Cyperus rotundus |
Cyperus cuspidatus |
|
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chaguan humatag, coco-grass, nutgrass, pakopako, purple nut-sedge |
coastal plain flatsedge |
|
Habit | Herbs, perennial, stoloniferous; stolons (2–)5–12 cm × 1–2 mm, bearing tubers 3–8(–12) mm diam., wiry, springy when dried, indurate. | Herbs, annual, cespitose. |
Culms | trigonous, 10–35(–40) cm × 0.7–3.4 mm, basally indurate, glabrous. |
1–6(–25), trigonous to roundly trigonous, (0.5–)2–5(–9) cm × 0.2–0.4–(0.6) mm, glabrous. |
Leaves | V-shaped to flanged V-shaped, 5–30 cm × 2–6 mm. |
1–6, V-shaped, 1–6 cm × 0.3–1 mm. |
Inflorescences | spikes 1(–3), broadly ellipsoid, (12–)15–25(–30) × (12–)20–30(–50) mm, rays (3–)4–6(–7), 0.2–10 cm;, bracts (2–)3–5, horizontal to ascending at 45°, V-shaped to flanged V-shaped, 0.5–10 cm × 0.5–4 mm, rachilla persistent, wings 0.5–1 mm wide. |
heads digitate, loosely ovoid, 3–18 × 3–26 mm; rays (0–)1–6(–8), 2.5–20(–30) mm; bracts 2–3(–5), horizontal to ascending at 45(–60)°, V-shaped, 2–60 × 0.3–1.2 mm. |
Spikelets | (2–)3–7(–12), compressed, linear, 4–40 × 1.3–1.8 mm, floral scales persistent, 6–36(–42), spreading or appressed, purple to reddish brown, with narrow clear border and green midrib, 7–9-ribbed, ovate, (1.8–)2.6–3.4 × 2.2–3 mm, apex obtuse. |
(3–)10–20(–30), greenish to reddish brown, narrowly ellipsoid to oblong, 3–11 × (0.8–)1.2–1.5 mm; floral scales (3–)6–20(–28), laterally greenish to reddish brown, glossy, medially greenish to light reddish brown, strongly recurved, laterally ribless, medially strongly 3-ribbed, oblong-ovate, (0.8–)1–1.3 × 0.8–1(–1.2) mm, apex emarginate, cusp 0.6–1.2 mm. |
Flowers | anthers 1–2.5 mm, styles 1.3–3.5 mm, stigmas (1.8–)2–3.3 mm. |
stamens 2 or 3; anthers oblong-ovoid, 0.1(–0.2) mm; styles (0.2–)0.4–0.6 mm; stigmas 0.3–0.5 mm. |
Achenes | black, sessile, ellipsoid, abaxial face convex, adaxial face concave, 1.4–1.7(–1.9) × 0.8–1 mm, apex obtuse, surfaces puncticulate. |
brown, oblong-obovoid, (0.5–)0.6 × (0.3–)0.4 mm, base cuneate, apex blunt, surfaces coarsely papillose. |
Cyperus rotundus |
Cyperus cuspidatus |
|
Phenology | Fruiting summer–fall. | Fruiting summer. |
Habitat | Croplands, disturbed soils usually | Damp, disturbed soils |
Elevation | 0–400 m (0–1300 ft) | 0–300 m (0–1000 ft) |
Distribution |
AL; AR; AZ; CA; FL; GA; LA; MO; MS; NC; NM; SC; TN; TX; VA; Mexico; Central America; South America; Asia; Africa; Australia
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AL; FL; GA; SC; Mexico; Central America; South America
|
Discussion | Cyperus rotundus is documented in Connecticut, Delaware, New York, and Pennsylvania; there is no evidence of persistent populations. Cyperus esculentus and C. rotundus are the only two species of subg. Cyperus in the New World that produce tuberiferous stolons. The two species also have persistent floral scales and persistent rachillas, a combination of characteristics not found in any other New World species of Cyperus. Cyperus rotundus is distinguished from other species of the genus in the New World by its open spikes composed of linear reddish spikelets borne on a conspicuous slender rachis. Cyperus rotundus is usually acknowledged to be the world’s worst weed (cf. G. C. Tucker 1987). In the United States, it does not grow north of the mean 1°C January isotherm. Cyperus esculentus (preceding species) is a serious weed in much of the world, especially in cooler regions where the more tropical C. rotundus does not grow. Cyperus esculentus is able to tolerate lower air temperatures (as low as -18°C). The two species apparently differ also in their thermal optima for growth. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
|
Source | FNA vol. 23, p. 169. | FNA vol. 23, p. 158. |
Parent taxa | Cyperaceae > Cyperus > subg. Cyperus | Cyperaceae > Cyperus > subg. Pycnostachys |
Sibling taxa | ||
Name authority | Linnaeus: Sp. Pl. 1: 45. (1753) | Kunth: in A. von Humboldt et al., Nov. Gen. Sp. 1: 204. (1816) |
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