Bromus japonicus Thunb. ex Murr.

Japanese brome

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New England Distribution

Adapted from BONAP data

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North America Distribution

Adapted from BONAP data

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Facts About

Japanese brome is a Eurasian annual, widely introduced in North America and considered a noxious weed on rangelands and prairies where it competes with native perennials for water and nutrients. In New England it is found in fields, roadsides and disturbed sites.

Habitat

Anthropogenic (man-made or disturbed habitats), meadows and fields

Characteristics

Habitat
terrestrial
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Vermont
Leaf blade width
2–4 mm
Inflorescence branches
the flowers are attached to branches rather than to the main axis of the inflorescence
Spikelet length
20–40 mm
Glume relative length
neither glume is quite as long as all of the florets
Awn on glume
the glume has no awn
One or more florets
there is more than one floret per spikelet
Lemma awn length
8–13 mm
Leaf sheath hair type
  • there are hairs on the surface of the leaf sheath, but the hairs do not have blisters at their bases
  • there are no hairs on the surface of the leaf sheath
Leaf ligule length
1–2.2 mm
Anther length
Up to 1.5 mm
Show All Characteristics
  • Flowers
    Anther length
    Up to 1.5 mm
    Anther number
    2–3
    Awn on glume
    the glume has no awn
    Bristles below spikelets
    no
    Floret lower bract texture
    the lemma is thin and flexible
    Floret number
    6–12
    Floret types within spikelet
    all the florets within a spikelet are similar
    Glume awn length
    0 mm
    Glume keel
    the glume keels are rough or hairy
    Glume relative length
    neither glume is quite as long as all of the florets
    Glume shape
    the glume is V-shaped in cross-section
    Glume veins
    • 3
    • 5
    • 7 or more
    Glumes per spikelet
    2
    Inflorescence arrangement
    the spikelets are uniform
    Inflorescence axis orientation
    • the inflorescence axis bends downwards or hangs
    • the inflorescence axis is arched or curved outward
    Inflorescence branch length
    5–10 cm
    Inflorescence branch roughness
    the inflorescence branches are somewhat to very rough
    Inflorescence branches
    the flowers are attached to branches rather than to the main axis of the inflorescence
    Inflorescence branches coming off the lowest stem node
    3–5
    Inflorescence crowding
    the panicle is somewhat to very spread out, with clearly-evident branches
    Inflorescence length
    100–220 mm
    Inflorescence length to width ratio
    1.7–2.5
    Inflorescence type (general)
    the spikelets are borne on stalks or on branches
    Inflorescence type (specific)
    the inflorescence is branched, and the branches do NOT both grow from the same side of the plant AND look like spikes
    Inflorescence width
    40–130 mm
    Inforescence position
    the spikelets are mainly carried at the end of the stem
    Lemma awn base
    the awn is attached at the upper half of the lemma
    Lemma awn coiled
    • the lemma awn is coiled at least one half turn
    • the lemma awn is straight or twisted, but not coiled one half turn
    Lemma awn length
    8–13 mm
    Lemma awn number
    the lemma has one awn on it
    Lemma awn orientation
    • the awn of the lemma is straight
    • the awn of the lemma on dried or older plants is curved or bent outwards
    Lemma base hair length
    0 mm
    Lemma base hairs
    the lemma is hairless or feels just a tiny bit rough at the base
    Lemma cross-section
    the lemma is flat or rounded if you cut across the midpoint
    Lemma hairs
    the lemma is hairless between the veins
    Lemma keel hairs
    NA
    Lemma marginal vein hairs
    the marginal vein of the lemma is hairless
    Lemma surface
    the surface of the lemma is relatively smooth (not counting any longitudinal veins or hairs)
    Lemma tip
    the lemma tip is split into two or more points
    Lemma vein number
    7 or more
    Lemma vein orientation
    the veins on the lemma come together near the tip
    Lower glume length
    4.5–7 mm
    One or more florets
    there is more than one floret per spikelet
    Palea relative length
    palea is one half to fully as long as lemma
    Reproductive system
    all the flowers on the plant have both carpels and stamens (synoecious)
    Spikelet axis tip
    there is an extension of the spikelet axis beyond the tip of the spikelet
    Spikelet disintegration
    the spikelet breaks off above the glumes, so that after the florets fall off, the glumes remain
    Spikelet length
    20–40 mm
    Spikelet number per node
    Up to 0
    Spikelet pedicel
    the spikelets have pedicels
    Spikelet shape
    the spikelets are lanceolate (lance-shaped, widest below the middle and tapering narrowly to the ends) in profile
    Spikelet width
    8–10 mm
    Spikelets per panicle branch
    1–4
    Spikelets spiny
    the spikelets do not appear spiny
    Tip of glume
    • the tip of the glume is divided into two or more points
    • the tip of the glume is not divided (though it may have an awn on it)
    Upper glume length
    5–8 mm
    Upper glume relative length
    the upper glume is more than one half as long as the lowest lemma
    Upper glume shape
    the upper glume is widest at or below the middle
  • Fruits or seeds
    Groove on seed
    the caryopsis has a groove running most of its length
    Seed length
    7–8 mm
  • Growth form
    Horizontal rooting stem
    no
    Lifespan
    the plant lives only a single year or less
    Rhizomes
    no
    Roots
    there are only slender roots on the plant
  • Leaves
    Leaf blade cross-section
    the leaf blade is more or less flat in cross-section, or slightly folded or rolled inwards
    Leaf blade hairs
    • the leaf blade is hairless, but it may have tiny prickles that give it a sand-papery feel
    • the leaf blade is hairy
    Leaf blade length
    10–20 cm
    Leaf blade texture
    the leaf blade is rough and sandpapery
    Leaf blade width
    2–4 mm
    Leaf ligule length
    1–2.2 mm
    Leaf ligule type
    the leaf ligule is in the form of a membrane
    Leaf margin glands
    there are no glands along the edges of the leaf blade
    Leaf sheath closed around stem
    the margins of the leaf sheath are fused together and form a closed tube except (possibly) at the very top
    Leaf sheath hair type
    • there are hairs on the surface of the leaf sheath, but the hairs do not have blisters at their bases
    • there are no hairs on the surface of the leaf sheath
    Leaf sheath hairs
    there are hairs on the surface of the leaf sheath
    Orientation of topmost leaf
    the flag leaf is held upright, or at less than a 45 degree angle out from the stem
  • Place
    Habitat
    terrestrial
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Vermont
    Specific habitat
    • man-made or disturbed habitats
    • meadows or fields
  • Stem, shoot, branch
    Hairs at nodes
    • the stem nodes are hairless or they have very sparse hairs
    • the stem nodes have hairs that stand out at a shallow angle, or they curve downwards
    Plant height
    22–70 cm
    Stem hairs
    • the stem has hairs on it
    • the stem is nearly to completely hairless
    Stem orientation
    • the stems are upright
    • the stems trail at the base, but turn upwards at the tips

