Spikes:

A cluster up to 2 inches long at the top of the stem, made up of 5 to 10 spikes, oval-elliptic in outline, the uppermost spikes overlapping and more crowded than the lower. All spikes have a few staminate (male) flowers at the tip and pistillate (female) flowers at the base (androgynous).

At the base of lower spikes is a scale-like bract with a bristle-like tip that may be longer than the spike but does not typically overtop the terminal spike. Bracts become smaller as they ascend the stem, are absent from the upper spikes and can drop off the lower spikes as they mature.

Leaves and stems:

Leaves are alternate with 3 or 4 leaves on the lower fourth of the stem, 1.5 to 2.5 mm wide, shorter than the flowering stem, flat, hairless, rough along the edges especially near the tip. Stem leaf sheaths tightly wrap the stem, are thin and fragile, light green to whitish. The ligule (membrane where the leaf joins the sheath) is about as wide as or wider than long. Bases are brownish and not fibrous. Stems are hairless, erect to asending, 3-sided in cross-section, mostly smooth except just below the spikes. Stems can elongate to as much as 30 inches at maturity and are longer than the leaves. Plants are loosely clump forming.

Fruit:

Fruit develops in late spring to early summer, the spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Perigynia are mostly erect, overlapping and crowded on the spike. Each spike contains 3 to 10 fruits.

Pistillate scales are lance to egg-shaped, thin, brown with a green midrib drying to light brown, the tip extending to a short awn, are slightly longer and wider than the perigynia and can drop off as fruit matures. Perigynia are 2.6 to 3.6 mm long, 1.1 to 1.5 mm wide, pale green to pale brown with a translucent body at maturity, hairless, veinless or obscurely veined on both sides, flattened on the back, the body oval, tightly wrapping the achene, tapering to a spongy stalk-like base, tapering at the tip to a toothed beak that is finely serrated along the edges. Achenes are lens-shaped, reddish-brown, about 1.5 mm long, nearly as wide, egg-shaped to nearly round, and are visible through the translucent perigynia.

Notes:

Carex hookerana, spelled C. hookeriana in several references, is sedge of the northern Great Plains, more common in Canada, the southern edge of its range just dipping into North Dakota and Minnesota. According to the DNR, it was unknown here until 2005, when it was discovered along a lightly used, grassy field road through a narrow strip of dry oak woodland in Becker County, then another small population was found in a Wildlife Management Area in Marshall County. Due to the limited number of sites, small sizes of the populations, and lack of info about its total distribution and habitat needs, it was listed as a Special Concern species in 2013. A third small population was recently found in Roseau County, also in a grassy opening of a wooded area. In Fillmore County, a couple plants were discovered in a horse pasture in 2014 and determined to be likely introduced there; it is unknown if they persisted.

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 hookerana is in the Phaestoglochin section; some of its common traits are: clump forming, basal sheaths usually fibrous, sheath fronts cross-wrinkled (rugose), leaves hairless and V-shaped in cross-section when young, 3 to 15 stalkless spikes (rarely the lower are branched), terminal spike with staminate flowers at the tip (androgynous), lateral spikes androgynous or all pistillate, perigynia ascending to spreading and flattened on the back side, rounded and spongy at the base, beaked, the beak usually toothed, flattened lens-shaped achenes.

Carex hookerana is distinguished by its 5 to 10 spikes at the tip of the stem, the lower spikes more widely spaced than the upper, up to 10 perigynia per spike, perigynia nearly transparent at maturity, pistillate scales slightly longer and wider than the perigynia, tight sheaths that are thin and easily torn. Where we photographed it, it was mixed with Carex siccata, which at a casual glance may have a similar arrangement of spikes, but has larger perigynia (3.9 to 6.5 mm long), a thicker sheath that does not tear so easily, and is not clump-forming but tends to form colonies in lines from scaly rhizomes.