Juncus nodosus — knotted rush
![Inflorescences: Juncus nodosus. ~ By Arthur Haines. ~ Copyright © 2024 Arthur Haines. ~ arthur.d.haines[at]gmail.com](https://newfs.s3.amazonaws.com/taxon-images-1000s1000/Juncaceae/juncus-nodosus-in-ahaines.jpg)
![Leaves and auricles: Juncus nodosus. ~ By Bud Kovalchik. ~ Copyright © 2024 Bud Kovalchik. ~ bkovalchik7[at]gmail.com ~ U. of Washington - WTU - Herbarium - biology.burke.washington.edu/herbarium/imagecollection.php](https://newfs.s3.amazonaws.com/taxon-images-1000s1000/Juncaceae/juncus-nodosus-la-bkovalchik.jpg)
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Facts
Knotted rush is found in much of North America and in all New England states, in calcareous situations on river shores, pools, and lakesides.
Habitat
Floodplain (river or stream floodplains), meadows and fields, shores of rivers or lakes, swamps
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
- 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
- 0.5–1.5 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
- 3.2–5 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
-
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
- 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
-
- 5-20
- more than 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
- 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
-
- 3
- 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
- 3.2–5 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 capsule has one locule
- Seed length
- 0.4–0.5 mm
- Seed tail relative length
- 0.4–0.5 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 mm
- Underground organs
- the plant has a rhizome (a horizontal underground stem with roots growing from it)
-
Leaves
- Auricle length
- 0.5–1.7 mm
- Auricle texture
- the auricles are firm (though flexible) and opaque
- 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
- 60–300 mm
- Leaf blade width
- 0.5–1.5 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 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
- 6–12 mm
-
Place
- Habitat
- wetlands
- New England state
-
- Connecticut
- Maine
- Massachusetts
- New Hampshire
- Rhode Island
- Vermont
- Specific habitat
-
- meadows or fields
- river or stream floodplains
- shores of rivers or lakes
- swamps
-
Stem, shoot, branch
- Plant height
- 4–70 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
- 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
- unranked (S-rank: SNR)
From Flora Novae Angliae dichotomous key
27. Juncus nodosus L. N
knotted rush. CT, MA, ME, NH, RI, VT. River shores, especially in seeps and also pools associated with outcrops, lake shores, meadows, usually in regions of high-pH bedrock and till. Known in other regions to hybridize with Juncus alpinoarticulatus.
Native to North America?
Yes and no (some introduced)
Sometimes confused with
- Juncus torreyi:
- auricles mostly 2–4 mm long, scarious, pale brown, and glomerules composed of 25-100 flowers (vs. J. nodosus, with auricles mostly 0.5–1 mm long, cartilaginous, dark yellow, and glomerules composed of mostly 6–25 flowers).
- Juncus acuminatus:
- plants cespitose, without elongate rhizomes and tepals lanceolate to narrow-ovate (vs. J. nodosus, the plants not cespitose, the stems produced singly or a few together from elongate rhizomes, and tepals subulate).