, ovate (herbaceous portion ovate), 3.5-4 mm, not enlarging in fruit, apex acute to acuminate, not pustulate, minutely stipitate-glandular proximally; petals broadly elliptic, 2.5-3.5 mm, 11/ 1/ 2 times as long as sepals, apex rounded. Capsules tightly enclosed by calyx, ellipsoid, 4-5 mm, 1-1 1/5 times as long as sepals. Seeds 13-20, brown, reniform, compressed, 0.7-0.9 mm, shiny, rugulose (30×). 2n = 40, 80. Flowering spring-summer. Gravelly, moist, montane areas, open alpine woods; 50-1000 m; Alta., B.C., N.W.T., Yukon; Alaska; Asia. Arenaria longipedunculata was for many years included in A. humifusa.