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Key to Bromus

Poaceae

Bromus

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1
Lemmas compressed and strongly keeled (the whole spikelet thus strongly laterally flattened); first glume 3-9-nerved; [section Ceratochloa]
 ⇒ Bromus catharticus

(c) Fleming, Gary P.
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.

(c) Gunnar, Aaron - CC-BY
  2
First glume 3-5 nerved (at least 3 nerves well-developed).

(c) Ward, Scott G - CC-BY
    3
Lemma awns 2-3 mm long; plants perennial; [native species of dry woodlands]; [section Bromopsis]
 ⇒ Bromus kalmii

(c) Marcum, Paul
    3
Lemma awns 3-12 mm long (or 0-6 mm long in B. secalinus); plants annual; [introduced species of disturbed habitats]; [section Bromus].
      4
Panicle compact, the lateral branches erect or ascending (often densely ascendent in immature panicles), the pedicels < 10 mm long (shorter than the spikelets)

(c) Weakley, Alan - CC0
        5
Lemmas 11-20 long; spikelets 20-50 mm long; spikelets often arranged 2+ per inflorescence node; [LA and TX in our flora area]
 ⇒ Bromus lanceolatus
        5
Lemmas 6.5-11.0 mm long; spikelets (11-) 12-25 mm long, usually 1 per inflorescence node (spikelet congestion can obscure this character); [collectively widespread in our flora area including LA and TX].
          6
Lemmas 3-5 mm wide; inflorescence ovoid in outline, branches not verticillate.
          6
Lemmas 1.5-2 mm wide; inflorescence obovoid in outline, the branches sometimes verticillate.
 ⇒ Bromus scoparius
      4
Panicle relatively open, the lateral branches erect, ascending, or spreading, the pedicels > 15 mm long (longer than the spikelets).

(c) Chytrý, Milan - CC-BY
        8
Margins of the lemmas involute in fruit, wrapping around the grain, exposing the rachilla.

(c) Ward, Scott G - CC-BY
          9
Spikelets often purple-tinged; lower leaf sheaths bearing soft, appressed hairs; lemma awns 6-11 mm long
 ⇒ Bromus arvensis
          9
Spikelets not purple-tinged; lower leaf sheaths glabrous, loosely pubescent and glabrate, or evenly pilose; lemma awns 0-6 mm (sometimes awns absent or rudimentary)
 ⇒ Bromus secalinus
        8
Margins of the lemmas gaping, overlapping in fruit.
          10
Panicle branches erect or ascending, relatively stiff and straight
 ⇒ Bromus racemosus

(c) Richardson, Dave - CC-BY
          10
Panicle branches spreading (at least the lower), either relatively stiff and straight, or flexuous and lax.
             11
Panicle branches stiff; lemma awns 5-12 mm long, straight
 ⇒ Bromus commutatus
  2
First (lower) glume 1-nerved (occasionally with 3 nerves, but with only 1 nerve well-developed).
    12
Longer lemma awns 10-60 mm long; plants annual; [introduced species of disturbed habitats]; [section Genea].
      13
Panicle dense, spikelike and congested
 ⇒ Bromus rubens
      13
Panicle open, not spikelike.
        14
First glume 13-20 mm long; second glume 20-30 mm long; lemma awns 35-65 mm long
 ⇒ Bromus diandrus
        14
First glume 5-14 mm long; second glume 8-17 mm long; lemma awns 10-30 mm long.
          15
First glume 7-14 mm long; second glume 9-17 mm long; lemma awns 18-30 mm long; branches of the panicles variable (drooping, spreading or ascending)
 ⇒ Bromus sterilis
          15
First glume 5-7 mm long; second glume 8-11 mm long; lemma awn (7-) 10-17 mm long; branches of the panicles drooping
 ⇒ Bromus tectorum
    12
Longer lemma awns 1-6 (-8) mm long; plants perennial; [native and introduced species, collectively of disturbed and natural habitats]; [section Bromopsis].
      16
Plants with creeping rhizomes, forming clonal colonies; both surfaces of leaves glabrous or glabrescent
 ⇒ Bromus inermis
      16
Plants not strongly rhizomatous, the stems solitary or tufted; surfaces of leaf blades usually pubescent (sometimes sparsely so).
        17
Pedicels erect or ascending, mostly shorter than the spikelets; leaves 2-3 mm wide; [introduced, of disturbed habitats]
 ⇒ Bromus erectus
        17
Pedicels ascending at first, later arching-drooping, mostly longer than the spikelets; leaves (3-) 4-15 mm wide; [natives of forests, seepages and brushy areas excluding B. ramosus].
          18
Lemmas primarily glabrous on the abaxial surface (sometimes scabrous or with hirsute marginally in B. ciliatus but not uniformly pubescent).
             19
Plants perennial; culms 45-120 (-150) cm tall; basal sheaths usually pilose but upper sheaths glabrous; awns of the lemmas 3-5 mm long; [primarily northeastern US southward in the mountains to NC in our flora area]
 ⇒ Bromus ciliatus
             19
Plants annual; culms 30-70 cm tall; sheaths densely pubescent to pilose throughout; awns of the lemmas 4-8 mm long; [endemic to s. TX and n. Mexico]; [section Bromopsis)
 ⇒ Bromus texensis
          18
Lemmas either uniformly pubescent over the entire back-surface (or rarely entirely glabrous), or hairy across at least the lower half of the back-surface.
             20
Culms with 2-4 leaves; glumes usually glabrous (scabridulous on the veins); [rare waif, if indeed in our region]
 ⇒ Bromus ramosus
             20
Culms with 6-20 leaves; glumes pubescent (sometimes glabrous in some species); [natives, collectively widespread].
               21
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
 ⇒ Bromus latiglumis
               21
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.
                 22
Lower surface of leaf with a conspicuous satiny sheen (when fresh); summit of sheath opposite the ligule with a conspicuous tuft of hairs; upper glumes often 5-veined
 ⇒ Bromus nottowayanus
                 22
Lower surface of leaf lacking a conspicuous satiny sheen; summit of sheath opposite the ligule lacking a conspicuous tuft of hairs; upper glumes 3-veined
 ⇒ Bromus pubescens