Plants small to moderate-sized, slender, fairly stiff but soft, capitulum flat-topped and stellate; deep maroon-red to variegated red and yellowish green, lacking metallic sheen when dry. Stems red, yellowish or pale green; superficial cortical cells aporose. Stem leaves lingulate-triangular to lingulate, 1-1.4 mm, apex broadly rounded but becoming acute in hemiisophyllous forms, border strongly developed at base (more than 0.25 width); hyaline cells rhombic and 0-3-septate with some cells in leaf midregion 2-septate. Branches weakly to strongly 5-ranked. Branch fascicles with 2 spreading and 1-2 pendent branches. Branch leaves ovate to ovate-lanceolate, 0.9-1.2 mm, concave, subsecund on some branches, apex involute; hyaline cells on convex surface with numerous round to elliptic pores along the commissures, grading from small round pores near apex to round pores near base, on concave surface with large round pores in proximal portions of leaf. Sexual condition dioicous. Spores 18-33 µm, coarsely papillose on both surfaces; proximal laesura less than 0.4 spore radius.
Sporophytes are uncommon in Sphagnum rubellum. This common species is associated with S. angustifolium, S. capillifolium, S. fallax, S. fuscum, S. magellanicum, S. papillosum, S. recurvum, and S. tenellum. Inland, it has a greater tendency to form extensive carpets and floating mats than hummocks. See also discussion under 65. S. andersonianum, 68. S. bartlettianum, and 86. S. talbotianum.