Spikes:

Separate staminate (male) and pistillate (female) spikes, with a single staminate spike up to 1 inch long at the tip of the stem. Below the staminate spike are 1 or 2 pistillate spikes, ¼ to 1 inch long, on slender, erect stalks and well separated from each other. At the base of each pistillate stalk is an erect, leaf-like bract that may or may not overtop the associated spike. Bract sheaths are long and loosely wrap the stem.

Leaves and stems:

Leaves are alternate, flat, 1 to 3(-4) mm wide. Leaves of flowering stems are all near the base, erect to ascending and quite short. The blades of non-flowering stems are up to 10 inches long, mostly arching, and may appear to over-top the flowering stems. Leaf sheaths are straight across to concave at the tip, those near the base strongly red-purple and tightly wrapping the stem, becoming more loosely wrapping and whiter above. The ligule (membrane where the leaf joins the sheath) is about as wide as or wider than long.

Bases are wrapped in a strongly red-tinged sheath that is not fibrous and is bladeless or nearly so. Stems are single, slender, erect to spreading, 3-sided, mostly smooth, and may elongate up to about 18 inches at maturity. Plants form loose to dense clumps and often form loose non-flowering colonies from long, shallow rhizomes.

Fruit:

Fruit develops in mid to late spring, the pistillate spikes forming clusters of seeds (achenes), each wrapped in a casing (perigynium), subtended by a scale. Pistillate spikes each contain 6 to 15 fruits that are erect to ascending, usually loosely arranged on opposite sides of the stalk (2-ranked), less often more tightly packed and overlapping.

Pistillate scales are oval to egg-shaped, blunt to pointed at the tip, translucent white to light brown to purplish-brown with a green midrib that sometimes extends to an awn, the scale body about as wide as the perigynia and half to nearly as long, the awn sometimes exceeding the perigynia. Perigynia are 2.5 to 4 mm long, 1 to 2 mm wide, green to brown at maturity, about 20-veined (best seen when dry), hairless, slightly inflated especially towards the base, 3-sided in cross-section, the body usually widest above the middle, with a minute, strongly bent, toothless beak at the tip. Achenes are 2 to 2.5 mm long, 3-sided in cross-section, yellowish-brown at maturity.

Notes:

Carex woodii is sedge of rich, deciduous woods and reaches the western edge of its range in Minnesota. The earliest records are from the 1980s in southeast Minnesota. According to the DNR, at the time it was considered rare and was listed as a Special Concern species in 1984, but subsequent biological surveys across the state discovered over 90 additional populations, most in central Minnesota, so it was delisted in 2013.

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 woodii is in the Paniceae section; some of its common traits are: clump forming or not, rhizomatous, hairless leaves, basal sheaths brown or red-purple, sheaths sometimes fibrous, 2 to 4 spikes, terminal spike all-staminate, lateral spikes all-pistillate and stalked, leaf-like bract subtending the lowest pistillate spike with a sheath more than 4 mm long, perigynia ascending to spreading, hairless, weakly 3-sided to round in cross-section, beaked or not, at least slightly inflated, achenes 3-sided in cross-section.

Carex woodii is distinguished from all other Minnesota sedges by the combination of: loosely to densely clump-forming, rhizomatous with large, loose, non-flowering colonies common; sheaths strongly red-purple especially at the base; stem leaves on flowering stems few, very short and near the base; a single terminal staminate spike; usually 1 or 2 erect, stalked pistillate spikes each containing 6 to 15 fruits alternately and (usually) loosely arranged on the stalk; perigynia up to 4 mm long, widest near the tip, with a minute bent beak; achenes 3-sided. Vegetative stands may resemble some other sedges, notably Carex pensylvanica or Carex tetanica, but the lower sheaths of C. woodii should be distinctive.