Spikes:

Separate staminate (male) and pistillate (female) spikes, with a single staminate spike about 1 inch long at the tip of the stem. Below the staminate spike are 2 to 4 slender-stalked pistillate spikes, usually all near the tip but not crowded, arising singly from the nodes with a leaf-like bract at the base of the stalk, the bract of the uppermost spike(s) reduced to a scale. The stalk of the lowest spike is longest with the stalks becoming progressively shorter as they ascend the stem, the stalks initially erect to ascending, becoming drooping with maturity. Pistillate spikes are cylindrical, up to about 1 inch long, green at flowering time with white, thread-like styles, and the staminate spike with creamy yellow stamens.

Leaves and stems:

Leaves are basal and alternate, mostly near the base, 2.5 to 9 mm wide, shorter than the flowering stems, becoming arching. Stem leaf sheaths loosely wrap the stem, are translucent whitish and densely covered in short hairs. The ligule (membrane where the leaf joins the sheath) is longer than wide. Leaves are M-shaped in cross-section when young, sparsely hairy on the upper surface and edges and more densely hairy on the underside.

Bases are wrapped in a sheath that is hairy, not fibrous, and is typically tinged red to purple, turning brown as it withers with age. Stems are slender, 3-sided and sparsely hairy. Stems become leaning to nearly prostrate, about as long as the leaves at flowering time but elongating up to 3 feet maturity, much longer than the leaves. Plants form loose clumps and can create loose colonies from short rhizomes.

Fruit:

Fruit develops in late spring through mid-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 to 40 fruits, spaced about 1 mm apart on the stalk.

Pistillate scales are egg-shaped, translucent white to chestnut brown with a broad green midrib, pointed at the tip or the midrib extending to an awn less than 1 mm long, often hairy around the tip edge, and nearly as long as the perigynia or shorter. Perigynia are green often dotted red, 2.5 to 5 mm long, 1.3 to 2.5 mm wide, 2-ribbed with 5 to 7 faint veins, hairless, loosely wrapping the achene, oval-elliptic tapering to a beak about half as long as the body, with 2 minute teeth at the tip. Achenes are 1.5 to 2 mm long, up to 1.5 mm wide, 3-sided in cross-section, and mature to dark brown.

Notes:

Minnesota being at the southwest edge of its range, Carex castanea is found in our northern forests, cedar-spruce bogs and swamps, sedge meadows, and on the rocky shore of Lake Superior.

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 castanea 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 castanea is distinguished from other sedges in Minnesota by the combination of: hairy leaves and stems, terminal spike all staminate, pistillate scales usually with a few hairs around the edge, oval-elliptic perigynia with a long beak. It most closely resembles C. sprengelii, which is completely hairless and has more spherical perigynia with a more abrupt taper to the beak. While both C. formosa and C. davisii are also hairy with dangling pistillate spikes, their perigynia has a rather shorter beak, C. formosa pistillate spikes have 1 or 2 staminate flowers or empty scales at the base, and C. davisii scales are long-awned and often longer than the perigynia. C. castanea has been known to hybridize with other members of its section, C. arctata in particular, though these hybrids are not well documented in Minnesota.