Plants colonial; rhizomes long-creeping. Culms central, slender, trigonous, 25-60 cm, papillose and scabrous-angled distally. Leaves: basal sheaths brown, bladeless, rapidly disintegrating into fibers; ligules 0.7-1.5 mm, wider than long; blades somewhat glaucous, M-shaped, 1.5-3.2 mm wide, papillose abaxially. Inflorescences 2.5-12 cm; rachis beyond proximal pistillate spikes sharp-angled, often finely scabrous; proximal (1-)2-3(-4) spikes pistillate, not or barely overlapping, ascending; distal spikes erect; terminal 1 spike staminate. Pistillate scales ovate to broadly ovate, apex acute to acuminate-awned, awn to 1.3 mm, glabrous. Perigynia ascending, essentially veinless except for 2 marginal veins, ovoid, 3.1-4.5 × 1.7-2.5 mm, glabrous; beak 0.4-0.8 mm, bidentulate, teeth straight, 0.2-0.3 mm.

Fruiting Jun-Jul. Dry, open or lightly shaded areas; 200 m; introduced; Ill.; e Asia.

Carex heterostachya is a rare introduction from eastern Asia; first discovered in 1949, it is still extant and slowly spreading at its only known North American location (A. A. Reznicek 1994).