Culms trigonous, 15-60 cm, scabrous-angled. Leaves: sheath with apex of inner band yellowish, thickened, concave; ligules 1.5-2.2 mm; blades 1.5-4 mm wide. Inflorescences 2-8 cm; spikes 5-20, ascending, ovate; proximal spikes pistillate, the middle androgynous or staminate; terminal spike usually staminate. Pistillate scales reddish brown with green center and hyaline margins, ovate, 5-7.8 mm, usually longer than perigynia, apex acute to acuminate. Perigynia prominently thin-winged at apex, lanceolate to broadly ovate, (4-)4.5-6 × 1.3-3.3 mm; beak poorly defined, 1.2-2.5 mm. 2n = 58, 60-64, 64. Fruiting May-Jul. Maritime sand dunes and sandy, disturbed areas near the coast, 0-30 m; introduced; Del., Md., N.C., Oreg., Va.; Eurasia. Carex arenaria was first collected in North America in 1870; it remains quite local in distribution.