Dulichium arundinaceum (L.) Britt.

three-way sedge

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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

Three-way sedge is the only member of its genus in New England. It inhabits river and lake shores and open wetlands. It is easily recognizable by its three ranked leaves. The three lines of leaves can be seen by looking down the stem from the top.

Habitat

Marshes, shores of rivers or lakes, wetland margins (edges of wetlands)

Characteristics

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
3.5–8 mm
Leaf blade cross-section
the leaf blade is flat or rolled in at the edges
Inflorescence position
the inflorescence emerges from an axil, or most of its parts do so
Inflorescence branching
the inflorescence is on one or more stems with no branches
Fruit type (general)
the fruit is like a seed, and surrounded by scales
Fruit length
2–4 mm
Leaf position on plant
some leaf attachment points are above the midpoint of the stem
Perianth composition
there are bristles attached at the base of the achene
Fruit cross-section
the fruit is biconvex or elliptic (widest in the middle and tapering to both ends) in cross-section
Show All Characteristics
  • Flowers
    Anther length
    3–4 mm
    Floral bristle color
    the bristles are pale brown to brown
    Floral bristle number
    • 5-7
    • 8 or more
    Floral bristle relative length
    the bristles are longer than the achene
    Floral bristles
    the bristles are straight or slightly curved
    Floral scale hairs
    there are no hairs on the floral scales
    Floral scale length
    5–9.5 mm
    Floral scale nerves
    7 or more
    Floral scale shape
    the floral scales are lanceolate (widest below the middle, and tapering at both ends)
    Floral scale translucent
    the floral scales are opaque
    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 six or more bracts per inflorescence
    • 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 on one or more stems with no branches
    Inflorescence crowding
    the inflorescence is at least somewhat spread out, with at least one branch coming from the main stem
    Inflorescence position
    the inflorescence emerges from an axil, or most of its parts do so
    Inflorescence shape
    the aggregations within the inflorescence are at least somewhat flattened in cross-section
    Inflorescence type
    there are two or more flowers, spikes or flower clusters on a branched inflorescence
    Perianth composition
    there are bristles attached at the base of the achene
    Stamen number
    3
    Stigma number
    2
    Style division
    the top two thirds of the style is divided
    floral bristle barbs
    the bristles have tiny barbs on them
    plantlets budding at flower bases
    no
  • Fruits or seeds
    Achene tubercle relative width
    NA
    Achene tubercle width
    0 mm
    Capsule relative length
    NA
    Fruit cross-section
    the fruit is biconvex or elliptic (widest in the middle and tapering to both ends) in cross-section
    Fruit length
    2–4 mm
    Fruit type (general)
    the fruit is like a seed, and surrounded by scales
    Fruit type (specific)
    the fruit is an achene (dry, seed-like fruit) without a tubercle (a swelling or projection, usually of a different color or texture)
    Locules in capsule
    NA
    Seed length
    0 mm
    Seed tail relative length
    0 mm
    Seed tails
    NA
    Tubercle height
    0 mm
  • Growth form
    Lifespan
    the plant lives more than two years
    Rhizome thickness
    2–5 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
    there are no auricles on the leaf sheath
    Leaf blade cross-section
    the leaf blade is flat or rolled in at the edges
    Leaf blade length
    40–150 mm
    Leaf blade width
    3.5–8 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 do not have transverse septa
    Leaf sheath hairs
    the leaf sheathes are without hairs
    Pedicel length (Typha)
    0 mm
    Stem leaf blade ligules
    the plant has ligules at the leaf blade bases
    Stem leaf blades
    there are fully-developed leaves with leaf blades on the main stem
  • Place
    Habitat
    • aquatic
    • terrestrial
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • edges of wetlands
    • marshes
    • shores of rivers or lakes
  • Stem, shoot, branch
    Plant height
    20–100 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
    2–5 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.

Maine
unranked (S-rank: SNR)
Massachusetts
unranked (S-rank: SNR)

Native to North America?

Yes

Synonyms

  • Cyperus arundinaceus L.

Family

Cyperaceae

Genus

Dulichium

Notes on Subspecies and Varieties in New England

Our variety is Dulichium arundinaceum (L.) Britt. var. arundinaceum.

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Information from Dichotomous Key of Flora Novae Angliae

1.  Dulichium arundinaceum (L.) Britt. var. arundinaceum N

three-way sedge. Cyperus arundinaceus L. • CT, MA, ME, NH, RI, VT. River shores, lake shores, marshes, and other open wetlands.

Rhynchospora capitellata. This very rare intergeneric hybrid is known from only MA within New England. It has been known by the name Cyperus ×‌weatherbianus
Fern.; however, this name is incorrect as the plant is not part of the genus Cyperus 
 (see Raymond (1962) for discussion). Further, the name should not have been a genus 
but rather a nothogenus (formed by combining in a specific manner the generic 
names of the species involved). The plant is identified by its general resemblance to 
 R. capitellata with elongate, many-flowered (20–40 flowers) spikelets that resemble 
a species of Cyperus (except that the scales are spirally arranged and are terminated 
by a short awn). Most flowers are sterile and do not produce mature achenes, but 
those achenes that develop somewhat show a subulate tubercle at the apex of the achene body. The plant is further characterized by cespitose habit and terminal and axillary glomerules of spikelets (as in Rhynchospora) combined with flowers that 
lack perianth (as in Dulichium).