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Microstegium vimineum — Japanese stiltgrass

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Facts

Japanese stiltgrass is a non-native grass found in riparian forests as well as fields and roadsides in Connecticut, Massachusetts and Rhode Island. It is a very invasive grass; native originally to Japan, India, Malaysia, and China, it has spread to many other areas around the world, including New Zealand, Nepal, South America, and Africa. It produces copious numbers of fruits on nodding inflorescences, which are easily dislodged and transported by water and animals (including humans). It is a straggling, annual grass that can spread by stolons. To identify it, look at the collar where the leaf sheath meets the stem; it will have ciliate hairs; also, its spikelets occur in pairs. This species uses the highly efficient C-4 photosynthetic pathway, which endows it with high growth rates and strong drought-tolerance.

Habitat

Anthropogenic (man-made or disturbed habitats), floodplain (river or stream floodplains), forests, fresh tidal marshes or flats, meadows and fields, shores of rivers or lakes

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
  • aquatic
  • terrestrial
  • wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf blade width
8–15 mm
Inflorescence branches
the flowers are attached to branches rather than to the main axis of the inflorescence
Spikelet length
3.7–6.5 mm
Glume relative length
one or both glumes are as long or longer than all of the florets
Awn on glume
  • the glume has an awn
  • the glume has no awn
One or more florets
there is one floret per spikelet
Lemma awn length
2–15 mm
Leaf ligule length
0.5–0.8 mm
Anther length
0.7–1 mm
Show all characteristics

  • Flowers

    Anther length
    0.7–1 mm
    Anther number
    0–3
    Awn on glume
    • the glume has an awn
    • the glume has no awn
    Floret lower bract texture
    the lemma is thin and flexible
    Glume relative length
    one or both glumes are as long or longer than all of the florets
    Glume shape
    the glume is flat or curved in cross-section
    Glume veins
    • 3
    • 5
    • 7 or more
    Inflorescence arrangement
    the spikelets are uniform
    Inflorescence axis orientation
    • the inflorescence axis is arched or curved outward
    • the inflorescence axis is straight
    Inflorescence branches
    the flowers are attached to branches rather than to the main axis of the inflorescence
    Inflorescence crowding
    NA
    Inflorescence type (general)
    the spikelets are borne on stalks or on branches
    Inflorescence type (specific)
    the inflorescence has pairs (or trios) of spikelets that are similar to each other in structure and size, with at least one of the spikelets on a stalk
    Lemma awn base
    the awn is attached right at the tip of the lemma
    Lemma awn length
    2–15 mm
    Lemma awn number
    • the lemma has no awn
    • the lemma has one awn on it
    Lemma cross-section
    the lemma is flat or rounded if you cut across the midpoint
    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
    One or more florets
    there is one floret per spikelet
    Spikelet axis tip
    there is no extension of the spikelet axis beyond the tip of the spikelet
    Spikelet disintegration
    the spikelet breaks off below the glumes
    Spikelet length
    3.7–6.5 mm
    Spikelets spiny
    the spikelets do not appear spiny

  • Leaves

    Leaf auricles
    the leaves do not have auricles
    Leaf blade width
    8–15 mm
    Leaf ligule length
    0.5–0.8 mm
    Leaf ligule type
    the leaf ligule is in the form of a membrane
    Leaf sheath closed around stem
    the margins of the leaf sheath are overlapping and not fused together except in the basal half (or less)
    Leaf sheath hairs
    there are no hairs on the surface of the leaf sheath

  • Place

    Habitat
    • aquatic
    • terrestrial
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • forests
    • fresh tidal marshes or flats
    • man-made or disturbed habitats
    • meadows or fields
    • river or stream floodplains
    • shores of rivers or lakes

  • Stem, shoot, branch

    Stem orientation
    the stems are upright
    Stem spacing
    the stems grow singly or a few together (they may form diffuse colonies)

Wetland status

Occurs in wetlands or non-wetlands. (Wetland indicator code: FAC)

In New England

Distribution

Connecticut
present, invasive, prohibited
Maine
present, prohibited
Massachusetts
present, invasive, prohibited
New Hampshire
present
Rhode Island
present
Vermont
present

Conservation status

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

Connecticut
not applicable (S-rank: SNA)
Massachusetts
not applicable (S-rank: SNA)

From Flora Novae Angliae dichotomous key

1.  Microstegium vimineum (Trin.) A. Camus E

Japanese stiltgrass. Andropogon vimineum Trin.; Eulalia viminea (Trin.) Kuntze • CT, MA, ME, NH, RI, VT. Riparian forests and terraces, fields, roadsides.

Native to North America?

No

Sometimes confused with

Eremochloa ophiuroides:
plants perennial, mat-forming, with stolons and axillary branches, leaf blades 1-5 mm wide, and pedicellate spikelet absent or rudimentary, not evident (vs. M. vimineum, with plants annual, straggling, often rooting at the nodes, leaf blades 8-15 mm wide, and pedicellate spikelet evident, with a bisexual upper floret).

Synonyms

  • Andropogon vimineum Trin.
  • Eulalia viminea (Trin.) Kuntze

Family

Poaceae

Genus

Microstegium