Plants perennial, tufted or becom-ing cespitose in alpine habitats, glabrous. Stems ascending or sometimes pro-cumbent, few- to many-branched, not filiform. Leaves: axillary fascicles absent; basal frequently in primary and secondary rosettes 9-45 mm diam., blade linear, 10-20 mm, not succulent, apex apiculate, rarely aristate, glabrous; cauline not conspicuously connate basally, rarely forming inflated cup in cespitose, alpine plants, blade linear, sometimes linear-subulate in cespitose plants, 4-20(-25) mm, not fleshy, apex apiculate, glabrous. Pedicels frequently recurved during capsular development, erect in fruit, filiform, glabrous. Flowers axillary or terminal, 5-merous, very rarely some 4-merous; calyx base glabrous; sepals elliptic, 2-2.5 mm, hyaline margins white, rarely purple in alpine specimens, apex obtuse to rounded, remaining appressed following capsule dehiscence; petals elliptic, (1-)1.5-2 mm, shorter than or equaling sepals; stamens (5 or) 10. Capsules 2.5-3(-3.5) mm, 1.5-2 times sepals, dehiscing to base. Seeds brown, obliquely triangular with distinct abaxial groove, 0.3-0.4 mm, smooth to slightly pebbled. 2n = 22.

Flowering mid-late summer. Montane sites, open or light shade, wet places on lake margins, along stream gravels and seepages in rock ledges and roadcuts, subalpine and alpine zones; 1000-4000 m; Greenland; Alta., B.C., Nfld. and Labr. (Nfld.), N.W.T., Nunavut, Que., Yukon; Alaska, Ariz., Calif., Colo., Idaho, Mont., Nev., N.Mex., Oreg., Utah, Wash., Wyo.; Mexico; Eurasia.

Some specimens from alpine habitats in Montana and Alberta are intermediate between Sagina saginoides and the typically arctic S. nivalis.