Cyperus surinamensis |
Cyperus strigosus |
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tropical flatsedge |
false flatsedge, false nutsedge, straw color cyperus, straw-color flatsedge, straw-colour flatsedge |
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Habit | Herbs, annual or short-lived perennial, annuals cespitose; rhizomes absent. | Herbs, perennial (often flowering first year), 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). |
basally swollen and cormlike, trigonous, (1–)20–40(–90) cm × 1–6 mm, glabrous or few prickles subapically. |
Leaves | 3–9, V-shaped, (12–)25–45(–65) cm × 2–10 mm; blades and bracts without cross ribs. |
flat, (10–)20–40 cm × 1–4(–8) mm, margins and midribs glabrous or scabridulous. |
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 1–4, loosely ovoid to oblong-cylindric; (6–)10–28(–50) × 10–40 mm; rays sometimes absent, usually (1–)3–6(–8), 0.5–7(–25) cm; if absent, inflorescence a congested head; 2d order rays sometimes present, 1–4(–9) cm; rachis 8–18(–25) mm; bracts (3–)5–7(–10), ascending at 30–45°, cross ribs sometimes conspicuous, (1–)10–30(–45) cm × (1–)2–4(–12) mm; rachilla ± deciduous, wings 0.4–0.5 mm wide. |
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. |
(5–)12–50, linear-lanceoloid, compressed, 5–30 × 0.6–0.9 mm; floral scales ± deciduous, 3–11, appressed, medially green, laterally stramineous to pale brown, 3–4-ribbed laterally, (1–)3-ribbed medially, oblong-obovate, 3.2–4.5(–6) × 1–1.8 mm, apex ± acute, overlapping lower 1/4–1/2 of next scale. |
Flowers | stamen 1; anthers 0.5 mm; styles 0.8–1.1 mm; stigmas 0.5 mm. |
anthers 0.3–0.5 mm; styles 1–2 mm; stigmas 3–4 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. |
purplish brown, ± stipitate, narrowly oblong, (1.5–)1.8–2.4 × 0.5–0.6 mm, apex apiculate, acute, surfaces puncticulate. |
Cyperus surinamensis |
Cyperus strigosus |
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Phenology | Fruiting late spring–early fall. | Fruiting summer. |
Habitat | Moist sunny areas with disturbed soils | Pond shores, ditches, damp, disturbed soils, sometimes weeds of gardens or croplands |
Elevation | 0–200 m (0–700 ft) | 0–1500 m (0–4900 ft) |
Distribution |
AL; AR; FL; GA; KS; LA; MS; OK; SC; TN; TX; Mexico; Central America; South America
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AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; NC; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; MB; ON; QC; SK
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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.) |
Cyperus strigosus is usually among the more common Cyperus species throughout its range. Small individuals flowering the first year may be difficult to distinguish from C. polystachyos, C. odoratus, C. erythrorhizos, and C. esculentus, which may be sympatric. Cyperus strigosus has trigonous achenes and three stigmas, unlike C. polystachyos; C. strigosus has flattened spikelets, unlike the subcylindric ones of C. odoratus; C. strigosus has floral scales usually 3 mm or more, unlike the smaller (1.2–1.5 mm) ones of C. erythrorhizos; C. strigosus has deciduous floral scales and a cormlike stem base with stolons, unlike C. esculentus. Cyperus strigosus appears to be closely related to the neotropical C. camphoratus Liebmann; both species have deciduous floral scales and deciduous spikelets (G. C. Tucker 1994). Plants segregated as C. stenolepis cannot be distinguished consistently from C. strigosus on any single charcter, rather they appear to be merely large individuals of C. strigosus with long floral scales and frequently septate inflorescence bracts (M. L. Horvat 1941). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 23, p. 153. | FNA vol. 23, p. 184. |
Parent taxa | Cyperaceae > Cyperus > subg. Pycnostachys | Cyperaceae > Cyperus > subg. Cyperus |
Sibling taxa | ||
Synonyms | C. hansenii, C. stenolepis, C. strigosus var. hansenii, C. strigosus var. stenolepis, Mariscus stenolepis, Mariscus strigosus | |
Name authority | Rottbøll: Descr. Pl. Rar., 20. (1772) | Linnaeus: Sp. Pl. 1: 47. (1753) |
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