Plants highly variable in size and habit but usually rather tall and robust. Stems (2-)5-10(-70) cm. Leaves loosely imbricate to rather distant; sheath clasping the stem and usually plainly visible wet or dry; blade typically divergent and sharply toothed to the base; marginal cells of lamellae in section broader than those beneath, retuse to distinctly notched, with prominent knobs; perichaetial leaves not markedly longer than the foliage leaves, ending in a short, roughened spinulose tip. Capsule short-rectangular.
Moist organic soil in wet habitats, pastures, old fields, and meadows, peatlands, margins of bogs or swamps, often covering extensive areas, low to moderate elevations, widespread in the boreal forest; rare north of the tree line and absent from the high Arctic (D. G. Long 1985); Greenland; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Ark., Calif., Colo., Conn., Del., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., N.H., N.J., N.Y., N.C., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W. Va., Wis., Wyo.; n, c Europe; n, e Asia; n Africa; Atlantic Islands (Macaronesia); Pacific Islands (Hawaii, New Zealand); Australia.
Plants in compact, rather dense tufts. Stems to 6 cm. Leaves densely imbricate and crowded, somewhat less sharply toothed than in var. commune; marginal cells of lamellae in section narrow, more shallowly grooved; peri-chaetial leaves conspicuous and ribbon-like, exceeding the foliage leaves, mostly hyaline, subentire, ending in a long, nearly smooth awn. Capsule short-rectangular to cubic.
Variety perigoniale has a distinctly 'bushy' aspect, the leaves thick set and densely imbricate. The typical expression is common on the Atlantic coastal plain, as in the Pine Barrens of New Jersey (the type was from Carolina). Elsewhere, its distribution and ecology are poorly documented, but it is probably not simply a dry land phase (H. A. Crum and L. E. Anderson 1981), occurring sporadically throughout the range of the species. The perichaetial leaves are not only longer than the foliage leaves, but distinctly ribbon-like, irregularly twisted and curled when dry.