Flora of the Southeastern United States
2022 Edition

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Key to Poaceae, Key M: grasses with 2+ florets, these exceeded and usually concealed by the glumes

1 Spikelets disarticulating below the glumes, the spikelets falling as a whole or in clusters; [tribe Poeae]
1 Spikelets disarticulating above the glumes, the glumes remaining attached to the pedicel.
..2 Spikelets dimorphic, paired, each pair consisting of a lower spikelet with sterile florets and an upper spikelet one with fertile florets; [tribe Poeae]
..2 Spikelets monomorphic.
....3 Spikelets each with 1 fertile (bisexual) floret, with 1-several sterile florets, either towards the base or towards the tip of the spikelet.
......4 Fertile floret basal, with 1-several sterile florets towards the tip of the spikelet; [tribe Cynodonteae; subtribe “incertae sedis”]
......4 Fertile floret terminal, with 1-several sterile florets towards the base of the spikelet (the sterile florets sometimes knoblike or like tufts of hairs, and not obviously like florets); [tribe Poeae].
........5 Spikelets with 2 florets, the lower floret staminate and of similar size as the upper, pistillate or bisexual floret; lemma of the lower floret awned; lemma of the upper floret unawned or awned
........5 Spikelets with 2-3 florets, the lower 1-2 florets staminate or sterile, either highly reduced to knobs or tufts of hairs, or shorter than to longer than the terminal, bisexual floret; lemma of the lower florets either awned or unawned; lemma of the upper floret unawned.
..........6 Lower sterile florets 2, shorter than to exceeding the bisexual floret; fresh leaves with sweet vanilla odor when crushed; lemma of the lower florets awned or unawned
............ 7 Glumes unequal, the lower shorter than the upper; lowest 2 florets sterile.
............ 7 Glumes subequal; lowest 2 florets staminate.
..........6 Lower sterile florets 1-2, either highly reduced to knobs or tufts of hairs, or consisting of linear to lanceolate lemmas up to ¾ as long as the bisexual floret; all lemmas unawned
....3 Spikelets each with 2 or more fertile florets.
............ ..8 Spikelets 18-50 mm long; glumes 9-11-veined; [tribe Poeae]
............ ..8 Spikelets 2.5-20 mm long; glumes 1-7-veined.
............ ....9 Lemma awns apical or dorsal (arising from the apex of the lemma or from the back of the lemma in its upper half).
............ ......10 Spikelets 7-20 mm long, with 3-12 florets; ligule of hairs; lemma awn 5-15 mm long; [collectively widespread in our area]; [tribe Danthoniae]
............ ......10 Spikelets 5-7.5 mm long, with 2 (-3) florets; ligule membranous, 0.5-4 mm long; lemma awn 3-8 mm long; [rare disjunct on a few high elevation peaks, disjunct from the north]; [tribe Poeae]
............ ....9 Lemma awns basal (arising from the lower half of the lemma); [tribe Poeae].
............ ........11 Rachilla glabrous, not prolonged beyond the upper floret; spikelets 1.7-3.8 mm long
............ ........11 Rachilla hairy, prolonged beyond the upper floret as a bristle; spikelets 2.5-7 mm long
............ ..........12 Lemma awn 4-8 mm long, geniculate, exserted beyond the tips of the glumes; lemmas minutely scabrous, dull; leaf blades involute, appearing filiform (rounded in cross-section); ligule 0.5-3 (-5) mm long
............ ..........12 Lemma awn 2-3 mm long, straight or nearly so, scarcely (or not at all) exserted beyond the tips of the glumes; lemmas smooth, shiny; leaf blades flat or folded at the midvein (V-shaped in cross-section); ligule 3-10 (-17) mm long