X
Jump to key:

Click the number at the start of a key lead to highlight both that lead and its corresponding lead. Click again to show only the two highlighted leads. Click a third time to return to the full key with the selected leads still highlighted.

Click images to enlarge and show more photo credit.

Key to Cyperus

Cyperaceae

Cyperus

Copy permalink to share

  2 Leaves many, cauline, coriaceous, closely spaced distally; culms arising from long, thick, branched rhizomes; inflorescence dense, capitate; [FL, beaches and coastal dunes]; [section Remirea]
  2 Leaves basally disposed; inflorescence of 1-5 sessile ovoid spikes, or more diffuse.
    3 Spikelets many, in densely globose to pyramidal heads, these borne on elongate rays or sessile; rhizomatous perennials, forming extensive floating mats; [section Oxycaryum]
    3 Spikes [actually consisting of numerous highly reduced, spirally imbricate spikelets each with 1-2 (-3) scales] 1-5, terminal and capitate on the culm; terrestrial, often diminutive annuals; [subgenus Lipocarpha].
1 Floral scales 2-ranked and distichously imbricate.
      4 Spikelets reduced, 1(-2)-flowered with 2-3 scales, flattened, ovoid or lanceoloid, mostly < 5 mm long; rays absent, spikes 1-4, very dense, ovoid to oblong; stigmas 2; achenes biconvex; [subgenus Kyllinga].
      4 Spikelets 1-many-flowered (if all only 1-3-flowered then subterete to quadrangular in cross-section and ellipsoid to linear); rays present or absent, inflorescence mostly not as above.
        5 Stigmas 2; achenes laterally flattened, lenticular (to compressed-subterete), borne with an edge to the rachilla, spikelets thus laterally flattened.
(c) Horn, Jay
(c) Horn, Jay
          6 Achene emarginate or obcordate at apex; rachilla deciduous, basally articulate; spikelets ovate-lanceolate, with 4-6(-8) fertile scales, these shortly but distinctly mucronate [introduction, FL]; [subgenus Queenslandiella]
        5 Stigmas 3 (2 in subg. Juncellus species, sometimes 2 and 3 in C. alopecuroides); achenes either trigonous or dorsiventrally compressed and borne with a face to the rachilla; spikelets terete or quadrangular to strongly compressed-quadrangular or compressed-subterete.
             7 Rachilla corky-thickened, transversely articulated at the base of each scale, the spikelets at maturity separating into 1-fruited dispersal units, each with 1 scale, the rachilla segment and wings, conspicuously clasping the achene (spikelets visibly “jointed”, at maturity breaking apart); spikelets linear, terete or scale tips slightly spreading.
               8 Spikelets 2-8, rays absent (the spikelets in a single digitate cluster at the top of the culm, appearing lateral); bracts 2-3, longest erect, filiform, ≤ 1 mm wide [pine rocklands, s. peninsular FL]; [section Filiformes, apparently allied with C. fuligineus]
               8 Spikelets 10-60, rays usually present and well-developed; bracts 4-10, spreading to ascending, mostly leafy, ≥1mm wide. [widespread, often weedy]; [section Diclidium]
                 9 Tip of each scale not reaching above the base of the next distal scale on the same side of the rachilla, and usually ending short of it; achene linear-oblong, 1.5-2 mm long, ca. 3× as long as wide.
                 9 Tip of each scale surpassing the base of the next distal scale on the same side of the rachilla; achene ellipsoid or obovoid-oblong, 1-1.5 mm long, ca. 2× as long as wide
             7 Rachilla not transversely articulated; scales persistent or deciduous; rachilla wings present or absent, not corky, clasping the achene or not; spikelets ovoid to linear, compressed, quadrangular, or terete.
                   10 Spikelets in spikes (sometimes sessile and capitate), arranged along a well-developed rachis, this sometimes obscured but evident upon dissection; spikelets quadrangular or terete to moderately compressed.
                     11 Longest bract vertical, appearing as a continuation of the culm; rays absent, spikelets 2-7(-14), in a single digitate cluster; achenes dorsiventrally compressed, with the achene face toward the rachilla, the spikelets subterete (elliptic in cross-section) [rare waif, brackish marshes]; [subgenus Juncellus, section Laevigati]
Click images to enlarge and show more photo credit.

Key to Cyperus, Key A: Key to subgenus Lipocarpha

Copy permalink to share | Check for keys that lead to this key

1 Inflorescence terminal, the bracts 2-3, deflexed to ascending; spikes (1-) 2-5, each 2-10 (-12) mm long; achenes narrowly obovoid, 3.3-5× as long as wide; anthers ca. 0.25 mm long, or longer; [section Lipocarpha]
  2 Scale apex (the outer 0.2-0.3 mm) excurved, acuminate; stigmas 2; anthers ca. 0.25 mm long
  2 Scale apex straight to incurved; stigmas 3; anthers ca. 0.5 mm long
1 Inflorescence appearing lateral, the bracts 1-2 (-3), the longest held vertical and appearing as a continuation of the culm; spikes 1-2 (-3), each 1-5 (-8) mm long; achenes obovoid or ellipsoid, 1.5-2.5× as long as wide; anthers 0.1-0.2 mm long.
    3 Stigmas 3; outer scales ca. 2 mm long, the greenish midrib projecting as a long, excurved cusp; plants relatively robust, culms 5-30 cm tall, ca. 0.7 mm thick; [rare waif, FL]; [section Rikliella]
    3 Stigmas 2; outer scales 0.5-1.6 mm long, acute to acuminate, incurved to slightly excurved; plants diminutive, culms 2-15 (-20) mm tall, 0.3-0.5 mm thick; [collectively widespread]; [section Neohemicarpha]
      4 Outer scale 0.5-1 mm long; inner scale bifid, to 0.2 mm long or absent; [widespread in our region]
      4 Outer scale 0.9-1.6 mm long; inner scale oblong, 0.5-0.8 long; [IL and LA westwards].
        5 Outer scale widest about at mid-length, acuminate, excurved; inner scale usually veinless (rarely with 2-4 reddish veins)
        5 Outer scale widest above mid-length, mostly acute, incurved; inner scale with 2-4 reddish veins
Click images to enlarge and show more photo credit.

