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Genus Bromus Family Poaceae

Description: Tufted or ascending annuals or perennials, occasionally rhizomatous.

Leaves with sheath with margins usually fused when young, hairy; ligule membranous; blade rolled in bud, usually narrow-linear, hairy or glabrous, often lax.

Inflorescence a dense or loose panicle of large spikelets.

Spikelets laterally compressed or only slightly so, rachilla disarticulating above the glumes and between the lemmas, several–many-flowered, upper florets often imperfect. Glumes unequal, acute, persistent. Lemmas 5–9-nerved, usually 2-toothed at the apex; awn, if present, arising from behind the teeth or dorsally near the tip, straight, bent or recurved; callus short. Paleas usually shorter than the lemma, the 2 keels ciliate or scabrid. Ovary with a terminal, hairy appendage and lateral styles; grain usually adherent to palea and tightly enclosed within the lemma.

Distribution and occurrence: World: c. 100 species, temperate regions, particularly Northern Hemisphere. Australia: 25 species (1 species native, 24 species naturalized), all States.

This genus has been divided several times in the past and there is still doubt about the names of some of the commonest weedy species. Key from Wheeler et al. (1990).

Text by S. W. L. Jacobs & S. M. Hastings
Taxon concept:

Taxa not yet included in identification key
Bromus coloratus,    Bromus japonicus,    Bromus squarrosus,    Bromus stamineus

 Key to the species 
1Awns 3.5–6 cm long; lemmas more than 2 cm longBromus diandrus
Awns, if present, to 3.5 cm long; lemmas not usually more than 2 cm long2
2Lemmas strongly compressed and keeled, often unawned3
Lemmas only slightly compressed if at all, rounded on the back, keel not as prominent; lemmas usually awned
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3Panicle compact with spikelets borne on short, erect branches; spikelets and leaves often dull, blue-green; common on sheep campsBromus brevis
Panicle more open with spikelets borne on long, often drooping branches; spikelets and leaves bright green; found in disturbed areas but not usually sheep camps. (Bromus stamineus also keys out here.)
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Bromus catharticus
4Plants rhizomatous; leaves glabrous; lemmas awnless or with short awns, 1–3 mm longBromus inermis
Plants without rhizomes, leaves usually hairy; lemmas with awns more than 4 mm long
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5Lower glume 1-nerved; spikelets wedge-shaped due to spreading of upper lemmas at maturity6
Lower glumes 3–5-nerved; spikelets usually lanceolate in outline as upper lemmas not usually divaricate
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6Panicle open with spreading, often drooping branches; spikelets nodding, not usually purplish7
Panicle dense and brush-like to moderately open but branches stiffly erect; spikelets often purplish
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7Spikelets (including awns) usually 4–6 cm long; lower branches of panicle with only 1 or 2 spikelets (panicle sometimes reduced to a raceme); annual or biennialBromus sterilis
Spikelets (with awns) usually less than 4 cm long; lower branches of panicle with 4 or more spikelets; annual
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Bromus tectorum
8Peduncle pubescent; panicle dense and much contracted; panicle branches 0.1–1 cm long and usually not visibleBromus rubens
Peduncle glabrous; panicle less dense with divaricate but always erect branches; panicle branches 1–3 or more cm long with most branches visible
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Bromus madritensis
9Panicle compact with spikelets erect on only slightly spreading branches10
Panicle open with spreading branches (panicle sometimes erect when first emerged but branches spread later), spikelets often drooping
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10Awn arising from c. 75% of way from lemma base to apex, twisted (often geniculate) and bent away from the spikelet; panicle dense, ovoid. (Bromus squarrosus also keys out here.)Bromus alopecuros
Awn usually subterminal, arising from top 25% of lemma (if arising 75% of way from lemma base then panicle open), straight, usually not twisted but may curve away from spikelets; panicle less dense than Bromus alopecuros
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11Lemmas glabrous or with short hairs less than 0.5 mm long; spikelets and panicle often narrowBromus racemosus
Lemmas hairy with hairs more than 1 mm long; spikelets and panicle broader than Bromus racemosus
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12Spikelets turgid, the lemmas broad, 8–11 mm long, often tapering abruptly to the tip, awn usually straightBromus hordeaceus
Spikelets more compressed with narrower elliptic lemmas 7–8 mm long, awns often curving outwards. (Bromus coloratus & B. hankianus also key out here.)
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Bromus molliformis
13Spikelets not usually exceeding 2.5 cm (including awns); lemmas 6–9 mm long, awns to 8 mm long, straight; pedicles not curvedBromus secalinus
Spikelets 2–4.6 cm long including awns; lemmas 10–15 mm long (sometimes spreading at maturity), awns more than 8 mm long, straight or bending away from the spikelet; pedicles slender and curved. (Bromus japonicus also keys out here.)
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Bromus arenarius

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