Cyperus surinamensis |
Cyperus niger |
|
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tropical flatsedge |
black flatsedge, brown cyperus |
|
Habit | Herbs, annual or short-lived perennial, annuals cespitose; rhizomes absent. | Herbs, perennial, rhizomatous. |
Culms | 2–6, trigonous, (10–)35–80 cm × 0.5–2(–4) mm, scabridulous with retrorse prickles (infrequently glabrous or rarely also with extrorse prickles). |
solitary or close together, trigonous, 5–40(–95) cm, glabrous. |
Leaves | 3–9, V-shaped, (12–)25–45(–65) cm × 2–10 mm; blades and bracts without cross ribs. |
(2–)3–7, broadly V-shaped, 3–20(–30) cm × 1.5–3 mm. |
Inflorescences | heads umbellate, 10–20(–30) mm diam.; rays 4–12, 1–6 cm, minutely scabridulous with retrorse prickles; 2d order rays often present, 1–2(–3) cm; 3d order rays rarely present, 0.5–1.5 cm; bracts 3–8, approximately horizontal to ascending at 30°, V-shaped to flat, 2–15(–34) cm × 1–4(–5) mm. |
spikes loosely to densely ovoid to hemispheric, 7–16 mm diam.; rachis 1–2 mm, or absent; rays 1–2, 3–45 mm; if rays absent, inflorescence sessile, dense, 6–20 mm diam; bracts 2–3, horizontal to reflexed downward, broadly V-shaped, 1–15 cm × 1–3 mm. |
Spikelets | (6–)15–40(–65), greenish white, linear to linear-oblong, (3–)4–12(–15) × 1.5–2.5 mm; floral scales 10–50(–65), laterally pale yellow, light brown, or reddish brown, 2-keeled, medially 3-ribbed, lanceolate, 1–1.5 × 0.8–0.9 mm, distinctly reticulate, often scabridulous near apex. |
(3–)5–25(–60), linear to oblong-linear, (3–)5–9 × 1.8–2.3 mm; floral scales 4–18, closely imbricate, chestnut brown, black, or brown, medially green or greenish brown, laterally ribless, medially 2(–3)-ribbed, distinctly 2-keeled basally, ovate to orbiculate, 1.5–2.1 × 1.4–2.2 mm, apex obtuse. |
Flowers | stamen 1; anthers 0.5 mm; styles 0.8–1.1 mm; stigmas 0.5 mm. |
stamens 2; anthers 0.6–0.8 mm, connectives not prolonged; styles 0.4–0.6 mm; stigmas 0.7–2.1 mm. |
Achenes | brown to reddish brown, slightly stipitate, narrowly ellipsoid, 0.7–0.9 × 0.2–0.4 mm, apex apiculate, surfaces papillate or obscurely reticulate to rugulose. |
brown, ellipsoid, 1.2–1.4 × 0.6–0.8 mm, network of ridges forming isodiametric or square cells, slightly stipitate, apex apiculate, surfaces minutely punctate. |
Cyperus surinamensis |
Cyperus niger |
|
Phenology | Fruiting late spring–early fall. | Fruiting summer. |
Habitat | Moist sunny areas with disturbed soils | Swamps, ditches, wet pastures, seeps in montane forests |
Elevation | 0–200 m (0–700 ft) | 0–1200 m (0–3900 ft) |
Distribution |
AL; AR; FL; GA; KS; LA; MS; OK; SC; TN; TX; Mexico; Central America; South America
|
AZ; CA; NM; OK; TX; Mexico; Central America; South America
|
Discussion | Cyperus surinamensis is distinguished readily from all other species of the genus in the New World by the usual presence of retrorse prickles on the culms and rays. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Six varieties (Cyperus niger var. niger, var. castaneus, var. robustus, var. lorentizianus, var. intricate-ramosus, and var. pseudo-elegantulus) were recognized by G. Kükenthal (1935–1936). Based on field observations and measurements of hundreds of collections from Mexico, where the species is most plentiful, it does not seem possible to recognize any of the infraspecific taxa (G. C. Tucker 1983, 1994; G. C. Tucker and R. McVaugh 1993). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 153. | FNA vol. 23. |
Parent taxa | Cyperaceae > Cyperus > subg. Pycnostachys | Cyperaceae > Cyperus > subg. Pycreus |
Sibling taxa | ||
Synonyms | C. diandrus var. castaneus, C. melanostachyus, C. niger var. castaneus | |
Name authority | Rottbøll: Descr. Pl. Rar., 20. (1772) | Ruiz & Pavón: Fl. Peruv. 1: 47. (1798) |
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