90. Carex interior L. H. Bailey, Bull. Torrey Bot. Club. 20: 426. 1893.
Carex scirpoides Schkuhr ex Willdenow, Sp. Pl. 4(1): 237. 1805, not C. scirpoidea Michaux 1803
Culms 10–95 cm. Leaves 3–5 per culm; sheaths tight, inner band hyaline, 1.8–13 cm, apex concave, glabrous; ligule of distalmost leaf obtuse to rounded, 0.6–2.2 mm; blades plicate, 6–31 cm × 0.6–2.4(–2.7) mm, widest leaf 1–2.4(–2.7) mm wide. Inflorescences 0.8–3.7 cm; spikes 2–5(–7); lateral spikes pistillate often with few staminate flowers proximally, 3–9.5 mm, sessile, staminate portion 3-flowered, to 2.2 mm, pistillate portion 3–18-flowered, 2.3–8 mm; basal 2 spikes 2.1–11 mm apart; terminal spike 5.2–20 mm, gynecandrous, staminate portion 3–10-flowered, 2.2–14.5 × 0.7–1.4 mm, pistillate portion 4–16-flowered, 3–7 × 4–5.8 mm. Pistillate scales ovate, 1.2–2.1(–2.4) × 1–1.6 mm, apex obtuse. Staminate scales ovate, 1.4–2.9 × 1–1.3 mm, base clavate, apex obtuse to acute. Anthers 0.6–1.4 mm. Perigynia spreading to reflexed, castaneous to dark brown, 4–12-veined abaxially, sometimes faintly, 0(–6)-veined adaxially over achene, ovate, often convexly tapered from widest point to beak, forming a “shoulder,” 1.95–3(–3.3) × 1.1–1.8 mm, 1.4–2(–2.2) times as long as wide; beak 0.4–0.95 mm, 0.18–0.44 length of body, setulose-serrulate, teeth 0.15–0.4 mm. Achenes ovate, 1.2–1.8 × 0.95–1.5 mm.
Fruiting late spring–early summer. Wet meadows, wet prairies, fens, coniferous and deciduous swamps, river and lakeshores, seeps; usually in ± calcareous, open sites; 0–2700 m; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Ariz., Ark., Calif., Colo., Conn., Idaho, Ill., Ind., Iowa, Kans., Maine, Mass., Mich., Minn., Mo., Mont., Nebr., Nev., N.H., N.J., N.Y., N.Dak., Ohio, Oreg., Pa., S.Dak., Utah, Vt., Va., W.Va., Wash., Wis., Wyo.; Mexico (Chihuahua).
When Carex interior occurs with C. sterilis, C. echinata, and (rarely) C. atlantica, usually sterile intermediates, presumably hybrids, may occasionally be found.