Juncus nodosus L.

knotted 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

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

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
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
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
    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)

New England Distribution and Conservation Status

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), #NAME? (code: #NAME?)

var. nodosus

Massachusetts
unranked (S-rank: SNR)

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).

Family

Juncaceae

Genus

Juncus

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Information from Dichotomous Key of Flora Novae Angliae

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.