Juncus filiformis — thread rush
![Inflorescences: Juncus filiformis. ~ By Arthur Haines. ~ Copyright © 2024 Arthur Haines. ~ arthur.d.haines[at]gmail.com](https://newfs.s3.amazonaws.com/taxon-images-1000s1000/Juncaceae/juncus-filiformis-in-ahaines-b.jpg)
![Flowers and fruits: Juncus filiformis. ~ By Arthur Haines. ~ Copyright © 2024 Arthur Haines. ~ arthur.d.haines[at]gmail.com](https://newfs.s3.amazonaws.com/taxon-images-1000s1000/Juncaceae/juncus-filiformis-ff-ahaines-c.jpg)
![Inflorescences: Juncus filiformis. ~ By Arthur Haines. ~ Copyright © 2024 Arthur Haines. ~ arthur.d.haines[at]gmail.com](https://newfs.s3.amazonaws.com/taxon-images-1000s1000/Juncaceae/juncus-filiformis-in-ahaines-a.jpg)
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Facts
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
New England distribution
Adapted from BONAP data
Native: indigenous.
Non-native: introduced (intentionally or unintentionally); has become naturalized.
County documented: documented to exist in the county by evidence (herbarium specimen, photograph). Also covers those considered historical (not seen in 20 years).
State documented: documented to exist in the state, but not documented to a county within the state. Also covers those considered historical (not seen in 20 years).
Note: when native and non-native populations both exist in a county, only native status is shown on the map.
Found this plant? Take a photo and post a sighting.
enlargeCharacteristics
- 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
-
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)
In New England
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)
From Flora Novae Angliae dichotomous key
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.
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).