Plants densely cespitose, in small clumps; rhizomes short. Culms erect to arching, slender, 15-90 cm. Leaves: sheaths relatively tight, pale to mid brown abaxially, inner band thin and hyaline, often concave at summit; ligules as long as wide; blades green to yellowish green, flat, 10-25(-40) cm × 0.5-2 mm, shorter than culms. Inflorescences erect to somewhat nodding, 1.5-7 cm × 3-6 mm; proximal bracts bristlelike-prolonged, shorter than to exceeding spikes; distal bracts usually scalelike. Spikes 5-10, gynecandrous, proximal ± separate, distal closely approximate, containing 5-10 perigynia, sessile, globose to short-oblong, 3-7 × 3-4 mm; terminal spike staminate for less than 1/2 of length, scarcely clavate. Pistillate scales white-hyaline with green, 3-veined center, often brown tinged, ovate, subequal to, not concealing perigynia, apex obtuse to acute. Perigynia appressed-ascending to loosely spreading at maturity, green or brown, often dark brown in age, lightly several-veined, elliptic-ovate, 2-2.5 × 0.8-1.5 mm, widest near middle, membranous; beak short, margin serrulate. Achenes pale to mid brown, ovate-orbiculate, 1.25-1.5 × 0.8-1 mm, glossy. 2n = 56. Carex brunnescens is variable across its wide distribution; it deserves a monographic treatment. Many taxa have been described. Most variation is presumably of ecophenotypic nature; when growing in shady habitats the species is slender and weak and the scales are not or but little colored; in more exposed sites it is stiffer, and the scales become strongly brownish tinged. Only two subspecies are recognized here. Subspecies alaskana and subsp. pacifica (see A. Kalela 1965) seem to grade to the typical subsp. brunnescens. A short-leaved plant with short and red tinged perigynia from western United States (Colorado, Montana, Utah, Wyoming) may represent a southern subspecies and should be studied in greater detail.
Much like no. 48 [Carex canescens L.]; lvs green, 1-2.5 mm wide; spikes avg smaller, 4-8 mm, brownish, or sometimes pale as in no. 48; perigynia mostly 5-10(-15), a little more spreading, so that the beak-apiculations interrupt the outline of the spike, evidently but rather finely several-nerved dorsally, nerveless or obscurely nerved ventrally, smoother-textured, the wall very thin distally and easily ruptured; dorsal suture well developed, 0.4-0.8 mm, extending onto the distal end of the body, often with a narrow, white-hyaline, overlapping longitudinal flap; 2n=56. Bogs and wet woods; circumboreal, s. to N.J., O., Mich., Minn., and in the mts. to N.C.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.