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Genus Cyperus Family Cyperaceae

Description: Annual or perennial herbs, tufted or rhizomatous, rarely tuber-bearing. Culms triquetrous to terete, nodeless.

Leaves sometimes reduced to sheaths; ligule present or absent.

Inflorescence simple or compound, umbel-like or head-like, rarely reduced to one spikelet; involucral bracts mostly leaf-like. Spikelets many- or few-flowered, flattened or terete, spicate or digitate at the ends of the ultimate branches or sometimes occupying the whole of the ultimate branches. Rachilla straight or flexuous, often bordered by hyaline or coloured membranous wings. Glumes distichous (very rarely spiral), concave or keeled, keel usually green, all except the lowest 2 or 1 subequal and containing bisexual flowers or the terminal one sometimes male. Hypogynous bristles absent. Stamens 1–3. Style 2- or 3-fid, continuous with ovary, not thickened at base, deciduous.

Nut trigonous or lenticular, glabrous, smooth or punctulate, rarely coarsely reticulate or transversely elongated.

Photo Geoff Sainty

Photo J. R. Hosking

Photo John R. Hosking

Distribution and occurrence: World: c. 600 species, cosmopolitan. Australia: c. 150 species (c. 50 species endemic), all States.

This genus is taken here in the broad sense to include species sometimes assigned to segregate genera such as Kyllinga and Pycreus. The tribe Cypereae is undergoing further study to assess whether segregate genera (including Lipocarpha) should be accepted.

Text by K. L. Wilson (1993, edited May 2009, March 2014)
Taxon concept:

Taxa not yet included in identification key
Cyperus leptocarpus,    Cyperus sp. Stockton (K.L.Wilson 10541)

