Spikes:

Separate staminate (male) and pistillate (female) spikes, with a single staminate spike up to 2 inches long at the tip of the stem, sometimes with a few pistillate flowers at the tip (gynecandrous) or the base (androgynous). Below the staminate spike are 1 to 4 pistillate spikes, each up to about 2½ inches long, thick cylindric, short-stalked. The uppermost pistillate spikes are typically close together (but not crowded) 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 over-topping the terminal spike; the lowest bract is up to 12 inches long.

Leaves and stems:

Leaves are basal and alternate, 2.5 to 8.5 mm wide, at least some 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 as long as or longer than wide. Leaves are hairless, W-shaped to flat in cross-section, erect to arching.

Basal sheaths may become fibrous and are usually strongly tinged red to purple, 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 40 to 100+ fruits.

Pistillate scales are lance-oblong, initially white turning brown to red-brown, with a green midrib that extends to a long rough-textured awn, and are shorter than the perigynia (including the awn), the scale body mostly well hidden with some awns partly visible. 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 13 to 21-veined, inflated, the body elliptic, widest near the middle, tapering to a long beak that has 2 straight teeth less than 1 mm long at the tip. Achenes are 3-sided, maturing to brown, oval-elliptic with a persistent style.

Notes:

Carex hystericina is a common sedge of wet areas and found throughout Minnesota, mostly on lake and pond shores, wet meadows, wet ditches, marshes, and the edges of bogs and swamps, mostly in calcareous soils.

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 hystericina 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 hystericina is distinguished from all other Minnesota sedges by the combination of: red-purple at the base, pistillate spikes thick cylindric, erect to spreading to drooping, the upper near the terminal spike but not especially crowded, perigynia essentially stalkless, inflated with 13 to 21 veins, a long beak with 2 erect teeth less than 1mm long. The spikes of C. hystericina resemble those of Carex comosa and Carex pseudocyperus , both of which have brown basal sheaths and stiff, leathery perigynia with a stalk-like base (stipe), where C. hystericina has red-purple bases and thinner walled perigynia that are stalkless or nearly so. In addition, C. comosa has longer, widely spreading teeth on the perigynia beak and C. pseudocyperus has a less-well defined, stouter beak than C. hystericina. Also similar is the very rare Carex lurida, which has perigynia with 10 or fewer veins, proportionately wider (to 4mm) and a proportionately longer beak with teeth .5mm long or less. C. hystericina has been known to hybridize with several other members of the Vesicariae section.