Spikes:

Separate staminate (male) and pistillate (female) spikes, with a single staminate spike up to 3 inches long at the tip of the stem, sometimes with a few pistillate flowers at the tip (gynecandrous) or the base (androgynous) or otherwise mixed. Below the staminate spike are 2 to 6 pistillate spikes, each up to about 2 inches long, thick cylindric, 12 to 18 mm in diameter, short-stalked to nearly stalkless. The uppermost pistillate spikes are typically crowded together just below the terminal spike, are initially erect to spreading and may become drooping; the lowest spike is often longer stalked, some distance from the spike above it, and drooping. At the base of each pistillate spike is a leaf-like bract, those of the lowest spikes significantly over-topping the terminal spike; the lowest bract is up to 30 inches long.

Leaves and stems:

Leaves are basal and alternate, 5 to 16 mm wide, the upper stem leaves over-topping the terminal spike. Stem leaf sheaths are concave to U-shaped at the tip, papery whitish to light brown. The ligule (membrane where the leaf joins the sheath) is longer than wide. Leaves are hairless, W-shaped to flat in cross-section, erect to arching.

Bases are wrapped in a light brown sheath that not fibrous, with old leaves persisting from the previous season. Stems are erect to ascending, 3-sided in cross-section, and mostly smooth except slightly rough on the upper stem. Stems can elongate up to about 3 feet at maturity. Plants form loose to dense clumps from short rhizomes.

Fruit:

Fruit develops in late spring to mid-summer, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Perigynia are widely spreading to angled downward (reflexed, especially near the base of the spike) and tightly packed on the spike. Each pistillate spike contains 100+ fruits.

Pistillate scales are mostly lance-shaped, white to brown tinged, with a green midrib that extends to a long rough-textured awn, and are mostly shorter than the perigynia (including the awn), the scale body well hidden and the awn barely visible except those near the base of the spike. Perigynia are (4.8)6.2 to 8.7 mm long, 1.1 to 1.8 mm wide, green to brownish at maturity, hairless, strongly 14 to 22-veined, stiff, leathery, not much inflated, the body narrowly lance-elliptic, abruptly tapering to a stalk-like base (stipe), gradually tapering to a long beak that has 2 widely spreading teeth 1.2 to 2 mm long at the tip. Achenes are 3-sided, maturing to light brown, oval-elliptic with a persistent style.

Notes:

Carex comosa is a common sedge of swampy or boggy areas, lake and pond shores, and riverbanks in about 2/3 of Minnesota, often in shallow water and rooted in muck.

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 comosa is in the Vesicariae section; some of its common traits are: clump forming or not, rhizomatous, hairless leaves, basal sheaths brown or red-purple, sheaths often splitting into fibers and forming a ladder shape, sheaths with cross partitions between veins (septate-nodulose), 2 to 10 spikes, terminal spike all-staminate, leaf-like bract subtending the lowest pistillate spike, perigynia mostly ascending to spreading, hairless, mostly egg to teardrop shaped, beaked and toothed, at least slightly inflated, achenes 3-sided in cross-section with a persistent style.

Carex comosa is distinguished from all other Minnesota sedges by the combination of: pistillate spikes thick cylindric, erect to spreading to drooping, the uppermost mostly crowded near the staminate spike, perigynia beak with 2 widely spreading teeth 1.2 to 2mm long and a fairly well-defined stipe up to 1mm long. While the spikes of C. comosa resemble those of Carex hystericina, Carex pseudocyperus and Carex lurida, the mature perigynia are more easily distinguished, all having teeth on the beak less than 1mm long that are straight to only slightly spreading. In addition, C. pseudocyperus spikes are more slender, 9 to 12mm in diameter, where C. comosa spikes are 12 to 18mm; C. hystericina has red-purple basal sheaths where C. comosa basal sheaths are light brown; C. lurida (rare in MN) perigynia are larger, 6 to 9 mm long, fewer nerved and more inflated. C. comosa rarely forms sterile hybrids with both C. hystericina and C. pseudocyperus.