 Key to the species 
1Style 3-fid; nut 3-angled in cross-section (more or less trigonous)2
Style 2-fid; nut lenticular, biconvex, plano- or concavo-convex106
2Dwarf annuals smelling of fenugreek (at least when dried)3
Annuals or perennials but not smelling of fenugreek
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3Spikelets flattened, with glumes arranged distichously; nut a third to half as long as glumeCyperus squarrosus
Spikelets more or less angular, with glumes arranged spirally; nut about two-thirds as long as glume
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Cyperus hamulosus
4Spikelets with 4 or more flowers, flattened and with glumes overlapping at least a quarter the length of the glume immediately above on the same side of the rachilla and often spreading widely (at least at maturity)5
Spikelets 1–3-flowered, or up to 16-flowered but then terete and with glumes remote (i.e. with glumes not or scarcely overlapping the glume immediately above on the same side of the rachilla) and closely appressed to rachilla
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5Spikelets arranged spicately on the rachis of the ultimate branches of the inflorescence, in very short to elongated spikes6
Spikelets digitately or subdigitately clustered, in clusters sometimes dense on a much reduced rachis, sometimes very few in number or solitary and then often appearing lateral when the lowest bract is erect
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6Culms 2–5 m high; inflorescence with 100–250 primary branches of similar lengthCyperus papyrus
Culms less than 2 m high; inflorescence with fewer than 15 primary branches, usually of varying length
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7Rachilla of the spikelet distinctly winged, the wings sometimes falling later8
Rachilla not winged or with very narrow wings
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8Involucral bracts (and associated branches) distinctly separated on axis from neighbouring bracts by up to 3 mm; perennial producing numerous globose, bulb-like tubers with deciduous stiff, smooth, shining, blackish coatsCyperus bulbosus
Involucral bracts and branches inserted very closely together; perennials, rarely producing tubers (and these grey-brown, oblong or ellipsoid or globose, with more or less persistent fibrous, dull, yellow-brown to grey-brown coats)
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9Spikelets fewer than 20 per spike10
Spikelets usually more than 20 per spike, numerous to very numerous
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10Spikelets more than 1.5 mm wide in side view, more or less flattened; plants often with tuber-bearing rhizomes11
Spikelets 1–1.5 mm width/diam., flattened to terete; rhizome, if present, not tuber-bearing
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11Perennials with short rhizome, not tuber-bearing; glumes pale red-brown with broad white or yellowish margins or yellow-brown to dark golden brown or straw-coloured tinged red-brown; spikelets suberect or spreading in loose hemispherical to globose clusters12
Perennials with slender, creeping rhizomes producing fibrous-coated tubers 5–10 mm diam.; glumes orange-brown to dark red-brown or yellow-brown, with narrow hyaline or whitish margins; spikelets spreading in short, broad-cylindrical spikes
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12Glumes pale red-brown with broad white or yellowish margins; spikelets suberect and held close to rachis in long, narrow-cylindrical spikes; leaves not septate-noduloseCyperus nutans
Glumes yellow-brown to dark golden brown or straw-coloured tinged red-brown; spikelets spreading in loose hemispherical to globose clusters; leaves often septate-nodulose
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13Spikelets 1.2–2 mm wide in side view; inflorescence compound; nut very narrow-ellipsoidCyperus betchei
Spikelets 2–4.5 mm wide in side view; inflorescence simple or with a few secondary branches; nut obovoid or narrow-obovoid to broad-ellipsoid
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14Nut grey to black; glumes with excurved mucro 0.3–0.8 mm longCyperus clarus
Nut yellow-brown; glumes with straight mucro
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15Glumes with mucro 0.1–0.3 mm long; perennial; leaf and involucral bract margins with more or less irregularly spaced and shaped prickles; on sandy-loam soilsCyperus fulvus
Glumes with mucro 0.2–0.5 mm long; annual or short-lived perennial; leaf and involucral bracts with more or less regular antrorsely aculeate prickles; on clayey soils
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Cyperus isabellinus
16Culms terete below, trigonous near the apex; leaves rarely half as long as culms; lowest involucral bract erect, very much exceeding the inflorescence, usually pushing it to one side; nut when mature 2–3 times as long as broad; freely fruitingCyperus victoriensis