Key to Cyperus, Key B: Key to subgenus Kyllinga

Copy permalink to share | Check for keys that lead to this key

(c) Horn, Jay
1 Scale keel conspicuously winged, laciniate; anthers 2 mm long; achenes ca. 1.2 mm wide, ovate to nearly orbicular; fibrous-rooted annual; [section Kyllinga]
1 Scale keel toothed or entire; anthers <2 mm long; achenes 0.5-1 mm wide, elliptic to obovate or oblong; perennials (except C. hortensis); [section Brevifoliae].
  2 Plants with culms arising singly along a scaly, creeping rhizome; spikes green.
    3 Central spike 8-10 mm wide, globose, solitary; inflorescence bracts deflexed to spreading (divaricate); style 0.6-1.2 mm long; anthers 2-3; scale keel entire
    3 Central spike 3-7 mm wide, ovoid to oblong, often branched; longest inflorescence bract held vertical on most culms; style 1.8-2.2 mm long; anther 1; scale keel denticulate
  2 Plants cespitose or with very slender, easily broken stolons and cormose culm bases; spikes white (except C. hortensis).
      4 Spikes green; plants cespitose, fibrous-rooted annuals; scale keels denticulate; achene light brown, oblong, 2× as long as wide
      4 Spikes whitish; plants cespitose or stoloniferous perennials; scale keels entire; achenes various.
        5 Mature achene light brown, oblong to obovate; plants reproducing by very slender, easily broken stolons; spikes ovoid to pyramidal.
        5 Mature achene black, with whitish (pale) stipe and apiculus, broadly elliptic; plants cespitose; larger (central) spikes oblong to cylindric.
Click images to enlarge and show more photo credit.

Key to Cyperus, Key C: Key to subgenus Pycreus – stigmas 2; achenes lenticular;
achenes laterally flattened, borne with an edge toward the rachilla

Copy permalink to share | Check for keys that lead to this key

1 Scales obtuse to slightly mucronate, apex not notably excurved; achenes (0.7-)1-1.6 mm long.
  2 Floral scales divaricate (thus the spikelet margin appearing coarsely dentate), with whitish or hyaline margins; coarse, erect plants 30-75cm tall, inflorescence diffuse; [section Albomarginati]
  2 Floral scales with tips appressed (proximal sometimes spreading in C. polystachyos), lacking hyaline border; plants mostly smaller.
(c) Horn, Jay
    3 Achenes oblong, subterete, often only slightly compressed, apex truncate, apiculate; scales 3-5-nerved; spikelets mostly <2 mm wide (except C. filicinus); [section Pycreus].
      4 Scales 2.5-3.6 mm long, 1.6-1.8 mm wide; achenes 1.2-1.6 mm long, 0.6-0.9 mm wide, narrowly obovoid; [beaches, maritime habitats]
      4 Scales 1.3-2.4 mm long, 1.0-1.4 mm wide; achenes 0.8-1.2 mm long, 0.4-0.6 mm wide; [habitats various]
        5 Cespitose annual, < 12 cm tall; floral scales ovate, 1.3-1.6 mm long, loosely imbricate; styles 0.1-0.2 mm long; stigmas 0.3-0.4 mm long; filaments 1.2-1.4 mm long; anthers 0.1-0.2 mm long; achenes stipitate, strongly compressed laterally; [LA and westwards, rare]
        5 Shortly rhizomatous perennial, mostly > 12 cm tall; floral scales oblong, 1.8-2.4 mm long, closely imbricate; styles 0.6-1 mm; stigmas 1.4-2 mm long; anthers 0.6-0.8 mm long; achenes substipitate to cuneate, slightly compressed laterally; [widespread]
(c) Horn, Jay
    3 Achenes ovoid, ellipsoid, or obovoid, biconvex, apex rounded to acute; scales bicarinate medially; spikelets mostly > 2mm wide.
(c) Horn, Jay
          6 Achenes black to dark reddish brown, with encrusted transverse whitish lines, epidermal cells longitudinally elongate, rectangular; scales pale brown or yellowish, the dark achenes strongly contrasting and visible through the spikelets in life (without backlighting); fibrous-rooted annuals; [section Zonati].
          6 Achenes black to brownish, without transverse lines, epidermal cells square or isodiametric; plants either perennials or scales darker.
             7 Scales uniformly pale yellowish to yellowish brown; cespitose perennials, rhizomes short; [section Propinqui].
               8 Anthers ellipsoid, 0.3-0.6 mm long; spikelets 1.8-3 mm wide, with scales 1.8-2.6 mm long; achenes brown, ellipsoid, ovoid, or obovoid, 0.4-0.8 mm wide; [more widespread]
               8 Anthers linear, 2-2.4 mm long; spikelets 3-5 mm wide, with scales (3.6-) 3.8-4.2 (-4.6) mm long; achenes black, broadly obovoid to orbiculate, 0.8-1 mm wide; [s. peninsular FL, rare waif]
             7 Scales with anthocyanic (reddish-brown or purplish) pigmentation; fibrous-rooted annuals (except C. sanguinolentus); [section Vestiti].
                 9 Floral scales firmer, subcoriaceous, not bilaterally sulcate; reddish pigmentation ±uniformly distributed or concentrated basally and medially; floral scales 2.5-3 mm long; annuals, culms usually <25 (35) cm long
                 9 Floral scales membranous, each side with a narrowly elliptic, shallow, pale, translucent groove outlined at least marginally by reddish pigmentation; floral scales 1.8-2.7 mm long; annuals or perennials.
                   10 Cespitose annuals, culms usually < 25 (-35) cm tall; stamens 2; style divided nearly to base; style branches conspicuously exserted beyond floral scale, exposed portions about as long as floral scale
                   10 Rhizomatous perennials, culms usually > 25 cm tall; stamens 3; style divided less than half its length; style branches not so conspicuously exserted, exposed portions less than half as long as floral scale
Click images to enlarge and show more photo credit.

Key to Cyperus, Key D: Key to subgenus Pycnostachys -- stigmas 3; achenes trigonous; rachis essentially absent,
spikelets borne in digitate clusters or in umbellate or glomerulate heads

Copy permalink to share | Check for keys that lead to this key

1 Scales rounded to minutely mucronate (mucro <0.3mm), incurved to excurved.
  2 Leaves mostly reduced to bladeless sheaths; inflorescence bracts 18-22 subequal, large and conspicuous; [the “umbrella sedge” common in the nursery trade]; [section Alternifolii]
  2 Leaf blades present (absent in C. haspan and C. prolifer); inflorescence bracts 2-10 (rarely more, then markedly unequal).
    3 Scales with 1 central nerve on back, 2-keeled in lower 30-60%, nerves absent elsewhere or scales with 1 lateral rib on each side; spikelets with scales closely overlapping, aggregated into numerous dense glomerulate heads borne on elongate rays; [section Luzuloidei]
    3 Scales conduplicate their entire length, or broadly rounded on back, not 2-keeled as above, 5-11 nerved, medially 3-nerved, or occasionally with 2 indistinct lateral ribs and a single main keel nerve; spikelets in loose digitate clusters, or inflorescence congested into a single capitate cluster; [sections Fusci, Haspani, and Diffusi]
Click images to enlarge and show more photo credit.

