Herbs, perennial, cespitose, bases cormose; rhizomes knotted, beaded. Culms trigonous, 15-48 cm × 0.4-1 mm, glabrous. Leaves flat, 10-30 cm × 0.5-2 mm. Inflorescences: spikes rather densely ovoid, 1-3.5 cm; rays 0 (sometimes 1-4), 1-6 cm; rachis 1-4 mm; bracts 3-4, horizontal to slightly reflexed, flat, 6-25 cm; rachilla ± deciduous, wingless. Spikelets 25-60, compressed, oblong-lanceoloid, 5-12 × 2.2-3.5 mm; floral scales deciduous, 5-15, yellowish to yellowish brown, laterally 4-5-ribbed, oblong-ovate, 2.6-3.6 × 1.4-2 mm, margins loosely spreading or clasping achene. Flowers: anthers 0.8-1 mm; styles 1 mm; stigmas 1.5-2.5 mm. Achenes dark grayish brown, sessile, narrowly oblong, 1.8-2.2 × 0.5-0.8 mm, apex obtuse, apiculate, surfaces puncticulate. Fruiting summer. Well-drained, open roadsides, fields, pine barrens, dunes; 0-200 m; Ala., Fla., Ga., La., Md., Miss., N.C., S.C., Tex., Va. Cyperus filiculmis has long been treated within a broader and more widely used concept of C. filiculmis (C. lupulinus); see B. G. Marcks (1974)