Cyperus laevigatus |
Cyperus acuminatus |
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smooth cyperus, smooth flatsedge, smooth nutgrass |
pale umbrella-sedge, sharp-point flatsedge, short flatsedge, short point cyperus, taper-tip cyperus, taper-tip flat sedge |
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Habit | Herbs, perennial, rhizomatous. | Herbs, annual, cespitose. |
Culms | single or close together, trigonous to ± terete, (1–)8–30(–60) cm × (0.3–)0.6–1.5(–2.2) mm, glabrous. |
roundly trigonous, (10–)20–30(–45) cm × 0.4–1.2 mm, distal 1/2 glabrous or infrequently scabridulous. |
Leaves | blades present or reduced to sheaths, base of culm covered with reddish sheath 5–25 mm, distally short toothed 1–2 mm, or leaf blades involute, 1–7 cm × 0.3–1(–1.6) mm. |
2–6(–8), V-shaped or flat, 8–12(–16) cm × 1–2(–4) mm. |
Inflorescences | heads appearing lateral, spikes ± digitate, 5–15 × 5–15 mm; rays absent, sometimes 1, to 2 mm; bracts (1–)2(–3), longer bracts erect, appearing as continuation of culm, shorter bract(s) horizontal or ascending, longer bracts (1–)2–8(–12) cm × 0.5–3 mm, shorter (0.3–)1–4.5 cm × 0.2–1 mm. |
heads hemispheric, 7–12(–15) mm diam.; rays 1–3(–5), 0.5–2 cm; bracts 3–6, longest erect to ascending, flat to V-shaped, (1.5–)3–12(–25) cm × 1–2.5(–3.5) mm. |
Spikelets | (1–)2–7(–14), whitish green to reddish, compressed-turgid, ellipsoid to oblong-lanceoloid, 4–7(–12) × (1.6–)2–3(–3.6) mm; floral scales (8–)12–22, off-white, whitish with red speckles, or with single red spot 0.5 mm wide, medially whitish, oblong-laterally ribless or weakly 2-ribbed, medially weakly 1–3-ribbed, obovate to orbiculate, 1.5–2 × (1.3–)1.6–2 mm. |
(15–)25–50(–75), ovoid, compressed, 4–7 × 2–3 mm; floral scales 8–20(–35), laterally yellowish, yellowish green, or light reddish brown, medially light brown or greenish brown, 2-keeled, subtly 1-ribbed, ovate-lanceolate, 1–2 × 1–1.4 mm, apex acute, mucronate, straight to excurved, glabrous or sparsely scabridulous. |
Flowers | anthers (0.5–)0.7–1 mm, connective apex reddish, 0.1–0.2 mm; styles 0.8–1.2 mm; stigmas 0.7–1 mm. |
stamen 1; anthers 0.5 mm; styles 0.8–1.1 mm; stigmas 0.5 mm. |
Achenes | gray, glossy, oblong-ellipsoid to ovoid, (1.2–)1.3–1.5(–1.8) × (0.7–)0.8–1(–1.2) mm, base cuneate to stipelike, apex apiculate, surfaces finely reticulate to papillate. |
brown, stipitate, broadly ellipsoid, abruptly contracted to base, 0.8–1.1 × 0.3–0.4 mm, stipe 0.1 mm, apex acute, tapering to slender beak formed of persistent style base, surfaces papillose. |
Cyperus laevigatus |
Cyperus acuminatus |
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Phenology | Fruiting summer. | Fruiting summer–fall (Jul–Oct). |
Habitat | Alkaline grasslands, hotsprings, ditches, brackish marshes | Wet, often sandy shores and damp, disturbed soils |
Elevation | 0–1000 m (0–3300 ft) | 0–1500 m (0–4900 ft) |
Distribution |
AZ; CA; NC; TX; Mexico; South America; West Indies; Europe; Asia; Africa
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Mexico (Coahuila, Tamaulipas) [Ala., Ariz., Ark., Calif., Colo., Ill., Ind., Iowa, Kans., Ky., La., Mich., Minn., Mo., Mont., Nebr., N.H., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa. (introduced?), S.Dak., Tenn., Tex., Utah, Va., Wash., Wyo.]
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Discussion | Cyperus laevigatus is one of only two species of subg. Juncellus in the New World. It can be distinguished from all other New World species of Cyperus by its two stigmas and disclike, strongly flattened achene, which is borne with its face toward the rachilla. Species of subg. Pycreus, especially C. niger, have been misidentified as C. laevigatus, probably because of the dark, shiny spikelets. All species of subg. Pycreus have biconvex achenes like C. laevigatus; in species of subg. Pycreus the achene is attached with an edge toward the rachilla; in C. laevigatus the achene faces the rachilla. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Cyperus acuminatus may be introduced in New Hampshire and New York. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 164. | FNA vol. 23, p. 152. |
Parent taxa | Cyperaceae > Cyperus > subg. Juncellus | Cyperaceae > Cyperus > subg. Pycnostachys |
Sibling taxa | ||
Synonyms | Acorellus laevigatus, Chlorocyperus laevigatus, Juncellus laevigatus, Pycreus laevigatus | C. acuminatus var. cyrtolepis, C. cyrtolepis, C. cyrtolepis var. denticarinatus, C. rufescens var. denticarinatus |
Name authority | Linnaeus: Mant. Pl. 2: 179. (1771) | Torrey & Hooker: Ann. Lyceum Nat. Hist. New York 3: 435. (1836) |
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