Herbs, perennial, strongly rhizomatous, 1--4 dm. Culms solitary, 1--2 mm diam. Cataphylls 1--2. Leaves partially cauline, 3--5, auricles absent distally, rounded proximally; blade channeled, to 20 cm, reduced distally. Inflorescences glomerules, 1--3(--5), each with 2--10 flowers; peduncles 0.4--1.5 cm; primary bracts somewhat inflated, usually surpassing inflorescence. Flowers: bracteoles absent; tepals brown or occasionally paler, lanceolate, 4.5--6.6 mm, apex acute to obtuse; inner series slightly shorter; stamens 6, filaments 2.5--3.5 mm, anthers 0.6--1.3 mm; style 1--1.3 mm. Capsules chestnut brown, 3-locular, narrowly oblong, 6.5--8.5 x 1.8--2.3 mm. Seeds pale yellow, fusiform, body 0.6--0.7 mm, tails 0.8--1.1 mm. 2n = 60, 90, 120.

Flowering and fruiting late spring--summer. Tundra, subalpine and alpine bogs and meadows, and along streams in gravelly or clayey soils; 10--3700 m; Greenland; Alta., B.C., Man., Nfld. and Labr. (Labr.), N.W.T., Nunavut, Ont., Que., Sask., Yukon; Alaska, Colo., Mont., Nev., N.Mex., Utah, Wyo.; Europe; Asia.

In southern Alaska some plants with several many-flowered heads and capsules about double the length of the perianth have been referred to the Asian Juncus castaneus subsp. leucochlamys. The distinction, however, seems dubious without further investigation.