Culms erect or, sometimes, nodding, slender, 15-60 cm. Leaves mid green to yellowish or gray-green, (1-)1.5-2.5 mm wide. Inflorescences erect or, sometimes, nodding, 1.5-5(-7) cm; proximal spikes 0.5-2.5 cm apart; terminal spike ellipsoid to subclavate. Perigynia 2-2.5 × 1-1.5 mm. 2n = 56.

Fruiting May-Jul. Damp, temporarily dry areas, thin-peated mires, thickets, woodlands, heaths, rocky slopes; 0-3500 m; Greenland; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Calif., Colo., Conn., Del., Ga., Idaho, Ind., Maine, Md., Mass., Mich., Minn., Mont., N.H., N.J., N.Y., N.C., Ohio, Oreg., Pa., R.I., Tenn., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.

The mostly northern and western North America, Carex brunnescens subsp. brunnescens grades to subsp. sphaeostachya in the southeastern United States.