Key to Cyperus, Key E: Key to subgenus Cyperus – stigmas 3; achenes trigonous; spikelets borne in spikes on a well-developed rachis;
rachilla continuous, or articulate only at the base

Copy permalink to share | Check for keys that lead to this key

1 Leaf blades absent; culms 15-50 mm thick, nearly terete; inflorescence open and diffuse, primary rays 10-30 cm long, bearing numerous 2nd and 3rd order rays up to 20 cm long and bracts to 25 cm long, often drooping; anther connectives subulate, projected beyond the anther 0.2-0.5 mm; [exotics, commonly cultivated, rarely naturalizing]; [subgenus Cyperus, section Papyrus]
  2 Rays stiff, ascending to erect; primary bracts (8-) 20-45 cm long
  2 Rays slender, drooping or arching; primary bracts 3-8 cm long
1 Leaf blades well-developed (except C. articulatus); culms < 20mm thick, trigonous if broader than 5 mm; inflorescence smaller, more congested (except C. prolixus); anther connectives not prolonged.
    3 Spikelets compressed-quadrangular or compressed-subterete, mostly 2× or more as wide as thick (less compressed in C. erythrorhizos and some forms of C. esculentus and C. rotundus); scales 1-many, deciduous or persistent; rachilla persistent or deciduous after the scales.
      4 Spikes long-cylindric, with (25-) 35-80+ spikelets, and well-developed branches or 2nd order rays; scales deciduous, minute, (1.1-) 1.3-1.8 mm long, (6-) 12-20 (-30) per spikelet; spikelets quadrangular, slightly compressed (subterete in C. alopecuroides); achenes (0.4) 0.7-1 (-1.2) mm long, often moderately dorsiventrally compressed or plano-convex; plants coarse perennials, culms 5-25 dm tall, 5-50 mm in diameter (C. erythrorhizos keyed under both leads).
        5 Stigmas 2, or 2 and 3 on a plant; spikes narrowly cylindric, the rachis obscured by the densely packed, ascending, imbricate spikelets; spikelets subterete, somewhat compressed, ovoid to oblong; rachilla wings absent to 0.1 mm wide; achene lenticular, its face against the rachilla [rare waif, FL]; [section Alopecuroides]
        5 Stigmas 3; spikes less dense, spikelets spreading to divaricate; spikelets quadrangular, linear; rachilla winged, wings 0.3 mm wide; achenes not as above [collectively widespread]; [section Fastigiati].
          6 Plants perennial, with indurate rhizomes (sometimes inconspicuous); roots not reddish; floral scales 1.6-1.8 mm long; anthers 0.4-0.5 mm long; culms robust, trigonous, 5-25 dm tall, 5-15 mm wide
          6 Plants annual; roots reddish, fibrous; floral scales 1.3-1.5 mm long; anthers 0.2-0.3 mm long; culms shorter, mostly rounded, (0.05-) 0.5-2.5 (-10.5) dm tall, 1-7.5 mm wide
      4 Spikes not as above; scales persistent or deciduous, mostly > 1.8 mm long (except sections Iriodei and Aristati); achenes > 1 mm long, trigonous (dorsiventrally compressed in C. nipponicus and C. serotinus); culms mostly < 10 dm tall, < 7.5 mm in diameter (except C. prolixus).
             7 Spikelets 1.2-1.5 (-1.6)mm wide, only compressed proximally, filiform distally; adjacent scales spaced apart on the same side of the rachilla; rachilla wings absent or very reduced; [subgenus Cyperus, section Distantes]
             7 Spikelets mostly broader, not filiform distally; scales apices reaching or exceeding the base of the next scale on the same side of the rachilla; rachilla wings present or absent.
               8 Scales strongly 5-nerved, obovate-orbiculate, 1-1.5 mm long, divaricate, scarcely overlapping, apex emarginate and mucronulate; style < 0.1 mm long; inflorescence diffuse, secondary rays present, spikelets widely spaced on elongate rachises; [weedy exotics]; [section Iriodei]
               8 Scales variously nerved, but at least 1.8 mm long (if shorter, with an excurved cusp > 0.5 mm long), not emarginate; style at least 0.5 mm long; inflorescence generally more congested.
                   10 Scales cuspidate to awned, midrib excurrent at least 0.3 mm, conspicuously excurved (straight in C. compressus and C. nipponicus); plants either diminutive fibrous-rooted annuals, culms often decumbent, or cespitose perennials (section Elegantes) with involute leaves and vegetative parts viscid (sticky).
                   10 Scales acute, midrib not notably projecting, apices not excurved; plants erect, rhizomatous, stoloniferous, cormose-based, or cespitose perennials, vegetative parts not viscid, leaves plane or V-shaped (cuspidate perennial species also keyed above).
                     11 Stigmas 2; achenes dorsiventrally compressed; spikelets subterete, elliptic in ×-section; [subgenus Juncellus, section Stoloniferi]
Click images to enlarge and show more photo credit.

Key to Cyperus, Key ZA: Key to Cyperus of various affinities -- Scales cuspidate to awned

