Spikes:

Separate staminate (male) and pistillate (female) spikes, with a single staminate spike up to 1 inch long at the top of the stem, which occasionally has a few to several pistillate flowers at the very tip (gynecandrous) or near the middle. Below the staminate spike are 2 to 6 pistillate spikes. The lowest spike may be widely separated from the spike above it and is typically stalked; the uppermost spikes are stalkless or nearly so and usually more crowded near the tip. At the base of each pistillate spike is a leaf-like bract that is up to 7 inches long, far over-topping the terminal spike. Pistillate spikes are stout, round to elliptic in outline, about ½ inch long, erect to ascending, pale green at flowering time with white, thread-like styles, the staminate flowers with creamy yellow stamens.

Leaves and stems:

Leaves are basal and alternate, mostly near the base, 1.5 to 3.5(4.5) mm wide, shorter or a little longer than the flowering stems. Stem leaf sheaths loosely surround the stem, are translucent and papery on the front side, concave to U-shaped at the tip. The ligule (membrane where the leaf joins the sheath) is poorly developed and obscure. Leaves are hairless though slightly rough along the edges.

Bases are wrapped in a light tan to green sheath that is not fibrous. Stems are slender, 3-sided, mostly erect and mostly smooth. Stems elongate up to 16 inches at maturity and are mostly longer than the leaves. Not all plants produce flowering stems. Plants form loose clumps or mats from short rhizomes.

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. The empty staminate scales persist after fruit has dropped off. Pistillate spikes each contain up to 30 fruits that are tightly crowded on the stalk and mostly widely spreading, occasionally few at the base of the spike are slightly angled down (reflexed).

Pistillate scales are lance to egg-shaped with a blunt or pointed tip, tinged reddish-brown with a green midrib, and about as long as the perigynia body. Perigynia are 1.8 to 3.5 mm long, .9 to 1.5(2) mm wide, hairless, the body turning yellowish at maturity, inflated and loosely wrapping the achene, 5 to 10 nerved (best seen when dry), rather irregular in shape but mostly widest above the middle, tapering to a beak up to half as long as the body, the beak smooth and straight or slightly angled, with 2 minute teeth at the tip. Achenes are 1.1 to 1.8 mm long, up to 1.1 mm wide, 3-sided in cross-section, and mature to brown.

Notes:

Carex viridula is found throughout the northern third of Minnesota, mostly in wet places with sandy, peaty or rocky soil.

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 viridula is in the Ceratocystis section; some of its common traits are: typically clump forming, leaves hairless, leaves V-shaped in cross-section when young, spikes short and stout, terminal spike either all staminate or with a few perigynia, perigynia tightly crowded on the spike, spreading to reflexed, round in cross-section, beaked, the beak usually toothed, 3-sided achenes.

Carex viridula is very similar in appearance to two other Minnesota sedges: Carex cryptolepis and Carex flava. C. viridula is distinguished by perigynia up to 3.5 mm long, perigynia at the base of a spike rarely reflexed, smooth beaks that are about half as long as the body and straight or only slightly angled, pistillate scales tinged dark reddish brown, loose sheaths and obscure ligules. By contrast, C. cryptolepis and C. flava both have perigynia that are larger (to 4.5+ mm long), with longer beaks that are distinctly angled, the perigynia at the base of a spike are typically reflexed, and the ligules well developed. C. viridula has multiple subspecies and vars., all but var. viridula are limited to the east coast, primarily in eastern Canada.