Culms trigonous throughout their length; leaves mostly a half to three-quarters as long as culms; inflorescence symmetrical; nut either c. 1.5 times as long as broad or rarely maturing
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17Rachis of spikes often spinulose; spikelets 5–12 mm long, obtuse; glumes yellow to dark golden brown, 3–5-nerved on each side, very obtuse; tubers globose to ovoid, with grey tomentum at maturity;rhizomes yellow-brownCyperus esculentus
Rachis of spikes usually not spinulose (occasionally sparsely so); spikelets 10–30 mm long, acute or obtuse; glumes red-brown to dark red-brown, with up to 3 nerves on each side, obtuse or acute;tubers more or less ellipsoid, without tomentum; rhizomes purplish to dark brown
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18Lowest involucral bract shorter or not much longer than the inflorescence; spikelets c. 2 mm wide when mature; glumes usually dark red-brown, obtuse; the midrib faintly curved and recurved in side view from base to apex; fruit rarely maturing; fibrous coats of tubers soon disintegrating, not usually persisting beyond the first yearCyperus rotundus
Lowest bract much exceeding the inflorescence; spikelets 2.5–3 mm wide in side view when mature; glumes various shades of brown, rarely very dark, acute; midrib straight in side view from immediately above the base to the apex; nut c. 1.5 times as long as broad, obovate to elliptic-obovate; freely fruiting; fibrous coats of tubers often persisting into the second year
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Cyperus bifax
19Inflorescence compound; glumes yellow-brown; nut 1.9–2.2 mm long, nearly as long as glumeCyperus betchei
Inflorescence simple; glumes red-brown or greenish tinged red-brown; nut 1.2–1.7 mm long, about half as long as glume
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Cyperus subulatus
20Glumes 1–1.5 mm longCyperus exaltatus
Glumes 2–6.5 mm long
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21Leaves and bracts septate-nodulose (often only obvious when dried)22
Leaves not septate-nodulose
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22Terminal spikes cylindrical or ovate-cylindrical, laterals smaller, divergent or deflexed23
Terminal spikes hemispherical to globose, usually dense, 1–2 cm wide in side view; glumes 2–2.5(–3) mm long
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Cyperus gunnii
23Glumes 4–6.5 mm long, red-brown; spikelets 4–10-floweredCyperus lucidus
Glumes 2.5–4 mm long, pale brown; spikelets 2–5-flowered
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Cyperus vorsteri
24Spikelets 10–28 mm long, 8–24-flowered; tufted perennial, often apparently annual, often without any rhizomeCyperus congestus
Spikelets 6–15 mm long, 7–14-flowered; rhizomatous perennial; rhizome short and thick
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25Glumes pale red-brown, with midrib green, 2–2.5 mm long; spikelets suberect, 1.5–2.0 mm wide in side viewCyperus nutans
Glumes whitish to pale brown on the sides, 3–3.5 mm long; spikelets spreading, 2–2.5 mm wide in side view
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Cyperus rigens
26Glumes obtuse in side view but sometimes apparently acute because of the presence of a short mucro27
Glumes more or less acute in side view
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27Glumes 1–2 mm long; spikelets flattened; tufted annualCyperus iria
Glumes 2–3.5 mm long; spikelets flattened or terete; rhizomatous perennials
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28Glumes without broad whitish margins, short-mucronate; bracts and leaves septate-nodulose in the dried state, thick-textured; spikes rather dense29
Glumes with broad whitish margins above; bracts and leaves not septate-nodulose, thin-textured; spikes broad-ovoid, loose
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Cyperus procerus
29Nut red-brown, minutely tuberculate; leaves to 12 mm wideCyperus alterniflorus
Nut yellow-brown, smooth to colliculate; leaves to 7 mm wide
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Cyperus gunnii
30Rachis minutely and densely hispidCyperus pilosus
Rachis not hispid
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31Glumes white to dark golden brown or straw-coloured tinged red-brown32
Glumes red-brown
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32Glumes with excurved mucro 0.3–1 mm long33
Glumes without mucro, or mucro straight and no more than 0.3 mm long
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33Nut less than half as long as glume; annual with thin-textured leaves and bracts, not septate-noduloseCyperus compressus
Nut at least half as long as glume; slender perennial with tough-textured leaves and bracts, often obviously septate-nodulose when dried
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Cyperus clarus
34Nut yellow-brown, nearly as long as glume; glumes 2–3 mm long; leaves and bracts tough-textured, often obviously septate-nodulose when driedCyperus fulvus
