Flora of the Southeastern United States
2022 Edition

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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.

Key to Bromus

1 Lemmas compressed and strongly keeled (the whole spikelet thus strongly laterally flattened); first glume 3-9-nerved; [section Ceratochloa]
1 Lemmas rounded or weakly keeled (the whole spikelet therefore terete to somewhat laterally flattened); first glume either 3-5-nerved or 1-3-nerved.
..2 First glume 3-5 nerved (at least 3 nerves well-developed).
....3 Lemma awn 2-3 mm long; plant perennial; [native species of dry woodlands]; [section Bromopsis]
....3 Lemma awn 3-12 mm long (or 0-6 mm long in B. secalinus); plant annual; [introduced species of disturbed habitats]; [section Bromus].
......4 Panicle compact, the lateral branches erect or ascending, the pedicels < 10 mm long (shorter than the spikelets)
........5 Lemmas 3-5 mm wide; inflorescence ovoid in outline
........5 Lemmas 1.5-2 mm wide; inflorescence obovoid in outline
......4 Panicle relatively open, the lateral branches erect, ascending, or spreading, the pedicels > 15 mm long (longer than the spikelets).
..........6 Margins of the lemmas involute in fruit, wrapping around the grain, exposing the rachilla
..........6 Margins of the lemmas gaping, overlapping in fruit.
............ 7 Panicle branches erect or ascending, relatively stiff and straight
............ 7 Panicle branches spreading (at least the lower), either relatively stiff and straight, or flexuous and lax.
............ ..8 Panicle branches stiff; lemma awns 5-12 mm long, straight
............ ..8 Panicle branches flexuous and lax; lemma awns 7-15 mm long, flexuous
..2 First glume 1 (-3) nerved (only 1 nerve well-developed).
............ ....9 Longer lemma awns 10-60 mm long; plants annual; [introduced species of disturbed habitats]; [section Genea].
............ ......10 Panicle dense, spikelike
............ ......10 Panicle open, not spikelike.
............ ........11 First glume 13-20 mm long; second glume 20-30 mm long; lemma awns 35-60 mm long
............ ........11 First glume 5-14 mm long; second glume 8-17 mm long; lemma awns 10-30 mm long.
............ ..........12 First glume 7-14 mm long; second glume 9-17 mm long; lemma awns 18-30 mm long
............ ..........12 First glume 5-7 mm long; second glume 8-11 mm long; lemma awn (7-) 10-17 mm long
............ ....9 Longer lemma awns 1-6 (-8) mm long; plants perennial; [native and introduced species, collectively of disturbed and natural habitats]; [section Bromopsis].
............ ............ 13 Plants with creeping rhizomes, forming clonal colonies; both surfaces of leaves glabrous or glabrescent
............ ............ 13 Plants not strongly rhizomatous, the stems solitary or tufted; surfaces of leaf blades usually pubescent (sometimes sparsely so).
............ ............ ..14 Pedicels erect or ascending, mostly shorter than the spikelet; leaves 2-3 mm wide; [introduced, of disturbed habitats]
............ ............ ..14 Pedicels ascending at first, later arching-drooping, mostly longer than the spikelet; leaves 4-15 mm wide; [native, mostly of forests].
............ ............ ....15 Lemmas glabrous (or very minutely pubescent) on the back, hairy along the lower margins with long hairs
............ ............ ....15 Lemmas uniformly hairy over the entire back-surface (or rarely entirely glabrous).
............ ............ ......16 Culms with 10-20 leaves, often weak and leaning or reclining; junction of sheaths and base of leaf blades with 2 well-developed flanges prolonged into auricles or divergent spurs; second glume primarily 5-nerved; flowering late, with anthesis Aug-Oct
............ ............ ......16 Culms with 6-10 leaves, erect; junction of sheaths and base of leaf blades lacking flanges or auricles; second glume primarily 3-nerved; flowering earlier, anthesis from May-Aug.
............ ............ ........17 Lower surface of leaf with a conspicuous satiny sheen (when fresh); summit of sheath opposite the ligule with a conspicuous tuft of hairs
............ ............ ........17 Lower surface of leaf lacking a conspicuous satiny sheen; summit of sheath opposite the ligule lacking a conspicuous tuft of hairs