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Juncus marginatus — grass-leaved rush

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Facts

Grass-leaved rush, found in most of the eastern half of the United States, inhabits wet, sandy sites throughout New England. It is rather variable across its range.

Habitat

Anthropogenic (man-made or disturbed habitats), meadows and fields, shores of rivers or lakes, wetland margins (edges of wetlands)

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Stem shape in cross-section
the stem is round or oval in cross-section
Leaf blade width
1.3–3.5 mm
Leaf blade cross-section
the leaf blade is flat or rolled in at the edges
Inflorescence position
the inflorescence is at the tip of the plant
Inflorescence branching
the inflorescence is branched
Fruit type (general)
the fruit is a capsule, with at least three seeds in it
Fruit length
1.8–2.9 mm
Leaf position on plant
  • some leaf attachment points are above the midpoint of the stem
  • the attachment points of all the leaves are at or near the base of the plant
Perianth composition
the perianth is green or brown, with six sepal-like parts, and a leafy texture
Fruit cross-section
the fruit is triangular to terete (circular) in cross-section
Show all characteristics

  • Flowers

    Anther color (dry)
    the anthers range in color from white to tan or yellow to yellow-brown
    Anther length
    0.2–0.7 mm
    Floral bristle color
    NA
    Floral bristle number
    NA
    Floral bristle relative length
    NA
    Floral bristles
    NA
    Floral scale hairs
    NA
    Floral scale length
    0 mm
    Floral scale nerves
    NA
    Flower number per cluster
    • 1
    • 2-5
    • 5-20
    Inflorescence bract angle
    the bracts are vertical or angled only slightly outwards
    Inflorescence bract number
    there are two to five bracts per inflorescence
    Inflorescence bract position (Sparganium)
    NA
    Inflorescence bracts
    there are at least two bracts, and they are either flat or folded or rolled in at the edges
    Inflorescence branching
    the inflorescence is branched
    Inflorescence crowding
    • the inflorescence is at least somewhat spread out, with at least one branch coming from the main stem
    • the inflorescence is crowded together in one tight cluster
    Inflorescence position
    the inflorescence is at the tip of the plant
    Inflorescence shape
    the aggregations within the inflorescence are roughly circular (not flattened) in cross-section
    Inflorescence type
    there are two or more flowers, spikes or flower clusters on a branched inflorescence
    Perianth composition
    the perianth is green or brown, with six sepal-like parts, and a leafy texture
    Stamen length
    1.4–3.7 mm
    Stamen number
    3
    Stigma number
    3
    floral bristle barbs
    NA

  • Fruits or seeds

    Achene beak length
    0 mm
    Achene surface texture
    NA
    Achene tubercle relative width
    NA
    Achene tubercle width
    0 mm
    Capsule relative length
    • the capsule is about equal to the perianth
    • the capsule is longer thant he perianth
    • the capsule is shorter than the perianth
    Fruit cross-section
    the fruit is triangular to terete (circular) in cross-section
    Fruit length
    1.8–2.9 mm
    Fruit type (general)
    the fruit is a capsule, with at least three seeds in it
    Fruit type (specific)
    the fruit is a capsule (splits along two or more seams, apical teeth or pores when dry, to release two or more seeds)
    Locules in capsule
    the capsule has three locules
    Seed length
    0.4–0.7 mm
    Seed tail relative length
    0.4–0.7 mm
    Seed tails
    there is no tail on the seeds
    Tubercle height
    0 mm

  • Growth form

    Lifespan
    the plant lives more than two years
    Underground organs
    • the plant has a rhizome (a horizontal underground stem with roots growing from it)
    • there are only slender roots on the plant

  • Leaves

    Auricle length
    0.5–1.5 mm
    Auricle texture
    the auricles are weak, papery and translucent
    Auricles
    the leaf sheath has auricles on it
    Leaf blade cross-section
    the leaf blade is flat or rolled in at the edges
    Leaf blade length
    200–450 mm
    Leaf blade width
    1.3–3.5 mm
    Leaf form
    all the leaves hold their form out of water
    Leaf position on plant
    • some leaf attachment points are above the midpoint of the stem
    • the attachment points of all the leaves are at or near the base of the plant
    Leaf septa
    the leaf blades do not have transverse septa
    Leaf sheath hairs
    the leaf sheathes are without hairs
    Pedicel length (Typha)
    0 mm
    Stem leaf blade ligules
    there are no ligules at the leaf blade bases
    Stem leaf blades
    there are fully-developed leaves with leaf blades on the main stem

  • Place

    Habitat
    wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • edges of wetlands
    • man-made or disturbed habitats
    • meadows or fields
    • shores of rivers or lakes

  • Stem, shoot, branch

    Plant height
    30–130 cm
    Stem shape in cross-section
    the stem is round or oval in cross-section
    Stem texture near tip
    the stem feels smooth near the tip

Wetland status

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

In New England

Distribution

Connecticut
present
Maine
present
Massachusetts
present
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.

Massachusetts
widespread (S-rank: S5)
Vermont
uncommon (S-rank: S3)

From Flora Novae Angliae dichotomous key

25.  Juncus marginatus Rostk. N

grass-leaved rush. CT, MA, ME, NH, RI, VT. Low fields, pond shores, edges of pools, abandoned borrow pits, often on moist to wet sand.

Native to North America?

Yes and no (some introduced)

Sometimes confused with

Juncus biflorus:
widest leaf blades mostly 3.1–4.5 mm wide, anthers mostly 0.6–1 mm long, exserted beyond tepals, and sheath of lowest leaf mostly 43–78 mm long (vs. J. marginatus, with widest leaf blades mostly 1.6–2.6 mm wide, anthers mostly 0.3–0.5 mm long, concealed by the tepals, and sheath of lowest leaf mostly 22–38 mm long).

Family

Juncaceae

Genus

Juncus