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• Microstegium vimineum

Microstegium vimineum — Japanese stiltgrass

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

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)

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae