393. Carex intumescens Rudge, Trans. Linn. Soc. London, Bot. 7: 97, plate 9, fig. 3. 1804.
Plants cespitose or not, short-rhizomatous. Culms solitary or not, erect, (15–)30–80(–140) cm. Leaves 6–12; basal sheaths purplish red; sheath of distal leaf 0–1(–2.5) cm; ligules rounded, 1–8 mm; blades 8–27 cm × 3.5–8 mm. Inflorescences 2–15 cm; peduncles of proximal pistillate spikes 0.3–1.5 cm, basal 2 peduncles 0.2–2.1 cm apart; of terminal spike 0.5–4 cm; bracts leafy, sheathless, blades 6–21 × 2–6 mm. Spikes: proximal pistillate spikes 1–4, often closely aggregated and difficult to distinguish, 1–12-flowered, ovoid to obovoid, 1–2.7 × 1–2.8 cm; terminal staminate spike 1, 1–5 cm × 1–3 mm. Pistillate scales 1–3-veined, lanceolate-ovate to ovate, 4–9.5 × 2–3.8 mm, apex acute to awned, awns rough, to 6.5 mm. Anthers 3, 2–4 mm. Perigynia ascending to spreading or the basalmost reflexed, strongly 13–23-veined, lanceoloid to ovoid, 10–16.5 × 2.5–6.5 mm, with satiny luster, glabrous; beak poorly defined, 2–4.2 mm. Achenes sessile, ellipsoid to obovoid, flat to convex faces, angles not thickened, 3.5–5.7 × (2.2–)2.5–3.9 mm; style same texture as achene.
Fruiting late spring–early summer. Dry-mesic to wet coniferous, mixed, and deciduous forests, forest openings, thickets, wet meadows, ditches; 0–2000 m; Man., N.B., Nfld. and Labr., N.S., Ont., P.E.I., Que.; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., S.Dak., Tenn., Tex., Vt., Va., W.Va., Wis.
Plants from the south of the species range and from lower elevations northward are usually more robust and have more inflated, ovoid perigynia than northern or high-elevation plants. The latter are sometimes distinguished as Carex intumescens var. fernaldii L. H. Bailey.