Juncus acuminatus — sharp-fruited rush
![Inflorescences: Juncus acuminatus. ~ By Arthur Haines. ~ Copyright © 2024 Arthur Haines. ~ arthur.d.haines[at]gmail.com](https://newfs.s3.amazonaws.com/taxon-images-1000s1000/Juncaceae/juncus-acuminatus-in-ahaines.jpg)
Copyright: various copyright holders. To reuse an image, please click it to see who you will need to contact.
Facts
Sharp-fruited rush ranges from Maine and Washington to Central America. It is found in fresh to brackish tidal river shores and marshes in all New England states.
Habitat
Brackish or salt marshes and flats, fresh tidal marshes or flats, marshes, shores of rivers or lakes, wetland margins (edges of wetlands)
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
-
- aquatic
- terrestrial
- 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
- 0.5–3 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
- 2.8–4 mm
- Leaf position on plant
- some leaf attachment points are above the midpoint of the stem
- 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
-
- 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
- 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 length
- 1.3–2 mm
- Stamen number
- 3
- Stigma number
- 3
- Style division
- the top two thirds of the style is divided
- 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
- Fruit cross-section
- the fruit is triangular to terete (circular) in cross-section
- Fruit length
- 2.8–4 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
- 0.3–0.4 mm
- Seed tail relative length
- 0.3–0.4 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
- 1–2 mm
- Underground organs
-
- the plant has a rhizome (a horizontal underground stem with roots growing from it)
- there are only slender roots on the plant
-
Leaves
- Auricle length
- 1–1.5 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
- 10–400 mm
- Leaf blade width
- 0.5–3 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
- 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
- 10–70 mm
-
Place
- Habitat
-
- aquatic
- terrestrial
- wetlands
- New England state
-
- Connecticut
- Maine
- Massachusetts
- New Hampshire
- Rhode Island
- Vermont
- Specific habitat
-
- brackish or salt marshes and flats
- edges of wetlands
- fresh tidal marshes or flats
- marshes
- shores of rivers or lakes
-
Stem, shoot, branch
- Plant height
- 14–100 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
- 0.5–3 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
- widespread (S-rank: S5)
- Vermont
- extremely rare (S-rank: S1)
From Flora Novae Angliae dichotomous key
1. Juncus acuminatus Michx. N
sharp-fruited rush. Juncus pelocarpus E. Mey. var. crassicaudex Engelm. • CT, MA, ME, NH, RI, VT. Fresh to brackish-tidal river shores, marshes.
Native to North America?
Yes
Sometimes confused with
- Juncus articulatus:
- capsules brown to dark brown and stems occurring singly or few together (vs. J. acuminatus, with capsules light brown and stems clumped together).
- Juncus debilis:
- tepals evidently shorter than the mature capsules, 1.8-2.5 mm long (vs. J. acuminatus, with tepals nearly or fully as long as the capsules and tepals 2.6-3.9 mm long).
Synonyms
- Juncus pelocarpus E. Mey. var. crassicaudex Engelm.