Nut dark red-brown, less than half as long as glume; glumes 3–3.5 mm long; leaves and bracts thin-textured, not septate-nodulose
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Cyperus rigens
35Leaves and bracts tough-textured, flat or folded, margins and midribs scabrous; lowest involucral bract suberect; rhizomatous perennial with solitary culmsCyperus lhotskyanus
Leaves and bracts thin-textured, flat or with revolute margins; lowest involucral bracts spreading; tufted perennial, often apparently annual and without a rhizome
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Cyperus congestus
36Involucral bracts all much shorter than inflorescence; plant resembling miniature papyrusCyperus prolifer
One to 22 involucral bracts longer than inflorescence; plants not resembling miniature papyrus
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37Involucral bracts 6–22 exceeding inflorescence (rarely only as long as inflorescence)38
Involucral bracts 1–5 exceeding inflorescence
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38Leaves all or mostly reduced to sheaths39
Leaves with well-developed blade
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39Involucral bracts 12–22 exceeding inflorescence; glumes c. 2 mm longCyperus involucratus
Involucral bracts 6–9 exceeding or as long as inflorescence; glumes 1–2.5 mm long
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40Glumes 2–2.5 mm longCyperus vaginatus
Glumes 1–1.3 mm long
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Cyperus filipes
41Inflorescence with few (1–9, rarely to 15 in Cyperus vaginatus) spikelets per loose cluster42
Inflorescence with numerous spikelets per dense globose cluster
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42Leaves with 2 prominent, whitish (at least when dried) lateral veins; glumes straw-coloured to pale brown, 1–1.5 mm long; rachilla winged; leaf sheaths purplish red at baseCyperus albostriatus
Leaves with only midvein prominent; glumes red-brown to blackish; rachilla not winged; leaf sheaths purplish red or pale yellow-brown at base
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43Nut ellipsoid; leaf sheaths purplish red at base; glumes very dark red-brown to blackish, 1.5–2 mm longCyperus tetraphyllus
Nut ovoid; leaf sheaths pale yellow-brown at base; glumes red-brown, 3–3.5 mm long
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Cyperus rupicola
44Inflorescence with numerous branches; culms 25–90 cm highCyperus eragrostis
Inflorescence head-like; culms 1–20 cm high
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Cyperus pygmaeus
45Leaves all or mostly reduced to sheaths with a rudimentary blade46
Leaves with well-developed blade
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46Culms and involucral bracts firm to rigid; culms terete to trigonous47
Culms and involucral bracts soft-textured (easily compressed between the fingers); culms triquetrous
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Cyperus haspan
47Involucral bracts mostly 5–8 in number, always more than 5 cm and up to 15 cm long, flat, firm-textured, not pungent; inflorescence simple to compound with 4–12 branches to 6 cm long, bearinghemispherical clusters of spikelets, or occasionally loosely head-likeCyperus vaginatus
Involucral bracts 2–4, usually less than 5 cm long, very rigid and pungent with incurved margins; inflorescence head-like or with 1–3 short branches to 2 cm long, bearing globose clusters ofspikelets
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Cyperus gymnocaulos
48Nut trabeculate and striateCyperus mirus
Nut smooth or minutely roughened
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49Glumes less than 2 mm long (excluding any long mucro)50
Glumes 2 mm or more long (excluding any long mucro)
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50Glumes with sides evenly red-brown to dark red-brown or blackish (midribs mostly green)51
Glumes uniformly green or with sides hyaline, white, pale brown, yellow or golden brown, occasionally with a red-brown patch (midribs mostly green)
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51Rachilla wingedCyperus rigidellus
Rachilla not winged
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52Spikelets numerous in the dense globose clusters53
Spikelets few (1–12) in the loose, ovoid to hemispherical clusters
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53Glumes 0.6–0.9 mm longCyperus difformis
Glumes at least 1.0 mm long
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54Glumes 1.5–2 mm longCyperus reflexus
Glumes 1.0–1.4 mm long
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Cyperus castaneus
55AnnualCyperus castaneus
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56Glumes red-brownCyperus haspan
Glumes dark red-brown to blackish
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57Inflorescence compound; nut c. 0.5 mm long, less than half as long as glumeCyperus concinnus
Inflorescence simple; nut 1.3–1.5 mm long, nearly as long as glume
