Plants colonial, long-rhizomatous. Culms 30-60 cm, scabrous to smooth distally. Leaves: proximal sheaths fibrillose, bladeless, brown- to reddish purple tinged, 2-4.5 mm diam.; ligules 2-10 mm, longer than wide; largest blades green, flat, 4-45 cm × 2.5-6 mm. Inflorescences 6-19 cm, 1.4-2.2 times longer than proximal bract; proximal bracts 2-9 cm; sheath 0.6-2 cm, blade 1.5-7 cm; proximal spikes pistillate or androgynous; lateral spikes cylindric, 1.5-3.5 cm × 7.5-11 mm; terminal 1-3 spikes, staminate. Pistillate scales purple or brown, apex rounded or obtuse. Perigynia densely arranged, green to light brown, 2-ribbed and finely veined, 4.2-6.8 × 1.5-2.5 mm, with low, broad papillae; beak purple tinged, mouth hyaline, obliquely bidentate, asymmetrically flared, 0.8-1.8(-2.2) mm. Achenes light to dark brown, 2.2-2.8 × 1.4-2.3 mm. Fruiting early-mid summer. Thin woods with sandy soils; of conservation concern; 30-1200 m; Conn., Del., Maine, Md., Mass., N.H., N.J., N.Y., Pa., R.I., Va., W.Va. Carex polymorpha, rare throughout its range, is of conservation concern (L. A. Standley and J. L. Dudley 1991).