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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 |
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] |
............ ............ 13 Scales 1.8-4.5 (-6) mm, deciduous or persistent; spikes ovoid, with (2-) 3-50 spikelets; stoloniferous, rhizomatous, cormose-based, or ( C. sphacelatus) cespitose perennials. |
............ ............ ..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 |
............ ............ ......16 Culms trigonous to rounded-trigonous, not nodose-septate; leaf blades present; bracts (2-) 3-8, spreading to ascending, well-developed. |
............ ............ ........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]. |
............ ............ ............ 19 Spikelets ascending-erect; floral scales deltate-ovate, widest 1/4-1/3 of the way from the base |
............ ............ ............ 19 Spikelets spreading; floral scales ovate to ovate-lanceolate, widest near the middle. |
............ ............ ............ ..20 Style and stigma combined < 4.2mm long; floral scales 1.8-2.7 mm long; anthers (1-) ca. 1.3 (-1.6) mm long |
............ ............ ............ ..20 Style and stigma combined > 4.2mm long; floral scales (2.7-) 2.9-3.4 mm long; anthers (1.2-) 1.3-2.1 mm long |