Plants solitary or in small tufts, (5-)10-70 cm, clonal; rhizomes strongly present, stoloniferous. Culms leafiest toward base, ± trigonous, slender. Leaves: basal leaves spreading ascending, distal more erect, mostly exceeded by culms (except in high altitude forms); blades proximally flat or strongly folded, 1.5-4 mm wide, apex trigonous, subulate. Inflorescences: spikelet clusters (2-)3-5, compact, proximalmost widely spaced, turbinate to ovoid; peduncles ascending; branches ascending to spreading; leaf bracts exceeding proximalmost clusters, exceeded by distal cluster. Spikelets deep red brown to nearly black, ovoid, 3-4 mm, apex acute; fertile scales ovate, 2.5-3 mm, apex acute, midrib included or short excurrent. Flowers: perianth bristles 6, some short, some extending to or nearly to tubercle base, antrorsely barbellate. Fruits 2-3 per spikelet, 2-2.1 mm; body pale yellow brown, lenticular, broadly ellipsoid obovoid, 1.3-1.6 × 1-1.2 mm; surfaces transversely irregularly rugulose, intervals with rows of vertical, narrowly rectangular alveolae; tubercle evenly or concavely triangular, 0.5-0.6(-0.7) mm.

Fruiting late spring-summer. Marsh meadows, seeps, boggy sites; 1000-3500 m; Calif.; Mexico; South America (Colombia).