Culms 5-40 cm. Leaves: blades 3-20(-30) cm × 1.4-3 mm. Inflorescences: proximal bracts with well-developed blades exceeding inflorescence sheaths 2-4(-10) mm; lateral spikes with 4-20 perigynia, approximate or proximal distant, lax, 4-20(-30) × 3-5 mm, middle internodes (0.5-)0.7-1.5 mm; terminal spike usually staminate, occasionally gynecandrous, sessile or short-pedunculate, 3-10(-15) × 0.9-2 mm. Pistillate scales brown with paler or green midvein, divergent in mature fruit, ovate to ovate-circular, 1.2-2.5 × 1.1-1.8 mm, apex subacute to obtuse or cuspidate. Proximal staminate scales brown with paler or green midvein and hyaline margins, oblong-ovate, 2-3.5(-4) mm, apex obtuse to subacute. Perigynia divergent, bright orange, somewhat inflated and fleshy when mature, circular-obovate, 2.3-3.2 × 1.2-1.8 mm, smooth or minutely papillose. Achenes subcircular, 1.4-1.8 × 1-1.5 mm. 2n = 52.
Fruiting summer. Moist, open or shaded habitats, especially meadows and seepage slopes, usually on basic soils; 0-3000 m; Alta., B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Calif., Colo., Conn., Idaho, Ind., Maine, Mass., Mich., Minn., Mont., Nebr., Nev., N.H., N.Mex., N.Y., N.Dak., Ohio, Oreg., R.I., S.Dak., Tex., Utah, Vt., Wash., Wis., Wyo.
The orange perigynia of Carex aurea are unique in North American Carex. The color does not develop until the perigynia are fully mature and ready to be shed, hence most herbarium specimens do not show that feature.
Stems slender, 0.3-4 dm, solitary or in small tufts on long creeping rhizomes; lvs mostly 1-4 mm wide, often surpassing the stems; spikes 2-several, 5-20 mm, approximate or ±remote, erect or loose on slender, sometimes elongate peduncles, the terminal one staminate, less often gynaecandrous, rarely androgynous, the others pistillate, often some of them near-basal; pistillate scales half to fully as long as the perigynia; perigynia ellipsoid to more often obovoid or obovoid-globose, ±rounded and beakless distally, only slightly or not at all compressed, 1.7-3 mm, evidently 12-20-ribbed, varying to nearly nerveless, strongly whitish-papillate on a light green background when young, tending to turn golden or yellow-brown with increasing maturity, becoming somewhat fleshy and obscurely papillate, or sometimes remaining whitish-papillate and not becoming fleshy; stigmas 2 (or 3 in some fls), the achene accordingly lenticular (often plump) or trigonous; 2n=52. Moist or wet places; Nf. to Alas., s. to Pa., n. Ind., Minn., Nebr., N.M. and Calif. (C. garberi and C. hassei, with the perigynia only obscurely nerved and remaining dry and white-papillate at maturity, but the characters confluent)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Frequent on the dunes in Lake County. Its habitat is often that of Carex Garberi, on moist sandy edges of swales and similar situations, but it is also frequently found in richer, mucky soils such as on the border of sloughs and of low wet woods.