Herbs, perennial, rhizomatous, 0.4--5.5(--7) dm. Rhizomes with swollen nodes, 1 mm diam. Culms erect, terete, 1--3 mm diam., smooth. Cataphylls 0 or 1--2., pink to gray, apex acute. Leaves: basal 1, cauline 2--4, green to pink; auricles 0.5--1.7 mm, apex rounded, membranaceous to cartilaginous; blade terete, 6--30 cm x 0.5--1.5 mm. Inflorescences terminal racemes of 3--15 heads, 0.6--6 cm, branches ascending to erect; primary bract erect; heads 6--30-flowered, spheric, 6--10(--12) mm diam. Flowers: tepals green to light brown, lance-subulate, 2.4--4.1 mm, nearly equal, apex acuminate; stamens 3 or 6, anthers 1/2 to equal filament length. Capsules exserted, chestnut brown, 1-locular, lance-subulate, 3.2--5 mm, apex tapering, valves separating at dehiscence, fertile throughout or only proximal to middle. Seeds oblong, ellipsoid, or obovoid, 0.4--0.5 mm, not tailed. . 2n = 40. Fruiting early summer--fall. Sandy and muddy shores of lakes, streams, rivers, and estuaries (both freshwater and brackish), swamps, fens, salt marshes, and wet fields, often calcareous; 0--2200 m; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Ariz., Calif., Colo., Conn., Del., Idaho, Ill., Ind., Iowa, Kans., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.Dak., Ohio, Okla., Pa., R.I., S.Dak., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Mexico (s to Puebla). The Texas populations and some of the northern Mexican populations consistantly have 3 stamens. These populations have been separated as Juncus nodosus var. meridionalis. Plants with 3 stamens are found elsewhere, however, and other significant characters do not appear to separate these populations.