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1 Leaves ovate-lanceolate, 2-10 cm long, 2.5-7× as long as wide; plants weak-stemmed annuals, branching, decumbent, rooting at the lower nodes; [exotic weeds]. |
..2 Leaves cordate-clasping at base; spikelets not paired, unaccompanied by a vestige |
..2 Leaves tapering to a broadly cuneate base; spikelets paired (one of the pair sometimes vestigial) |
1 Leaves lanceolate to linear, either longer or proportionately narrower; plants either perennial or coarse annuals with erect and mostly unbranched culms. |
....3 Spikelets embedded in the thickened rachis (the inflorescence thus like an ear of corn), or fitting into grooves in the thickened rachis (the inflorescence thus cylindrical and resembling a rat's tail), or the pistillate inflorescences enclosed in a hard, bead-like, pearly-white, modified bract. |
......4 Spikelets unisexual, with male and female spikelets in separate inflorescences or in different parts of the same inflorescence. |
........5 Internode narrower than and more-or-less enclosed by the female spikelet |
........5 Internode broader than and more-or-less enclosing the female spikelet. |
..........6 Racemes of mixed sex, female flowers below, and male above |
..........6 Racemes of single sex, the female inflorescences (“ears”) borne on axillary branches, the male inflorescences (“tassels”) terminal on the culm |
......4 Spikelets, or at least one of each pair, bisexual. |
............ 7 Culms 2-45 cm tall; leaves 1-5 mm wide; plants perennial, obviously and prominently rhizomatous; lower glume with pectinate margins; [commonly naturalized turf grass and roadside weed] |
............ 7 Culms 30-400 cm tall; leaves 2-25 mm wide; plants annual or perennial, cespitose or short-rhizomatous; lower glume winged or not, but not pectinate. |
............ ..8 Lower glumes of the sessile spikelets rough, rugose, pitted, tuberculate or alveolate between the keels |
............ ..8 Lower glumes of the sessile spikelets smooth or scabrous. |
............ ....9 Pedicels at least partially fused to the rame axes |
............ ....9 Pedicels appressed, but not fused, to the rame axes |
............ ......10 Pedicellate spikelets 4-8 mm long |
............ ......10 Pedicellate spikelets 1-3 mm long |
....3 Spikelets not embedded or fitting into grooves in the rachis, the rachis slender (the spikelets visibly separate and often pedicelled). |
............ ........11 Pedicelled spikelet similar to the sessile spikelet, both fertile. |
............ ..........12 Spikelets falling separately from the persistent rachis. |
............ ............ 13 Panicle contracted, spikelike; glumes membranous |
............ ............ 13 Panicle loose; glumes cartilaginous or coriaceous |
............ ..........12 Spikelets falling in pairs together with sections of the disarticulating rachis. |
............ ............ ..14 Spikelets awned with awns 10-26 mm long; anthers 2; [native, collectively common and widespread] |
............ ............ ..14 Spikelets unawned or with awns to 5.2 mm long; anthers 3; [exotic, rarely encountered] |
............ ............ ....15 Spikelets unawned |
............ ............ ....15 Spikelets with awns 4-5.2 mm long |
............ ........11 Pedicelled spikelet differing from the sessile in shape and sex (sometimes represented only by a pedicel). |
............ ............ ......16 Spikelets awned, the awn 10-20 cm long. |
............ ............ ........17 First glume lacking glands; panicle open, the branches 5-8 cm long |
............ ............ ........17 First glume with a row of punctate, concave glands; panicle contracted, spikelike |
............ ............ ......16 Spikelets with or without awns, if awned the awns < 5 cm long. |
............ ............ ..........18 Inflorescence a panicle, the branches not subtended by sheaths. |
............ ............ ............ 19 Pedicelled spikelet represented by pedicel only; apex of sheath bearing 2 auricles 1-10 mm long; [native] |
............ ............ ............ 19 Pedicelled spikelet present, staminate; apex of sheath truncate; [exotic] |
............ ............ ..........18 Inflorescence of 1-13 digitate (whorled) racemes borne at the summit of a peduncle, the peduncle subtended by a raceme sheath. |
............ ............ ............ ..20 Racemes 1 per peduncle and raceme sheath |
............ ............ ............ ..20 Racemes 2-13 per peduncle and raceme sheath. |
............ ............ ............ ....21 Pedicels of the pedicelled (reduced or absent) spikelets terete or slightly flattened and grooved on one side only |
............ ............ ............ ....21 Pedicels of the pedicelled (reduced or absent) spikelets strongly flattened and with or without grooves on both sides. |
............ ............ ............ ......22 Rame internodes and pedicels with a translucent medial groove; pedicelled spikelets smaller than the sessile spikelets (or vestigial/absent) |
............ ............ ............ ......22 Rame internodes and pedicels without a translucent medial groove; pedicelled spikelets ca. the same size as sessile spikelets |