Kongl. Vetensk. Acad. Nya Handl. 24: 145. 1803.
Plants densely cespitose. Culms 50–110 cm; vegetative culms with numerous leaves spaced evenly along distal 1/2. Leaves: sheaths adaxially green-veined nearly to collar, with ± triangular white-hyaline area to 3–8 mm proximal to collar, somewhat loose, expanded near summits, ± wing-angled, adaxially firm, summits U-shaped, somewhat thickened, slightly prolonged beyond collar; distal ligules 4–8(–12) mm; blades 4–10 per fertile culm, 15–40 cm × (2–)3–7 mm. Inflorescences erect, dense distally, brown, 2–5(–8) cm × 10–20 mm; proximal internode 2–20 mm; 2d internode 2–13 mm; proximal bracts bristlelike, 1(–8) cm. Spikes 6–15, overlapping or distinct, ovoid-oblong to globose, 6–12(–16) × 4–8 mm, base rounded to tapered, apex rounded. Pistillate scales white-hyaline or pale silvery brown with green midstripe, lanceolate, (1.9–)2.5–3 mm, 1/2 length of and narrower than perigynia, apex acute to acuminate. Perigynia more than (30–)40 per spike, appressed-ascending to ascending, pale green to pale brown, 3–6-veined abaxially, conspicuously or, occasionally, faintly, 2–4-veined adaxially, often somewhat asymmetric, ovate-lanceolate to ovate-elliptic, plano-convex, 3–5.4 × 1.1–1.7 mm, 0.3–0.5 mm thick, margin flat, including wing 0.1–0.5 mm wide; beak tip flat, ciliate-serrulate, abaxial suture with golden to dark brown hyaline margin, distance from beak tip to achene 1.4–2 mm. Achenes oblong-ovate, 1–1.8 × 0.6–0.9 mm, 0.3–0.5 mm thick. 2n = 70.
N.B., N.S., Ont., Que., Ala., Ark., Conn., D.C., Del., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Mass., Md., Mich., Minn., Miss., Mo., N.C., N.H., N.J., N.Y., Nebr., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Va., Vt., W.Va., Wis., Mexico (Veracruz).
Varieties 2 (2 in the flora).
See note under 146. Carex longii.