Cyperus seslerioides |
Cyperus rotundus |
|
---|---|---|
Texas flatsedge |
chaguan humatag, coco-grass, nutgrass, pakopako, purple nut-sedge |
|
Habit | Herbs, perennial, cespitose; rhizomes knotty, much branched, 2–5 mm diam., scaly. | Herbs, perennial, stoloniferous; stolons (2–)5–12 cm × 1–2 mm, bearing tubers 3–8(–12) mm diam., wiry, springy when dried, indurate. |
Culms | roundly trigonous, basally with dark fibrous remnants of old leaf sheaths, (0.5–)4–30 cm × 0.4 –1.1 mm, glabrous. |
trigonous, 10–35(–40) cm × 0.7–3.4 mm, basally indurate, glabrous. |
Leaves | 1–5, flat, involute toward apex, 3–18 cm × 1–2.5(–3) mm. |
V-shaped to flanged V-shaped, 5–30 cm × 2–6 mm. |
Inflorescences | heads hemispheric to spheric, (3–)6–15(–24) mm diam.; rays absent; bracts 2–5, horizontal to reflexed, parallel to culm, 1–13 cm × 1–3 mm, margins and keel sparsely minutely scabridulous distally. |
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. |
Spikelets | (5–)20–60(–100), whitish to greenish or brownish, ovoid to oblong-lanceoloid, compressed, 3–7 × 2–4 mm; floral scales (8–)10–12(–24), laterally milky white (infrequently yellowish, pale greenish, brown, or bronze-white), medially green or white, laterally ribless, medially 3-ribbed, ovate to ovate-lanceolate, 1.6–3(–3.4) × 0.8–1.3 mm, apex mucronate to acuminate. |
(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. |
Flowers | stamens 3; anthers linear, (0.4–)0.6–0.8(–1.1) mm, connective not prolonged; styles 0.8–1.8 mm; stigmas (0.5–)1–1.5(–2) mm. |
anthers 1–2.5 mm, styles 1.3–3.5 mm, stigmas (1.8–)2–3.3 mm. |
Achenes | brown to blackish, trigonous, broadly obovoid, 0.5–1 × 0.3–0.75 mm, base slightly stipelike, ± cuneate to rounded, apex apiculate, papillose. |
black, sessile, ellipsoid, abaxial face convex, adaxial face concave, 1.4–1.7(–1.9) × 0.8–1 mm, apex obtuse, surfaces puncticulate. |
Cyperus seslerioides |
Cyperus rotundus |
|
Phenology | Fruiting summer. | Fruiting summer–fall. |
Habitat | Seeps, damp meadows in montane forests | Croplands, disturbed soils usually |
Elevation | 1000–2000 m (3300–6600 ft) | 0–400 m (0–1300 ft) |
Distribution |
AZ; TX; Mexico; South America; Central America (Honduras) |
AL; AR; AZ; CA; FL; GA; LA; MO; MS; NC; NM; SC; TN; TX; VA; Mexico; Central America; South America; Asia; Africa; Australia
|
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. 157. | FNA vol. 23, p. 169. |
Parent taxa | ||
Sibling taxa | ||
Name authority | Kunth: in A. von Humboldt et al., Nov. Gen. Sp. 1: 209. (1816) | Linnaeus: Sp. Pl. 1: 45. (1753) |
Web links |