Plants moderate-sized, fairly stiff-stemmed; green, brownish green, pale yellow, golden yellow, yellow and brown; capitulum hemispherical and not 5-radiate to somewhat 5-radiate in shade-grown or wet-grown forms. Stems pale green to pale brown, superficial cortex of 2 layers of moderately differentiated cells. Stem leaves triangular to lingulate-triangular, 0.8-1.2 mm, mostly appressed to the stem, apex acute to apiculate, hyaline cells mostly efibrillose and nonseptate. Branches straight, mostly unranked, but can be 5-ranked in wet-growing forms, leaves little elongated at distal branch ends. Branch fascicles with 2 spreading and 2-3 pendent branches. Branch stems green but proximal end sometimes red, with cortex enlarged with conspicuous retort cells. Branch leaves ovate-lanceolate, greater than 1.2 mm, straight, undulate and sharply recurved when dry, margins entire; hyaline cells on convex surface with usually 1 round pore per cell at apical end, on concave side with round wall thinnings in the cell ends and angles; chlorophyllous cells triangular and just reaching or slightly enclosed within the concave surface. Sexual condition dioicous. Spores 25-31 µm; proximal surface finely papillose, distal surface pusticulate with bifurcated Y-mark sculpture; proximal laesura less than 0.5 spore radius.
Widespread in poor fen habitats, often as a pioneer species in extensive mats, occasionally in ombrotrophic mires at hummock bases; low to moderate elevations; N.B., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que.; Conn., Del., Ill., Ind., Maine, Mass., Mich., Minn., N.H., N.J., N.Y., N.C., Ohio, Pa., Tenn., Vt., Va., W.Va.; Europe.
Sporophytes are uncommon, capsules mature early to mid summer.
Sphagnum fallax can be distinguished from the closely related S. isoviitae by its sharply recurved branch leaves, as opposed to the leaves of the latter only slightly reflexed at their tips. See also discussion under 26. S. brevifolium and 46. S. splendens.