Culms usually 10-60 cm. Leaves 0.4-1.55 mm wide, widest (0.65-)0.8-1.6 mm wide. Inflorescences usually 0.8-2 cm; spikes 2-5. Perigynia 1.9-3 × 1.3-2 mm, (1.15-)1.3-1.7(-1.9) times as long as wide; beak 0.45-0.95 mm.

Fruiting late spring-early summer. Bogs, acidic coniferous swamps, wet, acidic soils; 0-300 m; N.S., Ont., Que.; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Ky., La., Maine, Md., Mass., Mich., Miss., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Tex., Vt., Va.

The two Carex atlantica subspecies are quite distinct over most of their ranges, but in the south, especially in the Gulf States, intermediates and specimens showing some characteristics of one subspecies and some of the other are occasional.

Known in Indiana from a single collection by M. W. Lyon, Jr.: moist woods on dunes at Mineral Springs, Porter County, June 17, 1923.