Plants cespitose; rhizomes short or inconspicuous. Culms trigonous in cross section, 40-120 cm, smooth distally. Leaves: basal sheaths reddish purple; ligules as wide to slightly longer than wide; blades dark green, flat to W-shaped, 2-5 mm wide, glabrous. Inflorescences 10-35 cm; proximal bract 25-70 cm, exceeding inflorescence; proximal (1-)2-3(-4) spikes pistillate, erect or the proximal spreading or pendent, cylindric; terminal 1-3 spikes staminate. Pistillate scales narrowly ovate, 3.9-5.2 × 1.2-2.4 mm, shorter than perigynia, margins entire, apex acute, awnless. Perigynia ascending, often green or straw colored, strongly 7-12-veined, veins running to beak, broadly elliptic, 7.5-12.5 × (4-)4.5-7 mm, apex contracted; beak 2.4-4.8 mm, smooth, bidentate, teeth straight, 0.7-1.9 mm. Stigmas 3. Achenes brown, trigonous, asymmetric, deeply indented on 1 face, smooth. Fruiting Jun-Aug. Deciduous swamp forests, thickets, often along streams or pond shores, wet meadows; 0-500 m; N.B., Ont., Que.; Conn., Ind., Maine, Md., Mich., Minn., N.Y., Ohio, Pa., Vt., Wis.
From Flora of Indiana (1940) by Charles C. Deam
Frequent in northeastern Indiana; otherwise known in the state only from the dune area and from Floyd County. It is found in swales in woods, swamps, and on borders of ponds, frequently in shallow water.
Much like no. 216 [Carex vesicaria L.]; stems 4-8 dm, tufted on short rhizomes; lvs soft and flat, the main ones 2-4 dm נ3-6 mm; staminate spikes usually 2, widely separated, much elevated above the pistillate, these 2-4, well separated, cylindric, 2-5 cm; perigynia numerous, imbricate and ascending in ca 6 rows, 7-10 נ(4-)4.5-7 mm, inflated and very thin-walled, broadly ovoid, the conic summit tapering into a slender beak 2 mm, its teeth 0.5-1 mm; achene trigonous, obovoid, 3-4 mm, deeply indented in the middle of one angle. Swampy woods, pond-margins, and wet meadows; N.B. to Minn., s. to N.J., O., and Io.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.