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Juncus alpinoarticulatus — northern green rush

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Facts

Northern green rush is a circumboreal rush found in northern New England on lake and river shores and marshes on calcareous bedrock. Succession and changes to hydrological regimes are the greatest threats to this rare species.

Habitat

Fens, fresh tidal marshes or flats, marshes, 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
wetlands
New England state
  • Maine
  • New Hampshire
  • Vermont
Stem shape in cross-section
the stem is round or oval in cross-section
Leaf blade width
0.5–1.1 mm
Leaf blade cross-section
the leaf blade is elliptic or circular in cross-section
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
2.3–3.5 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
    Floral bristle color
    NA
    Floral bristle number
    • 0
    • 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 are two to five bracts per inflorescence
    • 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
    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 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 about equal to the perianth
    • the capsule is longer thant he perianth
    Fruit cross-section
    the fruit is triangular to terete (circular) in cross-section
    Fruit length
    2.3–3.5 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 three internal walls do not meet in the center
    Seed length
    0.5–0.7 mm
    Seed tail relative length
    0.5–0.7 mm
    Seed tails
    there is no tail on the seeds
    Tubercle height
    0 mm

  • Growth form

    Lifespan
    the plant lives more than two years
    Rhizome thickness
    2–4 mm
    Underground organs
    the plant has a rhizome (a horizontal underground stem with roots growing from it)

  • Leaves

    Auricle length
    0.5–1.2 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 elliptic or circular in cross-section
    Leaf blade length
    15–120 mm
    Leaf blade width
    0.5–1.1 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
    Width of seed-producing inflorescence
    2–6 mm

  • Place

    Habitat
    wetlands
    New England state
    • Maine
    • New Hampshire
    • Vermont
    Specific habitat
    • fens
    • fresh tidal marshes or flats
    • marshes
    • meadows or fields
    • shores of rivers or lakes

  • Stem, shoot, branch

    Plant height
    5–50 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
    1–3 mm

Wetland status

Occurs only in wetlands. (Wetland indicator code: OBL)

In New England

Distribution

Connecticut
absent
Maine
present
Massachusetts
absent
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.

ssp. americanus

Maine
uncommon (S-rank: S3), special concern (code: SC)
Maine
uncommon (S-rank: S3)
New Hampshire
extremely rare (S-rank: S1), endangered (code: E)
Vermont
rare (S-rank: S2)

Subspecies and varieties

Our subspecies is Juncus alpinoarticulatus Chaix ex Vill. ssp. americanus.

From Flora Novae Angliae dichotomous key

2.  Juncus alpinoarticulatus Chaix ex Vill. ssp. americanus (Farw.) Hämet-Ahti NC

northern green rush. Juncus alpinoarticulatus Vill. ssp. nodulosus (Wahlenb.) Hämet-Ahti, sensu American authors; J. alpinus Vill. var. americanus Farw.; J. alpinus Vill. var. rariflorus Hartman, sensu American authors • ME, NH, VT; also reported from MA by Hämet-Ahti (1986), but specimens are unknown. Lake shores and ice-scoured river shores in regions of high-pH bedrock or till, fresh-tidal river marshes, fen-like meadows. Known in other regions to hybridize with Juncus articulatus, J. brevicaudatus, and J. nodosus (among others).

Native to North America?

Yes

Sometimes confused with

Juncus articulatus:
capsules usually acute at apex, inner tepals acute to acuminate at apex, and branches of inflorescence widely ascending to spreading (vs. J. alpinoarticulatus, with capsules rounded to obtuse at apex, with a mucronate tip, inner tepals acute to obtuse at apex, and branches of inflorescence strictly ascending).
Juncus brachycephalus:
seeds 0.8-1.2 mm long with short, pale appendages at each end, and capsule acute at apex (vs. J. alpinoarticulatus, with seeds 0.5-0.7 mm long, lacking pale appendages at each end, and capsule rounded to obtuse at apex).

Synonyms

  • Juncus alpinoarticulatus Vill. ssp. nodulosus (Wahlenb.) Hämet-Ahti, sensu American authors
  • Juncus alpinus Vill. var. americanus Farw.
  • Juncus alpinus Vill. var. rariflorus Hartman, sensu American authors

Family

Juncaceae

Genus

Juncus