                       Back to 56
58Glumes acute, dorsally straight in side viewCyperus disjunctus
Glumes obtuse, shortly mucronate, dorsally strongly curved in side view
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Cyperus tetraphyllus
59Inflorescence compound to decompound with numerous clusters of spikelets; glumes evenly yellow to golden brown; leaves strongly septate-nodulose, thick-textured; robust perennialCyperus dactylotes
Inflorescence simple with 1–8 clusters of spikelets; glumes not evenly yellow to golden brown (occasionally with yellowish patches); leaves not or rarely slightly septate-nodulose but then thin-textured; slender perennials or annuals
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60Glumes with 2–6 nerves on each side61
Glumes with 1 nerve or no nerves on each side
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61Spikelets with upper flowers female, lower flowers maleCyperus semifertilis
Spikelets with all flowers usually bisexual
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62Involucral bract 1, erect; inflorescence of 1–4 spikelets; dwarf annualIsolepis levynsiana
Involucral bracts 2–4, erect to spreading; inflorescence with 1–25 spikelets; small perennials or annuals
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63Spikelets 2.5–4 mm wide in side view; nut pale brownCyperus rigidellus
Spikelets 2–2.5 mm wide in side view; nut dark brown
                       Back to 62
64Glumes strongly excurved; inflorescence of 1–5 spikeletsCyperus sculptus
Glumes dorsally slightly incurved in side view to slightly excurved; inflorescence of 12–25 spikelets
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65Nut broad-obpyriform to broad-obovoid, with globose bulge near base of persistent style baseCyperus enervis
Nut ellipsoid to broad-ellipsoid, without persistent dilated style base
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Cyperus eglobosus
66Keel of glumes a broad band about as wide as thinner-textured side of glume67
Keel of glumes a narrow band, much narrower than sides of glume
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67Tufted annuals; midrib of glumes with larger, more isodiametric cell outlines than on sides68
Perennials, shortly rhizomatous, often with fibrous remains of leaf sheaths at base; midrib and sides of glumes with similar cell outlines
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68Spikelets 2–2.5 mm wide in side view; glumes 1–1.5 mm longCyperus flaccidus
Spikelets c. 3 mm wide in side view; glumes 1.5–2 mm long
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Cyperus aquatilis
69Glumes c. 1.5 mm long, longer than broad; stamens 3Cyperus trinervis
Glumes 1–1.3 mm long, about as long as broad; stamens 2
                       Back to 67
Cyperus stradbrokensis
70One involucral bract longer than inflorescence; base of style inconspicuous (not thickened)71
Two to four involucral bracts longer than inflorescence; base of style thickened compared to rest of style and obviously persistent on fruit
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71Glumes more or less straight dorsally from shortly above base in side view, 1.7–2 mm long, 0.7–1 mm wide in side view; inflorescence usually a single sessile cluster of spikelets (rarely with 1 or 2 very short branches)Cyperus laevis
Glumes strongly curved dorsally in side view, with excurved apex, 1.5–1.7 mm long, c. 0.5 mm wide in side view; inflorescence usually with 1–4 short branches
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Cyperus imbecillis
72Base of style erect; nut broad-obovoid, nearly as long as the glume; glume keel smoothCyperus enervis
Base of style strongly recurved; nut ellipsoid, c. 2/3 as long as glume; glume keel minutely toothed towards apex
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Cyperus curvistylis
73Nut with paler corky, thickened anglesCyperus platystylis
Nut without corky, thickened angles
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74Nut ovoidCyperus rupicola
Nut obovoid to ellipsoid
                       Back to 73
75Glumes with sides uniformly yellow to red-brown76
Glumes with sides uniformly green, whitish, pale brown, or with red-brown patch
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76Glumes with midrib about as wide as sides and with cell outlines larger than on sides, 1-nerved only at edge of midribCyperus eragrostis
Glumes with midrib much narrower than sides and with cell outlines similar to those of sides, with 2–4 nerves on each side
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77Leaves and bracts strongly curly at least near apex78
Leaves and bracts straight to slightly curved
                       Back to 76
78Anthers 1.3–1.6 mm long; glume mucro no more than 0.1 mm longCyperus secubans
Anthers 0.3–1.2 mm long; glume mucro 0.1–0.8 mm long
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79Glumes evenly yellow to golden brown, with mucro 0.3–0.8 mm long (usually excurved); nut grey to blackCyperus clarus
