Cyperus rotundus |
Cyperus fuscus |
|
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chaguan humatag, coco-grass, nutgrass, pakopako, purple nut-sedge |
brown flatsedge, brown galingale |
|
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. |
trigonous, 2–30 cm × 0.6–1.1 mm, glabrous. |
Leaves | V-shaped to flanged V-shaped, 5–30 cm × 2–6 mm. |
flat, 4–10 cm × 2–4 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. |
rays 1–3, 0.2–1.5 cm; 2d order rays present in robust plants, to 5 mm; bracts 2–3, longest erect, others spreading, 1–20 cm × 1.5–3 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. |
3–12, narrowly ellipsoid, flattened, 3–7 × 0.9–1.2 mm; floral scales 8–12(–16), laterally purplish brown, medially greenish yellow, 3-ribbed medially, orbiculate, 0.9–1.1 × 1 mm, apex mucronate. |
Flowers | anthers 1–2.5 mm, styles 1.3–3.5 mm, stigmas (1.8–)2–3.3 mm. |
stamen 1; anthers ellipsoid, 0.2 mm, connective not prolonged; styles 0.3–0.4 mm; stigmas 0.3 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. |
light brown, ellipsoid, 0.7–0.9 × 0.4 mm, base barely stipelike to narrowly cuneate, apex acute, surfaces glabrous. |
Cyperus rotundus |
Cyperus fuscus |
|
Phenology | Fruiting summer–fall. | Fruiting summer. |
Habitat | Croplands, disturbed soils usually | Damp, disturbed soils, emergent shorelines, puddles |
Elevation | 0–400 m (0–1300 ft) | 0–1700 m (0–5600 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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CA; CT; MA; MD; MO; NE; NJ; NV; PA; SD; VA; ON; QC; Eurasia [Introduced in North America]
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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.) |
A native of temperate Eurasia, Cyperus fuscus is intermittently adventive and locally established 35°–45° N latitude. The report from New York (M. L. Fernald 1950) is based on a misidentification of C. diandrus (R. S. Mitchell and G. C. Tucker 1997). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 169. | FNA vol. 23, p. 157. |
Parent taxa | Cyperaceae > Cyperus > subg. Cyperus | Cyperaceae > Cyperus > subg. Pycnostachys |
Sibling taxa | ||
Name authority | Linnaeus: Sp. Pl. 1: 45. (1753) | Linnaeus: Sp. Pl. 1: 46. (1753) |
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