Herbs, perennial, cespitose; rhizomes knotty, much branched, 2-5 mm diam., scaly. Culms roundly trigonous, basally with dark fibrous remnants of old leaf sheaths, (0.5-)4-30 cm × 0.4 -1.1 mm, glabrous. Leaves 1-5, flat, involute toward apex, 3-18 cm × 1-2.5(-3) mm. Inflorescences: heads hemispheric to spheric, (3-)6-15(-24) mm diam.; rays absent; bracts 2-5, horizontal to reflexed, parallel to culm, 1-13 cm × 1-3 mm, margins and keel sparsely minutely scabridulous distally. Spikelets (5-)20-60(-100), whitish to greenish or brownish, ovoid to oblong-lanceoloid, compressed, 3-7 × 2-4 mm; floral scales (8-)10-12(-24), laterally milky white (infrequently yellowish, pale greenish, brown, or bronze-white), medially green or white, laterally ribless, medially 3-ribbed, ovate to ovate-lanceolate, 1.6-3(-3.4) × 0.8-1.3 mm, apex mucronate to acuminate. Flowers: stamens 3; anthers linear, (0.4-)0.6-0.8(-1.1) mm, connective not prolonged; styles 0.8-1.8 mm; stigmas (0.5-)1-1.5(-2) mm. Achenes brown to blackish, trigonous, broadly obovoid, 0.5-1 × 0.3-0.75 mm, base slightly stipelike, ± cuneate to rounded, apex apiculate, papillose. Fruiting summer. Seeps, damp meadows in montane forests; 1000-2000 m; Ariz., Tex.; Mexico; Central America (Honduras); South America.