Sphagnum contortum Schultz, Prodr. Fl. Starg. Suppl. 64. 1819.
Authors: Richard E. Andrus
Plants moderate to small-sized, weak-stemmed to spawling; green, yellow-green to golden-brown; capitulum usually large and flat with curved branches; green, yellow-green, or golden brown. Stems pale green to light brown, rarely dark brown; superficial cortex of 2--3 layers of enlarged, thin-walled cells. Stem leaves triangular-lingulate to lingulate, 0.7--1.4 mm; apex rounded-obtuse and weakly denticulate; hyaline cells nonseptate, mostly efibrillose, and, if porose, with more pores per cell on the concave surface (3--6) than on the convex surface (0--2). Branches somewhat curved, leaves spreading. Branch fascicles with 2--3 spreading and 2--3(4) pendent branches. Branch leaves ovate to ovate-lanceolate, 1.2--2 mm; subsecund; hyaline cells with numerous tiny pores in a continuous line along the commissures on the convex surface, no or scattered pores on the concave surface; Sexual condition dioicous. Capsules exserted, with scattered pseudostomata. Spores 22--28 µm; papillose on both surfaces; proximal laesurae more than 0.5 spore radius.
Very minerotrophic, sometimes found in slightly basic mires; intolerant of shade; Alta., B.C., Nfld., N.S., Ont., Que.; Alaska, Cal., Colo., Conn., Idaho, Ill., Ind., Maine, Md., Mass., Mich., Minn., N.H., N.J., N.Y., N.C., Ohio, Ore., Pa., R.I., Vt., Wash., Wis., W.Va.; Eurasia.
Sporophytes are rare. This species is often associated with S. warnstorfii, S. centrale, Campylium stellatum, and Calliergonella cuspidata. The relatively small size, curved capitulum branches and loosely spreading, subsecund branch leaves separate this species out along with S. subsecundum. Compared to the latter species, S. contortum has narrower branch leaves and a larger stem leaf$ but field distinction can be difficult. See also discussion of S. platyphyllum.