Copy permalink to share | Check for keys that lead to this key

1 Leaves, bracts, and culms viscid (sticky); leaves involute; achenes (1.4-) 1.8-2.4 mm long, either with an elongate beak or a whitish overlay and spongy stipitate base; relatively robust plants, culms 1-7 dm tall; [subgenus Cyperus, section Elegantes]
  2 Scales 6-22, with stout, slightly excurved mucros 0.2-0.3 mm long at apex; achenes black to reddish-brown (1.4-) 1.8-2 mm long × 0.91 mm wide, broadly obovoid, surfaces with a whitish-gray overlay (sometimes sloughing off in age)
  2 Scales 10-20 (-40), with cusps 0.2-0.8 mm, usually narrow, awn-like and recurved at least in the upper scales; achenes brown, 2-2.4 mm long × 0.5-0.8 mm wide, narrowly obovoid
1 Plants not viscid; leaves flat or V-shaped; achenes 0.6-1.5 mm long, without a spongy stipe or whitish overlay, obtuse to apiculate, not beaked; mostly diminutive annuals.
    3 Scales divaricate at maturity, not or barely overlapping, with straight cusps; spikelets held erect-ascending in umbellate to oblong spikes; culms arising singly or slightly cespitose, either with indurate rhizomes to 4 cm or cormose culm bases; [subgenus Cyperus, section Laxiglumi]
      4 Scales 1.3-2.5 mm long, suborbicular, mucronulate (mucro excurrent ≤ 0.2 mm); spikes mostly globose or ovoid, spikelets usually spreading or radiating in all directions (erect-ascending in C. houghtonii); achenes broadly obovoid, ca. 1.5× as long as wide
      4 Scales 2.2-3.2 long, broadly ovate, cuspidate (midrib excurrent (0.3-)0.5-1mm on distal scales); achenes ellipsoid, ca. 2× as long as wide; plants rhizomatous, culms sharply trigonous.
    3 Scales appressed except for excurved cusp (straight in C. nipponicus and C. compressus); spikelets in globose to ovoid clusters or spikes; plants cespitose, annual (perennial in C. acuminatus).
        5 Longest inflorescence bract vertical, appearing as a continuation of the culm; scales with stout, excurved, mucronate apices at most 0.3 mm long; scales with 1 central keel, bicarinate in the basal 1/3, otherwise nerveless or with 2 obscure lateral ribs; [subgenus Pycnostachys, section Luzuloidei]
        5 Longest inflorescence bract ascending; scales with narrow, awnlike cusp (0.3-) 0.5-1 (-1.3) mm long; scales not bicarinate in the basal 1/3, conduplicate to broadly rounded, variously nerved.
          6 Achenes laterally flattened; scales with greenish midrib, otherwise hyaline, nerveless; cusp 0.3-0.5 mm long; stigmas 2; [rare introduction, FL]; [subgenus Pycreus]
          6 Achenes trigonous to moderately dorsiventrally compressed; scales weakly to strongly 3-13-nerved; cusp to 1 mm long; stigmas 3 (2 in C. nipponicus).
             7 Floral scales weakly 3-9-nerved, laterally greenish to whitish; scale tips with straight to slightly excurved cusp at most 0.7 mm long; achenes broadly obovoid (C. compressus) or oblong-obovoid, dorsiventrally compressed (C. nipponicus).
               8 Achenes broadly obovoid, sharply trigonous; spikelets strongly compressed-quadrangular; cusp 0.5-0.7 mm long, slightly excurved. [widespread]; [subgenus Cyperus, section Compressi]
               8 Achenes narrowly obovoid, planoconvex; spikelets subterete, elliptic in cross-section; cusp < 0.5 mm long, straight; [introduced, NJ, NY]; [subgenus Juncellus; section Pygmaei]
             7 Floral scales strongly (5-) 7-13-nerved nearly to the margins, or medially 3-ribbed, often orange to reddish brown laterally at maturity; scale tips with conspicuously excurved cusp 0.5-1 (-1.3) mm long; achenes narrowly ellipsoid to oblong, trigonous.
                 9 Scales 3-ribbed medially; spikelets in loose digitate clusters, the rachis essentially absent; achenes 0.5-0.6 mm long, coarsely papillose; [subgenus Pycnostachys]
                 9 Scales strongly (5-) 7-13-nerved nearly to margins; spikelets in dense ovoid spikes, rachis obscured by spikelets but well-developed; achenes 0.7-1.2 mm long, puncticulate or minutely papillose; [subgenus Cyperus, section Aristati].
                   10 Achenes 0.5-0.6 mm wide, < 2× as long as wide, cuneate to the base; scales 1.0-2.0 mm wide, 9-13-nerved; filaments ca. 2.5 mm long; anthers 0.4-0.8 mm long
                   10 Achenes (0.2-) 0.3-0.4 (-0.5) mm wide, > 2× as long as wide, with a minute stipe at the base; scales 0.5-1.0 mm wide, (5-) 7-9 (- 11)-nerved; filaments ca. 1.5 mm long; anthers 0.3-0.4 mm long
Click images to enlarge and show more photo credit.

Key to Cyperus, Key ZB: Key to Cyperus, subgenus Pycnostachys, section Luzuloidei -- Spikelets in glomerulate heads; scales with midrib bicarinate in basal 1/3, laterally nerveless or 2-ribbed.

Copy permalink to share | Check for keys that lead to this key

1 Culms sharply trigonous in cross-section (the faces concave), and harshly scabrid on the angles (very rarely smooth); leaf blades, sheaths and bracts nodulose, with cross-ribs between veins.
  2 Inflorescence congested, primary rays 3-5, secondary and tertiary rays absent; scales ovate, 1.4-1.6 mm long; spikelets 1.5-2.2 mm wide, in dense globose clusters; achenes 1.0-1.2 mm long, < 0.7× as long as the subtending floral scale
  2 Inflorescence broad, diffuse, primary rays 6-12, secondary and often tertiary rays present; scales oblancolate, (1.3-) 1.5-2.0 (-2.4) mm long, spikelets 2-3.2 mm wide, in hemispheric to irregularly globose clusters; achenes 1.2-1.5 mm long, at least 0.7× as long as the subtending floral scale
1 Culms obtusely trigonous in cross-section (faces usually convex), not scabrid on the angles, sometimes scabrous across faces; leaf blades and bracts not nodulose.
    3 Bracts 1-3, < 3 mm wide, the largest erect, appearing as a continuation of the culm; culms slender, 1-2 mm in diameter; plants cespitose, fibrous-rooted annuals (perennial in C. reflexus).
      4 Scales yellowish green or straw-colored, sometimes with an orange tinge, apices incurved to straight; stems and rays scabridulous with retrorse prickles, rough to the touch (rarely with only a few prickles); spikelet clusters mostly loosely and irregularly fasciculate.
      4 Scales either dark reddish-brown laterally, often with contrasting green keels or mucronate and conspicuously excurved apically; culms glabrous (rarely scabridulous in C. acuminatus); spikelet clusters densely globose to ovoid or pyramidal.
        5 Scales slightly to strongly excurved apically, mucronate, greenish or stramineous, or sometimes light orange-brown laterally, but this grading evenly into the greenish or yellowish medial portion; achenes papillose, broadly ellipsoid; plants annual, rhizomes absent; heads hemispheric to globose
        5 Scales slightly excurved to incurved apically, acute, deep reddish-brown laterally at maturity, abruptly greenish or yellowish on the keels; achenes rugulose or reticulate, ellipsoid to oblong; plants perennial, rhizomes present (inconspicuous); heads very densely ovoid to pyramidal
    3 Bracts (3-) 6-12, the larger > 3 mm wide, spreading to ascending; culms coarser, 2-5 mm in diameter; plants rhizomatous or cespitose perennials.
          6 Achene without basal thickening.
             7 Spikelets elliptic to orbiculate-ovate, ≤ 5 mm long, very densely packed in subglobose, lobulate heads; achenes linear, 4-5× as long as wide, falcate; scales oblong-spatulate, (1.5-) 2-2.5 mm long, apices often excurved
             7 Spikelets lanceolate to linear, usually > 5 mm long, heads usually looser; achenes narrowly to broadly ovoid or ellipsoid, not falcate, < 4× as long as wide; scales ovate to lanceolate, to 2 (-2.3) mm long, apices straight to incurved (excurved in C. eragrostis).
               8 Scales declined 60-90 degrees from the rachilla, blunt, incurved; achenes ellipsoid, < 3× as long as wide, narrowed to a distinct stipe; achene surfaces distinctly honeycomb-reticulate, often iridescent
               8 Scales declined 30-45 (-60) degrees from the rachilla; achenes very narrowly ellipsoid, 3-4× as long as wide, stipe absent to poorly developed (ellipsoid with distinct stipe in C. eragrostis); achene surfaces dull, smooth to puncticulate or obscurely reticulate.
                 9 Spikelets > 3 mm wide; scales 2-2.3 mm long, excurved apically; heads 20-40 mm in diameter, densely globose, lacking secondary rays; achenes broadly ellipsoid, < 2.5× as long as wide, with a distinct stipe
                 9 Spikelets < 3 mm wide; scales < 2 mm long, incurved to straight; heads mostly ≤ 20 mm in diameter, usually with secondary rays; achenes narrowly ovoid or ellipsoid, 3-4× as long as wide, stipe absent.
                   10 Culms smooth (or rarely with sparse retrorse prickles); plants robust perennials, with thick deeply set rhizomes; culms mostly >5 dm tall, bases purplish black; floral scales diverging about 30 degrees from the rachilla, pale green; heads usually tightly globose
                   10 Culms scabrid (at least apically) with abundant retrorse prickles; plants short-lived cespitose perennials, rhizomes absent; culms mostly < 5 dm tall, bases reddish or brownish; floral scales usually diverging at least 45 degrees from the rachilla, yellowish to yellowish-green; heads mostly loosely and irregularly fasciculate, with flattened spikelets fanned out like a deck of cards
Click images to enlarge and show more photo credit.

