Plants small, slender, often wiry; green, yellow-brown or golden-brown; capitulum small with terminal bud absent. Stems light brown to dark brown; superficial cortex of1 layer of enlarged thin-walled cells. Stem leaves triangular-lingulate, 0.8 mm or less; apex entire or weakly denticulate, hyaline cells sometimes septate, efibrillose and aporose except near apex. Branches often short and blunt. Branch fascicles with 2--3 spreading and 2--3 pendent branches Branch leaves broadly ovate, subsecund, hyaline cells on convex surface with very numerous small pores (18--40 per cell) in a continuous row along the commissures, concave surface usually aporose. Sexual condition dioicous. Capsules exserted, with few pseudostomata. Spores 30--35 µm; finely papillose on both surfaces, distinct bifurcated Y-mark sculpture on distal surface; proximal laesurae more than 0.5 spore radius.

Minerotrophic, near the edges of open, poor fens, less commonly found in open medium fens; Alta, B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., Que., Yukon; Alaska, Calif., Colo., Conn., Idaho, Ill., Ind., Maine, Mass., Mich., Minn., Mont., N.H., N.J., N.Y., Ohio, Oreg., Pa., R.I., Vt., Wash., Wis., Wyo.; Eurasia.

Sporophytes are rare. Sphagnum subsecundum is often associated with S. angustifolium,S. centrale, S. fimbriatum, S. flexuosum, S. palustre, and S. teres. The most widespread and common of the sect. Subsecunda, this species also exhibits considerable phenotypic plasticity in size. However, the stem leaves are always quite small in comparison to similar species. See also discussions of S. contortum, S. inundatum and S. subobesum.