Cyperus difformis |
Cyperus laevigatus |
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Asian flatsedge, smallflower umbrella sedge, variable flatsedge |
smooth cyperus, smooth flatsedge, smooth nutgrass |
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Habit | Herbs, annual, cespitose. | Herbs, perennial, rhizomatous. |
Culms | 1–15, trigonous, 7–30 cm × 1.2–2.5 mm, soft (flattened in pressing), glabrous. |
single or close together, trigonous to ± terete, (1–)8–30(–60) cm × (0.3–)0.6–1.5(–2.2) mm, glabrous. |
Leaves | 2–7, flat, (2–)7–22 cm × 2.2–4 mm. |
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. |
Inflorescences | heads dense, 7–17 mm diam.; when rays short, heads sessile or nearly so, then densely irregularly lobate, 12–35 mm diam.; rays 1–5, 2–32 mm; bracts 2–4, longest bract erect or nearly so, appearing as continuation of culm, other bracts horizontal to ascending, 1–22 cm × 0.5–3.5 mm, margins and keel minutely scabridulous. |
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. |
Spikelets | 30–120, greenish brown to purplish brown, oblong-ellipsoid, compressed, (2–)3–5(–6) × 0.8–1.2 mm; floral scales (6–)12–20(–30), laterally clear margins, stramineous to deep purple, medially greenish, stramineous, or purplish, laterally ribless, medially 3-ribbed, obovate to orbiculate, 0.6–0.8 × 0.6–0.8 mm, apex mucronulate. |
(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. |
Flowers | stamens 1 or 2; anthers ovoid-ellipsoid, 0.1 mm, connective not prolonged; styles 0.1 mm; stigmas 0.1–0.3 mm. |
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. |
Achenes | light brown, obovoid-ellipsoid, 0.6–0.8 × 0.3–0.4 mm (as long as subtending scale), base cuneate, apex obtuse, apiculate, surfaces finely reticulate, papillose. |
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. |
Cyperus difformis |
Cyperus laevigatus |
|
Phenology | Fruiting summer. | Fruiting summer. |
Habitat | Disturbed, muddy soils, shallow waters | Alkaline grasslands, hotsprings, ditches, brackish marshes |
Elevation | 0–1000 m (0–3300 ft) | 0–1000 m (0–3300 ft) |
Distribution |
AL; AZ; CA; FL; GA; ID; KY; LA; MS; NC; NJ; NM; OR; PA; SC; TN; TX; VA; Mexico; South America; West Indies (Puerto Rico); Central America (Nicaragua, Panama); Eurasia; Indian Ocean Islands; Pacific Islands; Australia [Introduced in North America]
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AZ; CA; NC; TX; Mexico; South America; West Indies; Europe; Asia; Africa
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Discussion | Cyperus difformis is naturalized in the New World and native to the Old World, where it ranges from southern Europe to southern Africa and eastward to Southeast Asia and Australia. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 23, p. 156. | FNA vol. 23, p. 164. |
Parent taxa | Cyperaceae > Cyperus > subg. Pycnostachys | Cyperaceae > Cyperus > subg. Juncellus |
Sibling taxa | ||
Synonyms | C. lateriflorus | Acorellus laevigatus, Chlorocyperus laevigatus, Juncellus laevigatus, Pycreus laevigatus |
Name authority | Linnaeus: Cent. Pl. II, 6. (1756) | Linnaeus: Mant. Pl. 2: 179. (1771) |
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