Carex muehlenbergii var. enervis
Ill. Carex, 3: 124, plate 400. 1862.
Pistillate scales 2–2.5 × 1.2–1.8 mm. perigynia veinless adaxially, 2.7–3.1 × 1.8–2.3 mm, beak 0.2–0.6(–1.0) mm.
Phenology: Fruiting late spring–early summer.
Habitat: Dry grasslands, open forests, commonly on sand
Elevation: 10–300 m
Ont., Ala., Ark., Conn., Ga., Ill., Ind., Iowa, Kans., Ky., La., Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va.
The distribution and ecology of Carex muehlenbergii var. enervis are unclear due to confusion with var. muehlenbergii. Plants of var. muehlenbergii that have a veinless perigynium have often been misidentified as var. enervis, but those plants are otherwise identical to var. muehlenbergii. Carex muehlenbergii var. muehlenbergii usually occurs on basic to slightly acidic soils; var. enervis often occurs on more acidic soils. It is not clear, however, whether that correlation is consistent.