Key to Cyperus, Key ZC: Key to Cyperus, subgenus Pycnostachys, sections Fusci, Diffusi, and Haspani -- Spikelets in digitate clusters or glomerulate heads; scales broadly rounded or conduplicate

Copy permalink to share | Check for keys that lead to this key

1 Scales orbiculate or broadly obovate, to 1.1 mm long and wide, about as broad as long, minutely mucronate at the tip (“bead-like”); achenes 0.6-0.9 mm long × 0.3-0.4 mm wide, not much exceeded by the scales; plants fibrous-rooted annuals; [sect. Fusci]
  2 Heads very dense, spikelets 30-120 per head; scales 0.6-0.8 mm long × 0.6-0.8 mm wide, greenish; styles 0.1 mm long
  2 Heads looser, spikelets 3-12 per head; scales 0.9-1.1 mm long × 1 mm wide, light brown, bronze, whitish, or purplish brown; styles 0.3-0.4 mm long
1 Scales ovate to lanceolate, (1.1-) 1.6 mm long or longer, mucronate or not; achenes, if < 1.5 mm, much exceeded by (<1/2 the length of) the scales; plants perennial, often with cormose bases, stolons, or rhizomes.
    3 Leave involute; live plants viscid; scales with a mucronate to cuspidate apex at least 0.2 mm long, usually excurved; achenes with beaks 0.5-1.2 mm long or a whitish overlay and spongy stipitate base; [subgenus Cyperus, section Elegantes; keyed here as failsafes]
    3 Leaves flat or V-shaped; live plants not viscid; scales obtuse to acute (minutely mucronate in C. dentatus); achenes at most 1 mm long (longer in the obscurely spicate subg. Cyperus species keyed here as failsafes), without a beak or spongy stipitate base.
      4 Bracts large and conspicuous, 7-11, lanceolate, 5-25 mm wide, the main veins whitish-banded adaxially; inflorescence open and diffuse, often with 2nd and 3rd order rays; [cultivated, rarely naturalizing]; [section Diffusi]
      4 Bracts usually < 7, linear, < 10 mm wide, without whitish banding on the main veins, shorter than the culm.
        5 Spikelets in dense spikes, inflorescence often capitate; scales divaricate at maturity, rounded on the keel, weakly 5-13-nerved; achenes (1-) 1.4-2.5 mm long; plants mostly with hardened cormose culm bases, sometimes also rhizomatous; [dry, sandy habitats]; [subgenus Cyperus, section Laxiglumi; keyed here as failsafes].
        5 Spikelets in loose digitate clusters, rays elongate (except some forms of C. haspan); scales closely appressed, conduplicate and weakly 1-3 (-5)-ribbed; achenes 0.3-1 mm long; plants stoloniferous or rhizomatous; [mostly in wetlands]; [section Haspani]
          6 Leaf blades usually absent; bracts 2 (-4), usually much reduced; achenes 0.3-0.6 mm long, globose to obovoid.
             7 Rays 5-15; anther 1-1.2 mm long; culms hard, not much flattening in pressing; [native]
             7 Rays 200-300; anthers 0.3-0.5 mm long; culms soft, terete, flattening in pressing; [cultivated, rarely naturalizing]
          6 Leaf blades present; bracts 3-5, well-developed and often exceeding the inflorescence; achenes 0.7-1 mm long.
               8 Scales 2-2.5 mm long × 1.2-2 mm wide, ovate or broadly elliptic, 3-26 (-50) per spikelet, minutely mucronate, sometimes excurved; spikelets ovate to linear, straight, light brown to reddish-brown laterally with greenish midribs; plants with stolons terminated by tubers, and often proliferous spikelets
               8 Scales 2.5-3 mm long × 1-1.8 mm wide, relatively narrowly ovate-elliptic, 20-60 per spikelet, blunt and incurved; spikelets lanceolate to linear, often contorted, pale yellowish at maturity; plants with stolons, lacking tubers or proliferous spikelets
Click images to enlarge and show more photo credit.

