Spikes:

Separate staminate (male) and pistillate (female) spikes, with 2 to 3 staminate spikes up to 2 inches long at the top of the stem. Below the staminate spikes are 3 to 5 erect to ascending pistillate spikes arising singly from the nodes; often the pistillate spikes have at least a few staminate flowers at the tip (androgynous). Pistillate spikes are short-stalked to stalkless, slender and cylindrical, up to 4 inches long, each with a leaf-like bract at the base of the stalk, the bract of the lowest spike not over-topping the terminal spike.

Leaves and stems:

Leaves are basal and alternate on the lower stem, 3 to 5 leaves per stem, 3 to 6 mm wide; the upper leaves may or may not overtop the flowering stem. Stem leaf sheaths snugly wrap the stem, are translucent whitish to yellowish but reddish-brown along the tip edge, thickened and U-shaped at the tip, firm but often splitting and forming a ladder-shape of thread-like fibers across the front. The ligule (membrane where the leaf joins the sheath) is usually much longer than wide, pointed at the tip with loose tissue around the edge. Leaves are M-shaped in cross-section when young, and hairless though slightly rough along the edges.

Bases are wrapped in a brown to reddish-purple sheath that is strongly ladder-fibrous, and the lowest sheaths lack well-developed blades. Stems are 3-sided, smooth to rough along the angles, erect to ascending to arching, elongating at maturity and may rise above the leaves. Not all plants produce flowering stems. Plants are clump-forming, the old leaves persisting and forming dense hummocks. Large stands are common. 

Fruit:

Fruit develops starting in late spring, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Pistillate spikes are densely packed with 50 to 150 fruits, the perigynia appressed to ascending, and overlapping like shingles.

Pistillate scales are lance-oblong, pointed or blunt at the tip, reddish-brown with a pale midvein, lacking awns, and narrower and usually shorter than the perigynia. Perigynia are green turning light brown at maturity, 1.6 to 3.4 mm long, .8 to 1.8 mm wide, weakly veined on one or both surfaces, hairless, more or less flattened and not inflated but loosely wrapping the achene, lance-elliptic, widest at or below the middle, somewhat rounded at the tip or tapering to a minute, toothless beak. Achenes are 1 to 2 mm long, lens-shaped, brown at maturity.

Notes:

Carex stricta is a common sedge of open, wet places such as meadows, marshes, swampy or boggy shores, and floodplains along streams.

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 stricta is in the Phacocystis section (a combination of former Acutae and Cryptocarpae sections); some of its common traits are: typically clump forming and rhizomatous, leaves V or M-shaped in cross-section when young and hairless except along the edges, spikes long and cylindric, spikes drooping to erect on slender stalks to nearly stalkless, terminal spike usually all staminate or with a few perigynia at the tip, perigynia densely packed, green to brownish, 2-ribbed, weakly veined and short-beaked, achenes lens-shaped with 2 stigmas, growing in wetlands and other wet places.

Carex stricta is among a group of 5 very similar species in Minnesota; the other 4 are Carex aquatilis, C. emoryi, C. haydenii and C. lenticularis. There are a few key characteristics that, in combination, help distinguish them from each other: clump-forming or not, the basal sheaths fibrous or not, the length of the lowest pistillate bract relative to the terminal spike, whether the perigynia is broadest above the middle or not. In some cases, the shape of the ligule, the length of the pistillate scales relative to the perigynia, or other characteristics are also relevant to a correct ID. Most references mention perigynia veins (or lack therof) as an important diagnostic, but we have found these to be pretty obscure in most cases, even under magnification, and sometimes the perigynia base is a bit pleated which might be mistaken for veins.

Of these five species, only C. aquatilis and C. emoryi are colony-forming and not clump-forming. Only C. aquatilis and C. lenticularis have the lowest pistillate bract consistently overtopping the terminal spike. Only C. haydenii and C. stricta have fibrous basal sheaths and form dense hummocks. Only C. aquatilis and C. haydenii should have perigynia widest above the middle, though any of these species may be widest at the middle, at least occasionally. C. aquatilis and C. haydenii have perigynia veinless on both surfaces but veins can be quite faint on the others. Inspect multiple specimens in a population to get a consensus on these traits, and mature specimens are always best though not always available.

C. stricta is distinguished by the combination of: clump-forming, forming dense hummocks, basal sheaths strongly ladder-fibrous, the lowest pistillate bract consistently not overtopping the terminal spike, pistillate spikes up to 4 inches long (though often half that), perigynia more or less flattened, widest at or below the middle and mostly tapered at the tip, and pistillate scales usually shorter than the perigynia. It most closely resembles C. haydenii, which is the only other species of this group that forms dense hummocks, but its basal sheaths are weakly fibrous at best, pistillate spikes tend to be shorter (2 inches or less), pistillate scales are consistently longer than the perigynia, and the perigynia are somewhat smaller, more inflated and rounded at the tip, widest at or above the middle. C. stricta pistillate spikes are much like those of C. aquatilis, which is not clump-forming, lacks the ladder-fibrous basal sheaths, and perigynia are usually widest above the middle.