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 × 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.
Phenology: Flowering and fruiting late spring–summer.
Habitat: Tundra, subalpine and alpine bogs and meadows, and along streams in gravelly or clayey soils
Elevation: 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.