Flora of the Southeastern United States
2022 Edition

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Key to Cyperaceae

1 Achene enclosed in a perigynium (a sac-like structure); [subfamily Caricoideae, tribe Cariceae]
1 Achene not enclosed in a perigynium.
..2 Scales obviously and strongly distichously imbricate; spikelets either aggregated into spikes or heads (Cyperus, Dulichium, Schoenus), or solitary (Abildgaardia); [subfamily Cyperoideae].
....3 Spikelets solitary and terminal; of FL peninsula in our area]
....3 Spikelets aggregated into terminal or axillary spikes or heads; [widespread in our area].
......4 Inflorescence axillary; leaves predominantly cauline, conspicuously 3-ranked; perianth bristles subtending the achene 6-9; [tribe Dulichieae]
......4 Inflorescence terminal, more-or-less scapose (though immediately subtended by leafy bracts); leaves predominantly basal, not 3-ranked; perianth bristles absent (Cyperus) or present (Schoenus); [tribe Cypereae].
........5 Perianth bristles present
........5 Perianth bristles absent
..2 Scales spirally imbricate; spikelets not usually aggregated.
..........6 Achene (when ripe) bony and white; style base persistent on the summit of the achene, forming a differently-textured or differently-colored tubercle; spikelets all unisexual, the pistillate spikelets 1-flowered, the staminate spikelets several-flowered; [subfamily Sclerioideae, tribe Sclerieae]
..........6 Achene mostly brown, black, or tan; style base either persistent as a differentiated tubercle (Bulbostylis, Eleocharis, Rhynchospora) or not (Cladium, Eriophorum, Fuirena, Isolepis, Cyperus, Schoenoplectus, Scirpus, Trichophorum); spikelets mostly or all bisexual; [subfamily Cyperoideae].
............ 7 Style base persistent as a differentiated tubercle (this small and inconspicuous in Bulbostylis and some spp. of Rhynchospora).
............ ..8 Leaves consisting of bladeless sheaths; spikelet 1 per stem, terminal (very rarely proliferating and with > 1 spikelet); [tribe Eleocharideae]
............ ..8 Leaves with well-developed blades; spikelets few to many per stem, usually subtended by foliaceous bracts.
............ ....9 Perianth bristles absent; spikelets several-many-flowered; leaves capillary; [tribe Abildgaardieae]
............ ....9 Perianth bristles present (rarely absent in species without capillary leaves); spikelets 1-2-flowered (several-many-flowered in some species without capillary leaves); leaves capillary to broad; [tribe Schoeneae]
............ 7 Style base not persistent as a differentiated tubercle.
............ ......10 Achene not subtended by a modified perianth of bristles or scales (in addition to the scales of the spikelets).
............ ........11 Involucral bracts 1-3, the lowest erect, appearing like a continuation of the culm, the inflorescence therefore appearing lateral.
............ ..........12 Achenes 0.5-0.7 mm long, 1.8-3× as long as wide, minutely papillose in longitudinal lines; [tribe Cypereae]
............ ..........12 Achenes 1.2-1.5 mm long, 1-1.4× as long as wide, minutely pitted or transversely rugose.
............ ............ 13 Achenes transversely rugose; [tribe Fuireneae]
............ ............ 13 Achenes minutely pitted in longitudinal lines; [tribe Cypereae]
............ ............ ..14 Spikelets in a loose cluster (not spherical)
............ ............ ..14 Spikelets aggregated into spherical glomerules
............ ........11 Involucral bracts 2-several, spreading, the inflorescence therefore appearing terminal.
............ ............ ....15 Plants diminutive, to 5 dm tall; leaves 3-15 cm long, to 1 mm wide; [tribe Abildgaardieae]
............ ............ ....15 Plants moderate to very robust, 7-30 dm tall; leaves 30-150 cm long, 1.5-15 mm wide.
............ ............ ......16 Flowers 1-2 per spikelet; [tribe Schoeneae]
............ ............ ......16 Flowers several-many per spikelet.
............ ............ ........17 Style fimbriate; leaves 0.5-5 mm wide; [tribe Abildgaardieae]
............ ............ ........17 Style smooth; leaves (2-) 5-18 mm wide; [tribe Scirpeae]
............ ......10 Achene subtended by a modified perianth of either bristles, 3 stalked paddle-like scales, or 1-2 broad-based scales (in addition to the scales of the spikelets).
............ ............ ..........18 Achene subtended by stalked paddle-like scales or broad-based scales.
............ ............ ............ 19 Achene lacking a perianth, but subtended by 1-2 broad-based scales; plants 0.5-3 dm tall; [tribe Cypereae]
............ ............ ............ 19 Achene subtended by a perianth of 3 stalked paddle-like scales; plants 2-7 dm tall; [tribe Fuireneae]
............ ............ ..........18 Achene subtended by bristles.
............ ............ ............ ..20 Bristles 10-many, > 5× as long as the achene, white to tawny, straight; [tribe Scirpeae]
............ ............ ............ ..20 Bristles 1-6, usually < 4× as long as the achene, brown, straight or conspicuously twisted (twisted if > 3× as long as the achene).
............ ............ ............ ....21 Involucral bracts lacking, or consisting only of the slightly modified basal scales of the solitary and terminal spikelet; [of hillsides, upland forests, or cliffs; never (in our area) in marshes, bogs, or streambeds]; [tribe Scirpeae]
............ ............ ............ ....21 Involucral bracts present, consisting either of a single, erect bract appearing as a continuation of the culm (the inflorescence thus appearing lateral) or of 2 or more spreading, foliaceous bracts (the inflorescence thus appearing terminal); [of marshes, bogs, streambeds, ditches, or (rarely) terrestrial or on rock outcrops].
............ ............ ............ ......22 Main involucral bract 1 (rarely 2), erect, appearing as a continuation of the culm (the inflorescence thus appearing lateral, though in some species the longer inflorescence branches may overtop the bract); [tribe Fuireneae]
............ ............ ............ ........23 Achenes rugulose; plants annual
............ ............ ............ ........23 Achenes smooth; plants perennial
............ ............ ............ ......22 Main involucral bracts 2-8, spreading and foliaceous (the inflorescence thus appearing terminal).
............ ............ ............ ..........24 Spikelets 10-40 mm long, 6-12 mm in diameter, 3-50 per culm; [tribe Fuireneae]
............ ............ ............ ..........24 Spikelets 2.5-19 mm long, 2-4 mm in diameter, usually > 50 per culm; [tribe Scirpeae]