Herbs, perennial, rhizomatous. Culms trigonous, (10-)20-50 cm × (0.6-)1-2 mm, glabrous or more often scabridulous, either in distal 1/2 or over entire length; basal sheaths, 1-3, light brown, 1-4 cm, papery. Leaves flat to V-shaped, (2-)20-35 cm × 2-6 mm, margins and keel minutely scabridulous; proximal leaves bladeless. Inflorescences: spikes ± umbellate to slenderly (infrequently broadly) ovoid, 10-25 × 7-16 mm; rays 3-5, 1.5-8(-15) cm; bracts 3-7, erect (or declined at most 25-30° from vertical), (2.5-)8-20(-25) cm × (0.5-)1.5-6 mm; rachilla ± deciduous, wingless. Spikelets (1-)5-10(-20), oblong to linear-oblong, quadrangular, 7-10(-18) × (2.8-)3.2-4(-4.5) mm; floral scales deciduous, (1-)5-10(-14), spreading, laterally stramineous or dull whitish, sometimes also red-spotted, medially green, laterally 2-3-ribbed, medially 3-ribbed, broadly ovate to oblong-ovate, (2.3-)2.8-3.2 × (2-)2.4-3.2 mm, apex broadly rounded, often clear-erose, cusp 0.1-0.4 mm in proximal scales, 0.3-1 mm in distal scales. Flowers: anthers 0.8-1.4 mm; styles 0.1-0.3 mm; stigmas 1.5-3 mm. Achenes light to dark brown or nearly black, broadly ellipsoid, infrequently obovoid, 2-2.4 × 0.9-1.4 mm, base cuneate to ± stipelike, apex obtuse to broadly rounded, surfaces papillose. 2n = 166. Fruiting late spring-early summer. Riverbanks, sand bars, lakeshores, sand dunes, sandy openings in woods; 0-1000 m; Alta., Man., Ont., Que., Sask.; Colo., Ill., Iowa, Ky., Mass., Mich., Minn., Mo., Mont., N.J., N.Mex., N.Y., Ohio, Okla., Pa., S.Dak., Tex., Utah, Wash., Wis., Wyo.; Mexico (Coahuila). Cyperus schweinitzii is introduced, but not naturalized, in Massachusetts and Washington.
Perennial herb with short, knotty rhizomes 10 cm - 1 m tall Leaves: alternate, 20 - 35 cm long, 2 - 8 mm wide, flat or V-shaped in cross-section, linear, parallel-veined, keeled beneath, with a sheathing base that encloses the stem. Basal sheaths one to three, light brown, 1 - 4 cm long, papery. Basal leaves bladeless. Inflorescence: consisting of terminal spikes, subtended by spirally arranged leafy bracts. Bracts three to seven, upright, unequal, 8 - 20 cm long, 1.5 - 6 mm wide, much longer than inflorescence. Rays (branches of inflorescence) three to five (some spikes stalkless), 1.5 - 10 cm long. Spikes 1 - 2.5 cm long, 7 - 16 mm wide, reverse conic to oblong, consisting of five to fifteen spikelets. Flowers: minute, in the axil of a floral scale, lacking sepals and petals. Stamens exserted. Anthers to 1.5 mm long. Pistil one. Style under 0.5 mm long. Stigma 1.5 - 3 mm long. Fruit: a one-seeded achene, brown to almost black, 2 - 3 mm long, 1 - 1.5 mm wide, widely ellipsoid with a tapering or more or less stalk-like base and rounded apex, three-angled, bumpy. Seed with a thin, non-adherent wall. Culm: 10 cm - 1 m long, 1 - 2.5 mm wide, triangular in cross-section, solid, often rough above. Spikelets: ascending, 0.5 - 2.5 cm long, 3 - 4.5 mm wide, four-angled, flattened, oblong, subtended by two small bracts, with five to ten floral scales. Scales five to ten, spreading, straw-colored or whitish along the sides, sometimes red-dotted, green down the middle, 2.5 - 3.5 mm long, 2.5 - 3 mm wide, widely egg-shaped to oblong egg-shaped with a broadly rounded apex bearing a tiny point, two- to three-ribbed along the sides, three-ribbed down the middle, lowest one empty.
Similar species: No information at this time.
Flowering: June to late August
Habitat and ecology: Found in disturbed sandy soil, cindery road ballast, and sandy Black Oak savannas.
Occurence in the Chicago region: native
Etymology: Cyperus is the ancient Greek word for sedge. Schweinitzii is named after Lewis David de Schweinitz (1780-1834), the botanist who discovered this species.
Perennial from short, knotty rhizomes; stems 1-10 dm, scabrous above on the sides and sharp angles, 1-2.5 mm thick below the infl; lvs basally disposed, 2-8 mm wide, scabrous on the margins; bracts 3-8, strongly ascending, usually much longer than the infl; sessile spike obconic to oblong; rays 1-8, rarely over 10 cm; spikelets 5-15 in the sessile spike, fewer in the reduced ones, all crowded, ascending, flattened, 5-25 נ3-4.5 mm, 5-18-fld; scales broadly ovate-elliptic to rotund, the body 2.5-3.5 mm, in half-view nearly or fully as wide as long, multinerved, with a conspicuous mucro 0.5-1 mm; rachilla wingless or nearly so; anthers 0.6-1 mm; achenes dark, trigonously oblong with plane or only slightly concave faces, 2-3 mm, half as thick; 2n=ca 166. Sandy soil; Mass. and Que. to Minn., s. and w. to N.J., O., Mo., Utah, N.M., and adj. Mex.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.