Herbs, annual, cespitose, with roots fibrous. Culms trigonous, glabrous. Leaves V-shaped to flat, (2-)4-11 cm × 3-4 mm. Inflorescences: rays absent; bracts 2-4, ± horizontal, flat, 1-6.5 cm × 2-3 mm; rachilla persistent, wingless. Spikelets 10-40, compressed, ovoid to linear-lanceoloid, quadrangular, 5-9 × 2-3 mm; floral scales deciduous, 5-20, spreading, pale greenish to reddish brown, laterally (5-)7-9(-13)-ribbed, ovate, 3-4 × 1-2 mm, apex straight, excurved mucronate, or cuspidate. Flowers: stamens 1-2; filaments 1.5 mm; anthers 0.8-1 mm, connective apex reddish yellow, less than 0.1 mm; styles 0.8-1 mm; stigmas 1-1.2 mm. Achenes brown to reddish brown, broadly ellipsoid to obovoid, 0.8-1.2 × 0.5-0.6 mm, base ± cuneate, apex truncate-obtuse, surfaces puncticulate.

Fruiting summer. Thin soil over outcrops of granite or sandstone of the Piedmont and inner coastal plain; 50-400 m; Ala., Ga., N.C., S.C., Tenn., Va.

Cyperus granitophilus is documented as an autotetraploid derivative of C. squarrosus (L. W. Garoni and W. H. Murdy 1964).