Herbs, perennial, 4--13 dm. Rhizomes short -branched, forming distinct, often large clumps. Culms erect, terete, 1--2.5 mm diam. at top of sheaths. Cataphylls several. Leaves: blade absent. Inflorescences lateral, compound dichasia, many flowered; primary bract erect, terete, extending well beyond dichasium. Flowers: tepals tan or darker, usually with greenish midstripe, lanceolate, 1.9--3.5 mm; inner slightly shorter; stamens 3, filaments 0.5--0.8 mm, anthers 0.5--0.8 mm; style 0.2 mm. Capsules greenish tan or darker, 3-locular, broadly ellipsoid to oblate, 1.5--3.2 mm. Seeds amber, (0.3--)0.4---0.5 mm. 2n = 40, 42. Flowering summer, fruiting summer--fall. Swamps and their edges, marshes, moist meadows, and moist or saturated soils, often conspicuous in pasture meadows where it is shunned by grazing animals; Habitat??; 0--2500 m; B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que.; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Y., N.C., Ohio, Okla., Oreg., Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va., Wash., W.Va., Wis. The Juncus effusus complex has been variously recognized as containing several species or a single species with numerous infraspecific taxa. Unfortunately, North American treatments have dealt primarily with taxa in either the eastern or western portions of the continent. In considering the continent as a whole, little sense can be made of these treatments. The North American J. effusus complex is one that is in obvious need of modern systematic scrutiny.