Wetland Status

Usually occurs in non-wetlands, but occasionally in wetlands. (Wetland indicator code: FACU)

New England Distribution and Conservation Status

Distribution

Connecticut
present
Maine
present
Massachusetts
present
New Hampshire
present
Rhode Island
absent
Vermont
present

Conservation Status

Exact status definitions can vary from state to state. For details, please check with your state.

Massachusetts
unranked (S-rank: SNR)

Native to North America?

No

Sometimes Confused With

Bromus commutatus:
branches of panicle stiffly erect to spreading, apical lobes of lemma up to 1.5 mm long, and lemma awns terete or scarcely flattened at the base, not or only slightly divergent at maturity (vs. B. japonicus, with branches of panicle using arching or dropping, apical lobes of lemma 1.5-3 mm long, and lemma awns broad and flattened at base, divergent at maturity).
Bromus squarrosus:
panicle often somewhat secund, with simple branches, spikelets with 8-30 florets, and lemmas 2.5-3.5 mm deep in side view (vs. B. japonicus, with the panicle not secund, with branched lower branches, spikelets with 6-12 florets, and lemmas 1.2-2.2 mm deep in side view).

Family

Poaceae

Genus

Bromus

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Information from Dichotomous Key of Flora Novae Angliae

8.  Bromus japonicus Thunb. ex Murr. E

Japanese brome. CT, MA, ME, NH, VT. Fields, roadsides, disturbed soil.