Key to Cyperus, Key ZD: Key to Cyperus, subgenus Cyperus -- Spikelets quadrangular to subterete; scales 1-8, persistent rachillas deciduous, articulate at the base

Copy permalink to share | Check for keys that lead to this key

(c) Montes de Oca, Joseph - CC-BY-NC, permission granted to NCBG
(c) Bradley, Keith
1 Culms, rays, and leaves bluish-glaucous, papillose; leaves harshly scabrid on margins and midrib; spikes with numerous well-developed branches or secondary rays; spikelets dark reddish brown at maturity
1 Culms, rays, and leaves green, not papillose; leaves glabrous to scabridulous; spikes solitary or with a few reduced basal branches; spikelets various.
(c) Fleming, Gary P.
  2 All but the uppermost spikelets strongly (-weakly in some forms of C. hystricinus) reflexed; scales (3.8-) 4-4.9 (-5.4) mm long, terminal involute and prolonged distally, midrib often bent downward; achenes linear to linear-oblong, (2.2-) 2.5-3 (-2.3) mm long; [section Umbellati, subsection Longistylis, C. retrofractus complex]
    3 Spikes mostly at least 2× as long as wide, slightly (or not) narrowed to base, spikelets reflexed to spreading; culms, leaves, and bracts glabrous except for marginal prickles on leaves and bracts; rachilla wing clasping achene for its entire length (concealing it in abaxial view); floral scales golden-brown when mature
    3 Spikes mostly about as long as wide and strongly narrowed to the base, spikelets reflexed; culms scabrous, bracts scabridulous and also often hirtellous; rachilla wing clasping achene for <3/4 its length; floral scales greenish to brown or reddish-purple-striped.
      4 Rays scabrid throughout their lengths; leaves and bracts puberulent; longest ray equal to or longer than the longest bract; culms roundly trigonous to subterete; terminal scale spinose distally; scales 1-2 (-3); spikes tight, burlike, turbinate
      4 Rays glabrous or rarely with a few hairs just below the spike; leaves and bracts with hairs confined to abaxial midrib; longest ray shorter than longest bract; culm sharply trigonous; terminal scale involute but not spinose; scales (2-)3-6; spikes often loose, sometimes more elongate
(c) Campos, Aidan
(c) Fleming, Gary P.
  2 Spikelets ascending to spreading, or reflexed in the lower half of spike; scales 1.8-5.3 mm long, terminal scale not modified as above; achenes ellipsoid to narrowly oblong, 1.2-2.4 (-2.6) mm long (linear-oblong in C. refractus).
(c) Mesaglio, Thomas - CC-BY
        5 Spikes densely cylindric, all sessile or 1-3 (-5) lateral spikes on short horizontal rays; spikelets ellipsoid (rarely oblong-ellipsoid), with 1-2 (-4) scales; [section Umbellati, subsection Brevistyli].
          6 Spikes dense, the rachis obscured when pressed; achenes lacking a stipitate base, apiculate at the apex; [native of Mexico and Central America, introduced northward along the Gulf and Atlantic coasts]
          6 Spikes relatively loose, the rachis usually visible when pressed; achenes cuneate to a stipitate base, broadly rounded to acute at the apex; [native, s. TX, uncertain reports]
(c) Fleming, Gary P.
        5 Spikes oblong to ovoid (cylindric in C. tetragonus), primarily on well-developed rays; spikelets oblong-lanceoloid to linear, with (1-) 2-8 scales.
             7 Spikelets very closely spaced, obscuring the rachis in life and when pressed; [section Umbellati, subsection Brevistylis]
               8 Spikes broadly and appearing (because of longer spikelets) relatively loosely ellipsoid to ovoid-cylindric, 2.5-7 cm long × 1.5-6 cm wide; spikelets (11-) 12-25 (-28) mm long; achenes 2.2-3 mm long (if < 2.5 mm long, noticeably falcate).
                 9 Spikes dense, ellipsoid to obovoid, convex, with 50-90 spikelets; scales 3-6 (-7), each 4-4.6 mm long, not red-purple striate; achenes 3-4× as long as wide, falcate
                 9 Spikes loose, broadly ovoid or ellipsoid to ovoid-cylindric, with 13-75 spikelets; scales 4-8(-11), each 4.5-5.3 mm long, red-purple striate; achenes 4-5× as long as wide, straight
               8 Spikes tightly globose or to oblong, not more than 2.5 cm long or 2 cm wide; spikelets 2-8 mm long; achenes < 2.3 mm long, straight.
(c) Ward, Scott G
(c) Fleming, Gary P.
                   10 Spikes uniformly convex throughout, globose or globose-ellipsoid, so dense as to appear nearly smooth in silhouette; scales 3.5-4.6 (-4.8) mm long, acute
(c) Bradley, Keith
                   10 Spikes cylindric, oblong, ellipsoid, or ovoid, mostly less dense; scales 1.8-3.6 mm long (or, if longer, mucronate).
                     11 Terminal scale of spikelet reduced, sterile, involute, with a minute but distinct mucro to 0.3 mm long, usually uncinate (hooked); fertile scales (if more than one) not overlapping on the same side of the rachilla, usually red-brown or orangeish laterally at maturity; leaf blades 1-3 mm wide; [Cyperus retroflexus complex]
                       12 Fertile floral scales 1.9-3.0 (-3.3) mm long; rachilla wing usually membranaceous throughout; rachilla lacking lateral nerves; longest spikelets 2.8-5.8 (-8.0) mm long; terminal sterile floral scale of spikelet often much reduced, less than 2/3 the length of fertile floral scales; longest peduncle less than 2.7 (-3.9) cm long; plants diminutive, culms 3-35 (-45) cm tall
                       12 Fertile floral scales (2.8-) 3.0-3.9 mm long; rachilla wing usually chartaceous beyond clasped achene angle, border membranaceous; rachilla with two lateral nerves, one along each side of the median; longest spikelets 4.9-9.0 (-11.3) mm long; terminal sterile floral scale usually not greatly reduced, 2/3 or more the length of fertile floral scales; longest peduncle (0.5-) 2.4-6.8 cm long; plants more robust, culms usually >25 cm tall
                     11 Terminal scale of spikelet not differentiated; scales acute, greenish-hyaline to brownish or straw-colored laterally; scales overlapping; leaf blades 1.5-5 mm wide.