Glumes straw-coloured to golden brown and with dull red-brown patches, with straight mucro 0.1–0.3 mm long; nut pale yellow-brown
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80Leaf marginal prickles erect, papillose; leaf sheaths pinkish to purple-red; nut tuberculate or colliculateCyperus rigidellus
Leaf marginal prickles either mixed strongly flabellate to erect aculeate or antrorsely aculeate; leaf sheaths pale yellowish with red-brown blotches; nut colliculate to smooth and reticulate-areolate
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Cyperus fulvus
81Nut red-brown to black or grey, tuberculate (occasionally smooth in Cyperus gilesii)82
Nut yellow-brown to dark golden brown, smooth to colliculate or pitted
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82Anthers 1.1–1.8 mm long; nut narrow-ellipsoid to narrow-obovoid, red-brownCyperus alterniflorus
Anthers 0.3–0.8 mm long; nut very narrow-ellipsoid or obovoid, red-brown to blackish or grey to black
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83Nut very narrow-ellipsoid, red-brown to blackish; glumes very narrow-elliptic to narrow-ovateCyperus gilesii
Nut obovoid, grey to black; glumes elliptic to ovate
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Cyperus clarus
84Prickles on leaf margins antrorsely aculeate, more or less regularly spaced85
Prickles on leaf margins mixed aculeate to papillose, antrorse to erect and flabellate, more or less irregularly spaced
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85Glumes dark red-brown or rarely straw-coloured; spikelet clusters dense; leaves exceeding or as long as culmsCyperus gunnii
Glumes yellow to dark golden brown; spikelet clusters loose; leaves shorter than to as long as culms
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86Glumes 2.5–3.4 mm long; glume spacing 1.6–2.3 mmCyperus betchei
Glumes 1.3–2.1 mm long; glume spacing 0.9–1.3 mm
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Cyperus dactylotes
87Anthers 0.3–1.2 mm longCyperus fulvus
Anthers 1.3–2.0 mm long
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88Long-rhizomatous, with culms usually solitary along rhizome; leaves V-shaped in cross section, with midrib obvious abaxially, with marginal prickles irregularly spaced; plants never viscidCyperus lhotskyanus
Very shortly rhizomatous, with culms tufted; leaves canaliculate, with midrib not obvious, with marginal prickles regularly spaced; plants often viscid
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Cyperus secubans
89Spikelets less than 2.5 mm wide in side view90
Spikelets 2.5–5 mm wide in side view
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90Inflorescence a single cluster of 1–14 spikelets91
Inflorescence simple to compound, with 3–8 primary branches and numerous spikelets
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Cyperus fulvus
91Glumes 3- or 4-nerved on each side; apex excurved in side viewCyperus gracilis
Glumes 1- or 2-nerved on each side; apex more or less straight in side view
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Cyperus enervis
92Glumes with midrib about as wide as sides and with cell outlines larger than on sides, nerved only at edge of midribCyperus eragrostis
Glumes with midrib much narrower than sides and with cell outlines similar to those of sides, with 2–4 nerves on each side
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93Nut dark brown to black, less than half as long as glume; leaves never curly; plant never viscidCyperus compressus
Nut pale yellow-brown, three-quarters to seven-eighths as long as glume; leaves often curly towards apex; plants occasionally viscid
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94Culms 3–25 cm long; leaves not septate-nodulose; leaf sheaths pinkish to purple-red near baseCyperus rigidellus
Culms 25–50 cm long; leaves mostly septate-nodulose; leaf sheaths pale yellowish or straw-coloured with occasional red-brown patches
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Cyperus fulvus
95Inflorescence of 1–6 sessile spikes, rarely with 1–3 short branches to 1.5 cm long96
Inflorescence simple or compound with spikes on 3–14 branches to 20 cm long (rarely head-like in Cyperus leiocaulon)
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96Bases of culms bulbously swollen; glumes acute; flowers 1–3 per spikeletCyperus aggregatus
Bases of culms apparently enlarged for some distance because of persistent, whitish, thin-textured leaf sheaths; glumes obtuse; flowers 3–6 per spikelet
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Cyperus dubius
97Culms and axes of inflorescence hispid or papillose-scabrous98
Culms and axes of inflorescence smooth
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98Culms and rachis of inflorescence hispid-scabrous, green; leaves septate-noduloseCyperus scaber
Culms and rachis of inflorescence papillose-scabrous, greyish; leaves not septate-nodulose
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Cyperus conicus
