Red-rooted flatsedge

Cyperus cupreus J. Presl & C. Presl; C. erythrorhizos var. cupreus (J. Presl & C. Presl) Kükenthal; C. occidentalis Torrey; C. washingtonensis Gandoger

Herbs, annual, cespitose. Culms trigonous to roundly trigonous, (0.5–)5–25(–105) cm × 1–2.5(–7.5) mm, glabrous. Leaves flat to inversely W-shaped, 5–25(–90) cm × 2–5(–11) mm. Inflorescences: spikes 1–3(–6), rather densely cylindric-ovoid, (4–)10–30(–45) × (6–)10–16(–23) mm; rays 2–6(–12), 1–8(–28) cm; bracts (3–)5–7(–11), horizontal to ascending at 30°, inversely W-shaped, (3–)10–20(–70) cm × 1–3(–12) mm; rachilla persistent, at maturity becoming laterally free, remaining firmly attached proximally, wings 0.3(–0.4) mm wide. Spikelets (20–)40–80, linear, quadrangular, 3–8(–11) × 1–1.5 mm; floral scales deciduous, 6–16(–30), appressed, laterally light brown with reddish speckles, medially greenish, laterally ribless, medially 3-ribbed, oblong-ovate to obovate, quadrangular to subterete, 1.3–1.5 × 0.8–1.2 mm, apex obtuse, mucronulate. Flowers: anthers 0.2–0.3 mm, connectives 0.1 mm; styles 0.7–0.8 mm; stigmas 0.4 mm. Achenes light grayish to brown, sessile, ovoid, 0.4–)0.7–1 × 0.4–0.6 mm, apex rounded, apiculate, surfaces glabrous.

Fruiting summer. Emergent shorelines; 0–1500 m; Man., Ont.; Ala., Ariz., Ark., Calif., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Va., Wash., W.Va., Wis.; Mexico (Baja California).