Juncus filiformis L.

thread rush

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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

Thread rush has a circumboreal distribution, but is sparse and rare in much of its range. A dramatic cultivar with corkscrew-shaped stems has become a popular wetland ornamental in horticulture.

Habitat

Alpine or subalpine zones, ridges or ledges, shores of rivers or lakes

Characteristics

Habitat
  • terrestrial
  • wetlands
New England state
  • Maine
  • Massachusetts
  • New Hampshire
  • Vermont
Stem shape in cross-section
the stem is round or oval in cross-section
Leaf blade width
0 mm
Leaf blade cross-section
NA
Inflorescence position
the inflorescence appears to come from the side of the plant because the involucral bract at its base looks like an extension of the main stem
Inflorescence branching
the inflorescence is branched
Fruit type (general)
the fruit is a capsule, with at least three seeds in it
Fruit length
2.5–3 mm
Leaf position on plant
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
    0.5–0.7 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
    • 2-5
    • 5-20
    Inflorescence bract angle
    the bracts are vertical or angled only slightly outwards
    Inflorescence bract number
    there is just one bract on the inflorescence
    Inflorescence bract position (Sparganium)
    NA
    Inflorescence bracts
    there is only one bract, and it looks like a continuation of the stem
    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 appears to come from the side of the plant because the involucral bract at its base looks like an extension of the main stem
    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
    1–1.6 mm
    Stamen number
    4-6
    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 shorter than the perianth
    Fruit cross-section
    the fruit is triangular to terete (circular) in cross-section
    Fruit length
    2.5–3 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
    0.5–0.6 mm
    Seed tail relative length
    0.5–0.6 mm
    Seed tails
    there is no tail on the seeds
    Tubercle height
    0 mm
  • Growth form
    Lifespan
    the plant lives more than two years
    Rhizome thickness
    1.5–2 mm
    Underground organs
    the plant has a rhizome (a horizontal underground stem with roots growing from it)
  • Leaves
    Auricle length
    0 mm
    Auricle texture
    NA
    Auricles
    NA
    Leaf blade cross-section
    NA
    Leaf blade length
    0 mm
    Leaf blade width
    0 mm
    Leaf form
    all the leaves hold their form out of water
    Leaf position on plant
    the attachment points of all the leaves are at or near the base of the plant
    Leaf septa
    NA
    Leaf sheath hairs
    the leaf sheathes are without hairs
    Pedicel length (Typha)
    0 mm
    Stem leaf blade ligules
    NA
    Stem leaf blades
    there are no leaves on the main stem, or there is a small tooth or tiny blade, or a leaf sheath with no blade
  • Place
    Habitat
    • terrestrial
    • wetlands
    New England state
    • Maine
    • Massachusetts
    • New Hampshire
    • Vermont
    Specific habitat
    • alpine or subalpine zones
    • ridges or ledges
    • shores of rivers or lakes
  • Stem, shoot, branch
    Plant height
    2–35 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
    Stem thickness at midpoint
    1 mm

Wetland Status

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

New England Distribution and Conservation Status

Distribution

Connecticut
absent
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
extremely rare (S-rank: S1), endangered (code: E)

Native to North America?

Yes

Sometimes Confused With

Juncus pylaei:
stems cespitose and flowers with 3 stamens (vs. J. filiformis, with stems produced singly or few-together from rhizomes and flowers with 6 stamens).

Family

Juncaceae

Genus

Juncus

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Information from Dichotomous Key of Flora Novae Angliae

21.  Juncus filiformis L. N

thread rush. MA, ME, NH, VT. Low, wet sandy areas, river shores, peaty and gravelly pond 
shores, rarely on alpine ridges and plateaus.