Spikes:

Separate staminate (male) and pistillate (female) spikes. The terminal spike is about 3/8 inch long and typically all staminate, occasionally with a few pistillate flowers at the tip (gynecandrous). Below the terminal spike are 3 to 5 cylindric all-pistillate spikes, each up to about ¾ inch long, the uppermost erect, stalkless or short-stalked, near the terminal spike but not crowding it. Lower pistillate spikes are longer-stalked and erect to ascending or sometimes nodding, the lowest often near the base of the stem. Pistillate spikes each have a leaf-like bract at the base of the stalk, the lower bract(s) usually over-topping the terminal spike.

Leaves and stems:

Leaves are alternate on the lower stem, 1 to 3 mm wide, often over-topping the flowering stem, hairless, V-shaped when young becoming flat, and medium green to bright yellow-green. Stem leaf sheaths are membranous on the front and concave at the tip. Bases are wrapped in a brown sheath that is not fibrous. Stems are slender, 3-sided, rough along the angles on the upper stem, mostly erect to ascending; some may elongate up to 16 inches at maturity. Stems may be single but more typically found in loose to tight clumps.

Fruit:

Fruit develops in late spring through mid-summer, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Pistillate spikes are loosely arranged or somewhat crowded on the stalk, with 4 to 20 fruits, and the perigynia ascending to spreading.

Pistillate scales are slightly spreading away from the perigynia, egg-shaped to nearly round, whitish to brown with a green or pale midrib, pointed at the tip or the midrib extending to a short awn, and half or more as long as the perigynia, rarely the awn extended beyond the perigynia. Perigynia are bright orange at maturity drying to brown, 2.3 to 3.2 mm long, 1.2 to 1.8 mm wide, weakly many-veined, hairless, somewhat inflated and fleshy, egg-shaped to nearly round in outline, round in cross-section, rounded at the base and the tip, beakless but often with a stub of the style persisting at the top. Achenes are 1.4 to 1.8 mm long, plumply lens-shaped, nearly round in outline, and dark brown at maturity.

Notes:

Carex aurea is a common sedge of open or partly shaded areas including wet meadows, fens, ditches, shores, swales, seeps, conifer swamps, bogs and forest openings, in sandy, rocky or calcareous soils. Note that the national distribution map indicates this species is rare in Minnesota, but that is not the case.

Carex is a large genus, with over 600 species in North America and 150+ in Minnesota alone. They are grouped into sections, the species in each group having common traits. Carex aurea is in the Bicolores section; some of its common traits are: clump forming, rhizomatous, basal sheaths not fibrous, leaves V-shaped in cross-section when young, leaves hairless, 2 to 6 spikes, terminal spike all staminate or with pistillate flowers at the tip (gynecandrous), lateral spikes all pistillate and usually stalked, bracts leaf-like, perigynia hairless, generally oval-elliptic, weakly veined, beakless or short-beaked, achenes lens-shaped with 2 stigmas, growing in moist, open areas.

Carex aurea is one of the two members of the Bicolores section in Minnesota, the other being Carex garberi. When mature fruit is present, C. aurea is quite distinctive, since no other sedge has similarly bright orange, nearly round fruit. This coloring is short-lived, however, since it indicates maturity and perigynia will either drop off shortly after or start drying and turn brown. When the perigynia is green, C. aurea may resemble some other Carex species, possibly Carex tetanica or Carex granularis or Carex crawei, all of which have beaked perigynia and 3-sided achenes, and, of course Carex garberi, a very rare sedge which has a terminal spike almost always with several perigynia at the tip, often darker scales that are often more appressed to the perigynia and lack awns, perigynia are usually more tightly crowded in the spike, and are pale green to whitish and densely covered in minute projections (papillose) though magnification is required to see that.