41. Carex leavenworthii Dewey, Amer. J. Sci. Arts, ser. 2. 2: 246. 1846.
Plants without conspicuous rhizomes. Culms 10–80 cm, 1–2.4 mm wide basally, 0.5–1 mm wide distally. Leaves: sheaths tight, green or, sometimes, green-and-white-mottled, fronts hyaline; ligules to 2 mm, usually longer than wide; widest leaf blades 1.1–3(–4) mm wide. Inflorescences forming dense heads, with 3–8 spikes, 0.7–2 cm × 4.5–9 mm; proximal bracts to 2 cm; spikes with 6–10 ascending or spreading perigynia. Pistillate scales hyaline with green midvein, ovate, 1.5–2.5 × 0.9–1.2 mm, not more than 1/2 length of perigynia, apex acute to cuspidate. Anthers 0.6–1.7 mm. Perigynia pale green, veinless or weakly veined abaxially, 2.5–3.5 × 1.5–2.1 mm, body ovate, widest at 0.25–0.4 length of body, margins smooth or serrulate distally; beak 0.3–0.8 mm, apical teeth 0.1–0.3 mm. Achenes circular, 1–1.5 × 1–1.5 mm.
Fruiting late spring. Dry grasslands, roadsides, open forests, forest edges, lawns; 100–300 m.; Ont.; Ala., Ark., Calif., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Md., Mich., Miss., Mo., Nebr., N.J., N.Y., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Va., W.Va., Wis.
Carex leavenworthii is introduced in California and Wisconsin. Carex leavenworthii is easily confused with C. cephalophora and consequently may be overlooked.