Carex kobomugi Ohwi

Japanese sedge

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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 sedge is native to East Asia and introduced on sandy beaches in Massachusetts and Rhode Island. Although it is prohibited in Massachusetts, clones of Japanese sedge are being used for dune stabilization elsewhere, so the range of this invasive species will likely expand.

Habitat

Anthropogenic (man-made or disturbed habitats), coastal beaches (sea beaches)

Characteristics

Habitat
terrestrial
New England state
  • Massachusetts
  • Rhode Island
stem leaf blade width
4–8 mm
Lowest bract sheath
the lowest bract has no sheath (or a very short sheath up to four millimeters in length)
Spike on stalk
the lowest spike on the plant is not borne on a peduncle
Top spike
  • entirely carpellate
  • the uppermost spike contains both staminate and carpellate flowers, with the carpellate flowers located below, or intermixed with, the staminate flowers
  • the uppermost spike contains only staminate flowers
Perigynium hairs
the perigynium has no hairs
Perigynium length
10–14 mm
Leaf sheath color
the leaf sheath has no pink, red or purple tinting
Leaf blade texture
the leaf blade is smooth and hairless, or rough and sandpapery
Perigynium beak teeth
the perigynium beak is divided at the top into two teeth
Show All Characteristics
  • Flowers
    Anther length
    4–6.5 mm
    Bumps on fruit
    there are no papillae on the perigynium surface
    Length of scale
    the scale is nearly as long as, or longer than, the perigynium
    Lowest spike length
    30–60 mm
    Lowest spike stalk length
    0 mm
    Lowest spike width
    20–40 mm
    Perigynium beak
    the perigynium has a beak
    Perigynium beak orientation
    the beak of the perigynium is straight, and in line with the perigynium
    Perigynium beak serrations
    the perigynium beak has no serrations
    Perigynium beak teeth
    the perigynium beak is divided at the top into two teeth
    Perigynium beak teeth length
    At least 0.4 mm
    Perigynium color
    • brown
    • tan
    Perigynium cross-section
    the perigynium is planoconvex (flat on one surface and rounded on the other) in cross-section
    Perigynium hairs
    the perigynium has no hairs
    Perigynium length
    10–14 mm
    Perigynium nerve texture
    the nerves on the perigynium are raised, even after drying the perigynium
    Perigynium orientation
    the perigynia are oriented vertically or pressed against the axis or adjacent perigynia
    Perigynium shape
    the perigynium body is ovate (egg-shaped)
    Perigynium winged
    the perigynium has wings on it
    Pollen- and seed-producing spikes
    • all the spikes produce only pollen
    • some of the spikes produce perigynia
    Pollen-producing spike length
    30–40 mm
    Pollen-producing spike number
    0–1
    Pollen-producing spike peduncle length
    0 mm
    Pollen-producing spike width
    10–20 mm
    Scale awn
    the carpellate scale has an awn on it
    Scale color
    • green
    • other
    Scale tip
    the carpellate scale tip is acuminate (tapered to a narrow point)
    Spike on stalk
    the lowest spike on the plant is not borne on a peduncle
    Spike orientation
    the spikes are oriented vertically or pressed against the axis
    Spikes per stem
    more than 15
    Stigma branching
    the stigmas have three branches
    Top spike
    • entirely carpellate
    • the uppermost spike contains both staminate and carpellate flowers, with the carpellate flowers located below, or intermixed with, the staminate flowers
    • the uppermost spike contains only staminate flowers
  • Fruits or seeds
    Achene dimples
    the achene has no folds or dimples
    Achene length
    4–7 mm
    Achene width
    1.5–2.5 mm
    Style persistence
    the style falls off the mature achenes
  • Growth form
    Rhizomes
    there are long rhizomes present
  • Leaves
    Leaf arrangement
    the leaves are all produced from the base of the plant
    Leaf blade cross-section
    The leaf blade is folded lengthwise, with one prominent midvien
    Leaf blade texture
    the leaf blade is smooth and hairless, or rough and sandpapery
    Leaf bumps
    the upper surface of the leaf blade does not have papillae
    Leaf sheath bumps
    there are no papillae at the top edge of the leaf sheath
    Leaf sheath color
    the leaf sheath has no pink, red or purple tinting
    Leaf sheath dots
    there are no dots on the leaf sheathes
    Leaf sheath folds
    there are no corrugations on the leaf sheath
    Leaf sheath texture
    the leaf sheath feels smooth, and has no hairs
    Lowest bract sheath
    the lowest bract has no sheath (or a very short sheath up to four millimeters in length)
    Lowest leaf blade width
    4–8 mm
    Lowest leaf sheath texture
    the leaf sheath feels smooth (it may have soft hairs)
    stem leaf blade width
    4–8 mm
  • Place
    Habitat
    terrestrial
    New England state
    • Massachusetts
    • Rhode Island
    Specific habitat
    • man-made or disturbed habitats
    • sea beaches
  • Stem, shoot, branch
    Plant height
    10–30 cm
    Relative stem height
    the main stem is equal to or shorter than the leaves
    Stem cross-section
    the main stem is roughly triangular in cross-section
    Stem spacing
    the stems grow singly or a few together (they may form diffuse colonies)

Wetland Status

Not classified

New England Distribution and Conservation Status

Distribution

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

Conservation Status

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

Massachusetts
not applicable (S-rank: SNA)

Native to North America?

No

Synonyms

  • Carex macrocephala Willd. ex Spreng. var. kobomugi (Ohwi) Miyabe & Kudô

Family

Cyperaceae

Genus

Carex

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Information from Dichotomous Key of Flora Novae Angliae

113.  Carex kobomugi Ohwi E

Japanese sedge. Carex macrocephala Willd. ex Spreng. var. kobomugi (Ohwi) Miyabe & Kudô 
• MA, RI. Sandy beaches and dunes of the Atlantic coast, borrow pits near the Atlantic coast.