                          13 Spikes relatively loosely ovoid, 8-20 mm wide, with (5-) 10-50 (-70) spikelets, lacking basal branches; spikelets (2.2-) 3.5-10 mm long, angular in ×-section, greenish-hyaline to pale yellow-green; bracts horizontal
                          13 Spikes densely oblong-ellipsoid to ovoid, 6-8 (-10) mm wide, with (13-) 30-200 (-274) spikelets, occasionally with short basal branches; spikelets 2.2-4 (-4.5) mm, subterete, straw-colored to brown at maturity; bracts horizontal or ascending to erect; [Cyperus retrorsus complex]
                            14 Achenes oblong-fusiform, stipitate, narrowed to both ends; spikes densely oblong to oblong-cylindric, often 3× or more as long as wide; scales ascending (the tips free), usually straw-colored; bracts horizontal
                            14 Achenes oblong, usually abruptly constricted at the ends; spikes ovoid to oblong, to 2× as long as wide (rarely longer in C. retrorsus); scales appressed, usually reddish-brown at maturity; bracts ascending to erect (sometimes horizontal in C. nashii).
                              15 Spikes > 1.5× as long as wide, each with (42-) 50-200 (-274) spikelets; achenes 0.4-0.5 (-0.6) mm wide; stems moderately cespitose; [widespread and weedy]
                              15 Spikes < 1.5 × as long as wide, each with (13-) 30-92 spikelets; achenes 0.5-0.7 mm wide; stems single to slightly cespitose; [Florida scrub, northward and westward in coastal dunes]
                                16 Rays 3-6 (-8); anthers 0.2-0.5 (-0.7) mm long; achenes 1.3-1.6 mm long × 0.5-0.6 mm wide
             7 Spikelet attachments spaced apart at least proximally, rachis not obscured when pressed and usually also visible in life.
                                  17 Fertile floral scales 1-3 (-5), not overlapping on the same side of the spikelet (if more than one); terminal scale reduced, sterile and involute, mucro usually uncinate; achenes (1.7-) 1.9-2.6 mm long; [section Umbellati, Cyperus retroflexus complex]
                                    18 Longest spikelets 10-21 mm long, strongly contorted; distal scales with scabrid midrib and mucro 0.6-1.9 mm long; longest floral scale of spikelet (3.5-) 3.7-4.8 mm long; anthers 0.5-1.3 mm long; achenes > 3× as long as wide; [TX]
                                    18 Longest spikelets usually < 10 mm long, at most somewhat flexuous with curved tips; distal scales with glabrous midrib and mucro 0.1-0.3 (-0.5) mm long; longest floral scale of spikelet (2.1-) 2.5-3.5 (-4.0) mm long; anthers 0.3-0.5 (-0.6) mm long; achenes 2-3 (-3.3)× as long as wide; [more widespread]
                                  17 Fertile floral scales 3-8, reaching the next scale or overlapping on the same side of the spikelet; terminal scale not involute and sterile, mucro straight; achenes various.
                                         20 Spikelets ±terete; scales 4.5-5.3 mm long, persistent, laterally reddish brown or tinted with reddish brown if paler and stramineous; achenes usually at least half as long as floral scale; achenes linear-oblong, 2.6-3 mm long, 5-6× as long as wide, > 0.5 mm wide; anthers 1-1.5 mm long; spikes usually broadly and convexly ellipsoid or ovoid, usually unbranched (or rarely with 1-2 reduced proximal branches); [section Umbellati, subsection Brevistylis]
                                         20 Spikelets flattened; scales 3.2-4.5 (-6) mm long, laterally golden yellow to stramineous; achenes less than half as long as floral scale; achenes oblong, (1.5-) 1.8-2.4 mm long, 3-4× as long as wide, < 0.4 mm wide; anthers 0.3-0.5 mm long; spikes usually parallel-sided, ovoid-cylindric, frequently branched; [section Strigosi]
                                           21 Plants perennial, ≥ 3 dm tall; culm 1.8-3 mm in diameter; floral scales not aristate
                                       19 Scales (2-) 2.5-3.2 (-4) mm long, acute to cuspidate; spikes narrowly cylindric to ovoid, spikelets mostly 4-8mm long (if longer, scales mucronate); achenes ellipsoid, 2-3× as long as wide; culm bases not cormose.
                                               23 Spikelets oblong to linear, 4-10× as long as wide; achenes ellipsoid to narrowly oblong; spikes narrowly to broadly cylindric to oblong or ellipsoid, ≥ 12 mm wide (C. retroflexus occasionally as narrow as 8 mm wide, but not cylindric).
                                                 24 Floral scales pale olivaceous to yellowish, not mucronate (rarely with a mucro to 0.1 mm long); spikes cylindric, loose, 6-10 spikelets per 5 mm span of the rachis; culms 0.5-1 mm in diameter; leaves 0.8-2.3 (-3) mm wide; [more widespread]; [section Tetragoni]
                                                 24 Floral scales straw-colored to reddish-brown, acute or mucronate, mucro up to 0.2 mm long; spikes loosely to densely ovoid to oblong, spikelets 8-21 per 5 mm span of the rachis; culms 1-2.6 mm in diameter; leaves (1-) 3-6 (-10) mm wide; [TX].
                                                    25 Floral scales not mucronate; spikes mostly narrowly oblong (usually 2× or more as long as wide); rachis, spikelets, bracteoles, peduncles, and prophylls not reddish brown striate or maculate (at 10× magnification); [section Tetragoni]
                                                    25 Floral scales mucronate, mucro at least 0.2 mm long; spikes densely ovoid to loosely ellipsoid-oblong (to 1.5× as long as wide); rachis, spikelets, bracteoles, peduncles, and prophylls usually conspicuously reddish brown striate or maculate (at 10× magnification); [section Strigosi].
                                                      26 Spikes denser, spikelets 11-21 per 5 mm span of the rachis (at least in the upper portion), often the upper spikelets ascending; scale color bilaterally variable, reddish or reddish-brown to whitish; spikelets estipitate or stipe to 0.2 mm long; spikes ellipsoid to oblong
Click images to enlarge and show more photo credit.

