Cyperus giganteus |
Cyperus erythrorhizos |
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giant flatsedge, Mexican papyrus |
red-root cyperus, red-root flat sedge, redroot nutgrass |
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Habit | Herbs, perennial, rhizomatous, stout. | Herbs, annual, cespitose. |
Culms | roundly trigonous, 200–350 cm × 15–50 mm, glabrous. |
trigonous to roundly trigonous, (0.5–)5–25(–105) cm × 1–2.5(–7.5) mm, glabrous. |
Leaves | bladeless. |
flat to inversely W-shaped, 5–25(–90) cm × 2–5(–11) mm. |
Inflorescences | spikes loosely cylindric, 15–40 × 8–16 mm; rays 5–8, ascending to erect, stiff,20–30 cm; 2d order rays 5–15 cm; bracts 10–12, ascending at 30–60°, flat, (8–) 20–45 cm × 4–12 mm; 2d order bracts (5–)15–25 cm × 1.5–5 mm; rachilla persistent, separating laterally, remaining firmly attached basally, wings 0.3–0.4 mm wide. |
spikes 1–3(–6), rather densely cylindric-ovoid, (4–)10–30(–45) × (6–)10–16(–23) mm; rays 2–6(–12), 1–8(–28) cm; bracts (3–)5–7(–11), horizontal to ascending at 30°, inversely W-shaped, (3–)10–20(–70) cm × 1–3(–12) mm; rachilla persistent, at maturity becoming laterally free, remaining firmly attached proximally, wings 0.3(–0.4) mm wide. |
Spikelets | (15–)50–80, slightly compressed, linear, ± quadrangular, 5–12 × 0.6–1.4 mm; floral scales 8–20, appressed, reddish beside 5-ribbed green medial part, white to hyaline near margins, ovate, 1.8–2.2 × 1.2–1.5 mm, apex acute to obtuse. |
(20–)40–80, linear, quadrangular, 3–8(–11) × 1–1.5 mm; floral scales deciduous, 6–16(–30), appressed, laterally light brown with reddish speckles, medially greenish, laterally ribless, medially 3-ribbed, oblong-ovate to obovate, quadrangular to subterete, 1.3–1.5 × 0.8–1.2 mm, apex obtuse, mucronulate. |
Flowers | anthers 0.7–1 mm (connective prolonged beyond anther as red subulate appendage 0.2–0.5 mm, its apex sometimes setose); styles 0.2–0.5 mm; stigmas (0.8–)1.2–1.8 mm. |
anthers 0.2–0.3 mm, connectives 0.1 mm; styles 0.7–0.8 mm; stigmas 0.4 mm. |
Achenes | pale brown, sessile, oblong, 0.9–1 × 0.4–0.5 mm, apex scarcely apiculate, surfaces puncticulate. |
light grayish to brown, sessile, ovoid, (0.4–)0.7–1 × 0.4–0.6 mm, apex rounded, apiculate, surfaces glabrous. |
Cyperus giganteus |
Cyperus erythrorhizos |
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Phenology | Fruiting summer. | Fruiting summer. |
Habitat | Stream banks, marshes | Emergent shorelines |
Elevation | 0–10 m (0–0 ft) | 0–1500 m (0–4900 ft) |
Distribution |
LA; TX; Mexico; Central America; South America; West Indies [Introduced in North America] |
AL; AR; AZ; CA; CT; DC; DE; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; WA; WI; WV; MB; ON; Mexico (Baja California)
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Discussion | Cyperus giganteus was erroneously reported from Florida, a misidentification of C. papyrus (R. R. Haynes and A. Lasseigne 1969). Recently, some nurseries specializing in water plants have begun to offer C. giganteus under the name “Mexican papyrus.” Escaped cultivated plants may be expected in southeastern and southwestern United States. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Source | FNA vol. 23, p. 173. | FNA vol. 23, p. 172. |
Parent taxa | Cyperaceae > Cyperus > subg. Cyperus | Cyperaceae > Cyperus > subg. Cyperus |
Sibling taxa | ||
Synonyms | C. cupreus, C. erythrorhizos var. cupreus, C. occidentalis, C. washingtonensis | |
Name authority | Vahl: Enum. Pl. 2: 364. (1805) | Muhlenberg: Descr. Gram., 20. (1817) |
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