99Spikelets c. 0.5 mm diam. when mature100
Spikelets 0.7–2.5 mm diam. when mature
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100Glumes 2.3–2.7 mm long; spikelets 3–6-flowered; base of culms not enlarged101
Glumes 3–3.5 mm long; spikelets 1–3-flowered; base of culms bulbously enlarged
                       Back to 99
Cyperus cyperoides
101Spikelets spreading at 90–140° from the vertical; culms rigid, erect, 2–4 mm diam.Cyperus dietrichiae
Spikelets spreading at 40–90° from the vertical; culms lax, c. 1 mm diam.
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Cyperus bowmannii
102Spikelets breaking up at maturity and dispersing as individual corky internodes of the rachilla with associated glume and nutCyperus odoratus
Spikelet falling as a complete unit at maturity
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103Leaves strongly septate-nodulose; robust perennials to c. 170 cm tall; inflorescence compound; involucral bracts (5-)8–13 exceeding inflorescence104
Leaves not septate-nodulose; slender perennials to c. 50 cm tall; inflorescence simple; involucral bracts 1–8 exceeding inflorescence
                       Back to 102
104Glumes 2.5–4 mm long, pale brown; nut 1.8–2.3 mm long, dark yellow-brown; spikelets 2.5–5 mm long, 2–5-floweredCyperus vorsteri
Glumes 4–6.5 mm long, red-brown to dark red-brown; nut 2.5–3 mm long, dark grey-brown to blackish; spikelets 4–20 mm long, 4–10-flowered
                       Back to 103
Cyperus lucidus
105Involucral bracts 2 exceeding inflorescence; flowers 5–16 per spikeletCyperus subulatus
Involucral bracts 3–5 exceeding inflorescence; flowers 2–4 per spikelet
                       Back to 103
Cyperus leiocaulon
106Spikelets several- to numerous-flowered107
Spikelets 1-flowered, but sometimes with a second imperfect flower above, whole spikelet falling as a unit at maturity
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107Each spikelet falling as a unit at maturityCyperus bracheilema
Each spikelet with rachilla persistent and glumes falling individually at maturity
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108Inflorescence pseudolateral, sessile; lowest involucral bract erect, appearing as a continuation of the rush-like culmCyperus laevigatus
Inflorescence obviously terminal, branched or head-like; involucral bracts not as above
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109Nut dorsally flattened with a flat or concave face against the rachilla; inflorescence densely head-like, subglobose, with 5–7 or more involucral bracts exceeding inflorescenceCyperus pygmaeus
Nut laterally flattened, with one edge against the rachilla; inflorescence loosely head-like or branched, with 1–4 involucral bracts exceeding inflorescence
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110Glumes 3.5–4.5 mm long, acute; spikelets 3.5–5 mm wide in side viewCyperus unioloides
Glumes less than 3 mm long, obtuse (occasionally broad-acute in Cyperus polystachyos); spikelets 1–3 mm wide in side view
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111Glumes with excurved mucro 0.3–0.7 mm long; glume-spacing c. 0.5 mmCyperus nervulosus
Glumes not mucronate or scarcely mucronulate; glume-spacing c. 1 mm
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112Glumes incurved dorsally in side view, dark red-brown to blackish, often with a hyaline patch on sidesCyperus sanguinolentus
Glumes more or less straight dorsally in side view, yellow to very dark yellow-brown, occasionally red-brown in Cyperus polystachyos and C. flavidus but never with a hyaline patch
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113Spikelets suberect, usually densely crowded in obconical subdigitate clusters; rachilla narrowly wingedCyperus polystachyos
Spikelets spreading widely, in loose, shortly spicate to subdigitate clusters; rachilla not winged
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114Nut with faint whitish transverse wrinklesCyperus flavescens
Nut minutely puncticulate
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Cyperus flavidus
115Tufted annual or perennial with or without a very short rhizome; inflorescence whitish or very light green; nut black at maturity; stamens 2Cyperus sesquiflorus
Perennial with creeping rhizomes, to 30 cm long but occasionally very short; inflorescence greenish or yellow-tinged; nut yellowish becoming brown at maturity
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116Inflorescence more or less ovoid, dense, solitary or with 2 smaller ones at the base; spikelets numerous, sometimes 100 in number, 1-flowered; midrib of the glumes usually toothed; stamens 1 or 2 (rarely 3)Cyperus brevifolius
Inflorescence globose, loose, always solitary; spikelets not usually more than 50, a second imperfect flower often present; midrib of the glumes usually smooth or nearly so, rarely toothed; stamens 3 (rarely 2)
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Cyperus sphaeroideus

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