Plants: compact, short-branched and small; strongly reddish to golden brown, glossy when dry; flat-topped capitulum with moderately differentiated terminal bud. Stems: dark brown; superficial cortex of 3–4 layers of enlarged thin-walled cells. Stem: leaves lingulate,small, equal to or less than 0.8 mm, appressed to stem; apex with strong lacerate split in the middle; hyaline cells efibrillose, aporose, and nonseptate. Branches: strongly 5-ranked, short and blunt, not much elongated at distal end. Branch: fascicles with 2 spreading and 2–3 pendent branches. Branch: stems green, with cortex enlarged with retort cells. Branch: leaves ovate; usually less than 1.5 mm; stiff and slightly reflexed, straight to slightly subsecund; margins entire; hyaline cells moderately long and narrow (6–8:1), convex surface with one small round pore per cell at apex and numerous pseudopores on the margin, concave surface with large round wall thinnings in the cell angles and ends; chlorophyllous cells triangular in transverse section, with apex reaching concave surface. Sexual: condition unknown. Spores: not seen.
Common forming hummocks and carpets in a variety of weakly minerotrophic to ombrotrophic mires including Eriophorum tussock fens, dwarf shrub fens, polygon peatlands, string mires and raised bogs. low to moderate elevations. Greenland, Nfld. and Labr. (Nfld.), N.W.T., Nunavut, Que., Yukon, Alaska, Eurasia.
Sporophytes are rare in Sphagnum lenense. This species is easily distinguished from the similar S. lindbergii by its compact growth form and reddish brown color. Sphagnum lenense also is a hummock former in the tundra whereas S. lindbergii forms carpets.