Amer. J. Sci. Arts, ser. 2, 4: 24. 1847.
Culms aphyllopodic, smoothly 3-angled, 8–40 cm. Leaves: sheath white-hyaline adaxially, summit U-shaped, smooth; distal ligule 0.5–4.3 mm; blades 0–3 per culm, 12 cm × 1.2–3 mm. Inflorescences green or pale-brown, 1.6–3 cm × 7–15 mm; proximal internode (2–) 4–8 mm, 2d internode 1.7–4 mm; bracts appressed to ascending. Spikes 3–8, densely clustered except, often, the proximal 1–2, obovoid-oblanceoloid, 10–16 × 5–7 mm, base acute to acuminate, apex truncate. Pistillate scales white or gold-hyaline with green or gold midstripe, lanceolate to ovate, to 3.5–4.5 mm, shorter than or longer than perigynia. Perigynia appressed, green or gold to light-brown, conspicuously 3–12-veined abaxially, 0–9-veined adaxially, wing 0.1–0.15 (–0.2) mm wide, narrowly lanceolate, (4.6–) 5.5–7.3 × 0.7–1.2 mm, 0.3–0.4 mm thick; beak tip white, green, or gold, narrowly flat, distance from beak tip to achene 3–5 mm, ± ciliate-serrulate. Achenes elliptic to ovate, 1–1.8 × 0.6–0.8 mm, 0.3–0.4 mm thick. 2n = 64.
Phenology: Fruiting summer–fall.
Habitat: Wet areas, at least seasonally, open, sandy, silty or peaty shores, banks, on limestone
Elevation: less than 1500 m
Alta., B.C., Man., N.W.T., Ont., Que., Sask., Yukon, Alaska, Colo., Iowa, Mich., Minn., Mo., Mont., N.Y., N.Dak., S.Dak., Wash., Wis.
Because Carex sychnocephala often lacks conspicuous rhizomes and has a small diffuse root system, it may appear to be annual. In some situations, it may actually grow as an annual.
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