Plants moderate-sized to robust, strong-stemmed, lax to somewhat compact, capitulum somewhat flattened to more typically compact and rounded; green to golden brown to pale brown with often a pinkish tinge; carpets to more or less compact, low to moderate sized hummocks. Stems brown, superficial cortical cells with spiral reinforcing fibrils visible, usually 2--4 pores per cell, comb-fibrils lacking on interior wall. Stem leaves to 1.7 ´ 1 mm, occasionally longer; rarely hemiisophyllous; hyaline cells non-ornamented, nonseptate. Branches long and tapering, leaves ± imbricate to spreading in shade forms. Branch fascicles with 2 spreading and 2 pendent branches. Branch stems with hyaline cells non-ornamented; no or weak funnel-like projections on the interior end walls, often with 1 large pore per cell on superficial cell walls. Branch leaves broadly ovate, 2.2 ´ 1.3 mm, hyaline cells non-ornamented, convex surface with elliptic pores along the commissures, chlorophyllous cells isosceles-triangular to ovate-triangular in transverse section and just enclosed to just exposed on the convex surface; end wall not thickened. Sexual condition dioicous. Capsules with numerous pseudostomata. Spores 24--33 µm, surface finely papillose to smooth, distal surface with distinct bifurcated Y-mark sculpture; proximal laesura more than 0.60 spore radius.

Capsules mature mid- to late summer. Widespread in forested fens and poor to rich sedge fens; B.C., N.B., Nfld., N.S., Ont., Que., P.E.I.; Ala., Ark., Calif., Conn., Del., Fla., Ga., Ill., Ind., Iowa, Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Okla., Oreg., Pa., S.C., Tenn., Tex., Vt., Va., W.Va., Wash., Wis.; Europe.

This species may occur elsewhere, but the taxonomy is unclear. In some open-grown situations, S. palustre may have a reddish tinge that may seem similar to S. magellanicum, but this is a pinkish red rather than the purplish red of the latter. See under S. henryense and S. papillosum for distinction from those species.