Key to Cyperus, Key ZE: Key to Cyperus, subgenus Cyperus of various affinities -- Spikelets compressed; scales deciduous or persistent; rachilla persistent or deciduous after the scales

Copy permalink to share | Check for keys that lead to this key

1 Culms and leaves bluish-glaucous in life; scales overlapping, slightly spreading, glossy reddish brown at maturity; plants cespitose perennials; [FL; beaches, dunes, coastal rock]
  2 Rays absent, inflorescence a single globose spike, rachis only 1-3 mm long; scales 1.5-2.2 mm long; achenes 1-1.2 mm long, glabrous, puncticulate, or papillose; leaves and bracts 1-2.5 mm wide; culms 0.5-1 mm in diameter; [section Laxiglumi]
  2 Rays present, inflorescence of multiple well-developed spikes, though often very congested; scales 2.5-3 mm long; achenes 1.3-2 mm long, coarsely punctate; leaves and bracts (1.5-) 3-10 mm wide; culms 0.8-2.6 mm in diameter; [section Thunbergiani]
1 Culms and leaves green, not glaucous; scales divaricate to closely imbricate, mostly greenish, light brown, or straw-colored (except C. rotundus and C. setigerus); [more widespread].
    3 Rachilla wingless (except C. prolixus and C. grayi); spikelets at maturity 2-4 mm wide, scales divaricate (the spikelet appearing coarsely serrate in outline).
      4 Rachis hispidulous; spikes loosely oblong-ovoid, with spikelets spreading, the elongate, well-developed rachis clearly visible; scales 1.8-2 mm long, light brown to yellowish; achenes 1-1.2 mm long; [sect. Proceri]
      4 Rachis glabrous; spikes densely ovoid or globose, or umbellate to oblong, the rachis elongate to nearly absent; scales 1.8-3.2 mm long; achenes 1.5-2.4 mm long (1-1.2 mm long in C. cephalanthus).
        5 Rays compressed; plants robust, up to 2m tall; inflorescence diffuse, 2nd-order rays present, erect, 1-10 cm long, usually bearing well-developed 3d-order rays 0.5-5 cm long; [sect. Distantes]
        5 Rays terete to trigonous; plants mostly less robust, to 1m tall; inflorescence more compact, 2nd- and 3rd-order rays absent or poorly developed.
          6 Plants robust, culms 40-100 cm tall, sharply trigonous, scabrid to hirtellate on the angles; spikes very densely ovoid, with 25-50+ spikelets, subtended by well-developed secondary bracts and often branched at the base; achenes 1.0-1.2 mm long, ellipsoid, <1/2 as long as the scales; [coastal prairies; LA, TX]; [sect. Thunbergiani]
          6 Plants smaller, culms to 50 cm tall, terete to trigonous, not scabrid (except C. schweinitzii); spikes relatively loose, with 3-24 spikelets, unbranched and lacking secondary bracts; achenes 1.5-2.2 mm long, mostly ≥ 1/2 as long as the scales; [dry, sandy or rocky soils; collectively widespread]; [sect. Laxiglumi].
             7 Inflorescence bracts deflexed (to horizontal); spikelets in a single sessile hemispheric to globose capitate cluster, or with an additional 1-4 smaller pedunculate spikes, these densely globose with an obscure rachis < 6 mm long; [Cyperus lupulinus complex]
               8 Anthers 0.8-1 mm long; achenes 0.5-0.8 mm wide, narrowly oblong; scales usually yellowish to yellowish brown; leaves very narrow, 0.5-2 mm wide
               8 Anthers 0.3-0.6 mm long; achenes 0.8-1.2 mm wide, ±ellipsoid; scales usually off-white to pale tan to light reddish brown; leaves often broader, 1-4 mm wide.
                 9 Scales 2.5-3.8 mm long, usually fitting loosely over the mature achene, the margins spreading or loosely clasping it; spikelet with 5-22 scales
                 9 Scales 1.8-2.5 mm long, usually fitting tightly over the achene, the margins tightly clasping it; spikelets with 3-7 scales
             7 Inflorescence bracts horizontal to erect; spikes primarily pedunculate, loosely globose, densely ovoid, or more elongate.
                   10 Scales 2.2-3.2 mm long with a conspicuous cusp > 0.3 mm long (at least on the distal scales); body of scale 2.2-3.2 mm long; spikes umbellate to oblong, spikelets all erect-ascending; achenes 2-2.4 mm long, ellipsoid; plants rhizomatous, culms sharply trigonous
                   10 Scales 1.3-2.5 mm long, acute or minutely mucronate (mucro ≤ 0.2mm long); spikes mostly globose or ovoid, spikelets usually spreading or radiating in all directions (erect-ascending in C. houghtonii); achenes 1.5-2.4 mm long; plants various.
                     11 Spikelets mostly erect-ascending, the spikes umbellate to broadly ovoid; scales with distinct mucro 0.1-0.2 mm long; achenes 1-1.5 mm wide, broadly ellipsoid; anthers 0.5-0.7 mm long
                     11 Spikelets radiating in all directions, the spikes globose or subglobose; scales acute; achenes 0.7-1.2 mm wide, narrowly ellipsoid or oblong-ellipsoid; anthers 0.7-1.2 mm long.
                       12 Rachilla winged, wings 0.6 mm wide; achenes 1.5-2 mm long × 0.7-1 mm wide; scales 2-2.8 mm long; anthers 0.7-1 mm long; [Atlantic coast, south to AL]
                       12 Rachilla wingless; achenes 2-2.4 mm long × 0.9-1.2 mm wide; scales 2.5-3 mm long; anthers 1-1.2 mm long; [Midwest south to LA]
    3 Rachilla winged, wings at least 0.4 mm wide; spikelets at most 2.2 mm wide, scales overlapping, tips closely imbricate, the margin appearing smooth or slightly serrate (some forms of C. strigosus have looser scales).
                          13 Scales 1-1.5 mm long, deciduous; spikes cylindric, with (20-) 40-80+ spikelets, often with secondary rays; fibrous-rooted annuals, but often robust, roots reddish; [sect. Fastigiati]
                            14 Plants with cormose culm bases; scales 3.2-4.5 (-6) mm, 3-11 per spikelet, pale greenish-brown to straw-colored, dull; spikelets strongly compressed (at maturity), the scales loosely overlapping, tips spreading; achenes narrowly oblong, (1.5-) 1.8-2.4 mm long; [section Strigosi]
                            14 Plants lacking cormose culm bases; scales 1.8-4 (-4.4) mm long, 6-36 (-42) per spikelet, various; spikelets often only slightly compressed, scales closely imbricate, tips appressed; achenes ellipsoid to oblong, 1.1-2 mm long.
                              15 Scales pale greenish-white, deciduous, usually with dark-speckled margins visible as a prominent dark line on each side of the spikelet; plants fibrous-rooted; anthers 0.6mm long, styles 0.6-1.2 mm long, stigmas 1-1.4 (-1.7) mm long; [rare introduction, FL]; [section Subimbricati]
                              15 Scales pale yellowish to brown or deep purple, persistent or deciduous; plants with well-developed rhizomes or stolons; anthers 1-2.5 mm long, styles (0.7-) 1-3.6 mm long, stigmas (1.2-) 1.8-6 mm long; [collectively widespread]; [section Cyperus].
                                16 Culms terete at least towards the base, nodose-septate, with internal partitions every 5-50 mm, more frequent upwards; leaves usually all reduced to bladeless sheaths; bracts 2 (-4), erect, reduced, mostly < 2 cm long
                                  17 Scales deciduous, (2.2-) 2.7-4.5 (-6) mm, mostly reddish-brown; robust perennials 5-10dm tall from thick, indurate rhizomes, lacking tubers; achenes maturing, oblong
                                  17 Scales persistent, 1.8-3.4 mm long, mostly yellowish or dark glossy purplish; plants mostly 1-6 dm tall (rarely taller in C. esculentus), with slender stolons 1-2 mm in diameter, these producing terminal tubers; achenes ellipsoid or not maturing.
                                    18 Spikelets (2-) 3-14 per spike, bracts often not exceeding the inflorescence; scales glossy dark purplish, with green keels and hyaline border; culm bases indurate, stolons wiry, horizontal, 1-2 mm in diameter, producing irregular, often elongate tubers
                                    18 Spikelets (3-) 10-28 per spike, bracts exceeding the inflorescence; scales yellowish to dull reddish-brown; culm bases not indurate, stolons spongy, weak, 1 mm in diameter, producing globose tubers; [Cyperus esculentus complex].