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).
Annual herb with red roots, tufted 5 cm - 0.5 m tall
Leaves: basal, alternate, 5 - 25 cm long, 2 - 9 mm wide, flat or inversely W-shaped in cross-section, linear, parallel-veined, keeled beneath, with a sheathing base that encloses the stem.
Inflorescence: consisting of one to three terminal spikes, subtended by spirally arranged leafy bracts. Bracts five to seven, horizontal to ascending, unequal, 10 - 20 cm long, 1 - 3 mm wide, inversely W-shaped in cross-section. Rays (branches of inflorescence) two to six, 1 - 8 cm long. Spikes some stalkless, 1 - 4 cm long, 1 - 1.5 cm wide, densely cylindrical to egg-shaped, consisting of 40 to 80 spikelets.
Flowers: minute, in the axil of a floral scale, lacking sepals and petals. Stamens exserted. Anthers under 0.5 mm long. Pistil one. Style over 0.5 mm long.
Fruit: a one-seeded achene, stalkless, white to light gray to brownish, about 1 mm long and 0.5 mm wide, egg-shaped with a rounded apex bearing a tiny point, unequally three-angled. Seed with a thin, non-adherent wall.
Culm: 5 cm - 0.5 m long, 1 - 2.5 mm wide, triangular to roundly triangular in cross-section, solid.
Spikelets: 3 - 12 mm long, 1 - 1.5 mm wide, linear, four-angled, subtended by two small bracts, with six to sixteen floral scales. Scales appressed, greenish down the middle, light brown and reddish-speckled along the sides, about 1.5 mm long and 1 mm wide, oblong egg-shaped to reverse egg-shaped with a rounded apex bearing a tiny point, four-angled to nearly circular in cross-section, three-ribbed down the middle, lowest one empty.
Similar species: No information at this time.
Flowering: late July to late September
Habitat and ecology: Frequent along shores and ditches, often in alkaline areas.
Occurence in the Chicago region: native
Etymology: Cyperus is the ancient Greek word for sedge. Erythrorhizos means "with red roots."
Author: The Morton Arboretum
Infrequent throughout the state but usually common where it is found. It is generally found on the muddy shores of streams, in dried-up sloughs, and along ditches.
Stout, tufted annual 1-7 dm with red roots; lvs crowded toward the base, with elongate blade 2-9 mm wide; invol bracts several, elongate, unequal; infl of clustered, cylindric spikes, the terminal cluster sessile, the others on rays to 7 cm, each spike 1-4 cm, with numerous serially arranged spikelets on an elongate rachis; spikelets 3-12 נ1-1.5 mm, 6-many-fld; rachilla persistent, with narrow, deciduous, hyaline wings; scales 1.2-1.5 mm, ovate to elliptic, with prominent, green, minutely excurrent keel, 1 or 2 adjacent pairs of much finer lateral nerves, and narrow, golden- brown margins; achenes pearly-white, unequally trigonous, 0.7-1 mm; 2n=96. Streambanks and other wet places; Mass., N.H., and N.Y. to Ont. and N.D., s. to Ark., Tex., and Ariz., and irregularly to the Pacific.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
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