Flower:

Separate staminate (male) and pistillate (female) spikes, with a single staminate spike ½ to 1+ inches long at the top of the stem. Below the staminate spike are 2 to 5 slender-stalked, all-pistillate spikes, widely spaced and arising singly from the nodes with a leaf-like bract at the base of the stalk. The stalk of the lowest spike is longest with the stalks becoming progressively shorter as they ascend the stem, the stalks erect to ascending, sometimes drooping. Pistillate spikes are slender, few-flowered, up to about 3 inches long, with long, curly, white, thread-like styles.

Leaves and stems:

Leaves are basal and alternate, mostly near the base, 1 to 3 mm wide, as long as or shorter than the flowering stems, flat and arching at maturity. Stem leaf sheaths loosely wrap the stem and are translucent whitish. The ligule (membrane where the leaf joins the sheath) is about as long as or shorter than wide. Leaves are M-shaped in cross-section when young, and hairless though slightly rough on both surfaces.

Bases are wrapped in a purple-tinged to deep maroon sheath that is not fibrous. Stems are slender, 3-sided and mostly smooth. Flowering stems become leaning to arching, elongating as much as 30 inches at maturity and usually longer than the leaves at maturity. Plants are clump-forming and not all plants produce flowering stems, but both vegetative and flowering plants produce horizontal stems (stolons) that can extend up to 6 feet, have widely spaced, reflexed leaves, and root at the tips forming new shoots.

Fruit:

Fruit develops in late spring through early 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 10 or fewer fruits that are loosely arranged on the stalk, spaced 3 to 15 mm apart.

Pistillate scales are lance-oblong, translucent white sometimes tinged chestnut brown, with a green midrib that turns brown, blunt to pointed at the tip or the midrib extending to a rough awn up to 3 mm long, and are shorter than the perigynia, though the awn may extend beyond the perigynia. Perigynia are green turning yellowish at maturity, 5 to 6.5 mm long, .8 to 1.8 mm wide, 2-ribbed, short-hairy except near the base, snugly wrapping the achene, the body narrowly lance-elliptic, tapering to a long, slender beak with 2 minute teeth at the tip. Achenes are 1.8 to 2.5 mm long, up to 1 mm wide, 3-sided in cross-section, and mature to golden brown.

Notes:

Carex assiniboinensis is found throughout Minnesota in dry to mesic to moist hardwood forest and floodplains. The first record of it in the Bell Herbarium was from a floodplain forest in Itasca County in 1978.

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 assiniboinensis is in the Hymenochlaenae section; some of its common traits are: typically clump forming and forming loose colonies, leaves M-shaped in cross-section when young, spikes long and cylindric and drooping on slender stalks, terminal spike either all staminate or with a few perigynia (usually at the tip, occasionally the base), perigynia round in cross-section, 2-veined, beaked, the beak usually toothed, 3-sided achenes, often growing in woodlands.

Carex assiniboinensis is not likely to be confused with other sedges: the few-flowered spikes of long, slender, hairy perigynia that are yellowish when mature, combined with the long, tip-rooting stolons are unique to this species. The stolons are recognizable even in vegetative populations; they are initially erect like a flowering stem, but have alternate leaves that appear to be pointing down (reflexed) rather than up. The stolons eventually become spreading and run along the ground. One plant in our garden had dozens of stolons radiating in all directions. Left to its own devices, it would likely overtake the yard. In the wild, it can create sizable colonies.