Schoenoplectus pungens (Vahl) Palla

three-square bulrush

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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

There are three varieties of three-square bulrush in North America, but only this one occurs in New England, favoring lake and river shores, fens and marshes. The northern Paiute ground the seeds into flour for cooking.

Habitat

Brackish or salt marshes and flats, fens, floodplain (river or stream floodplains), fresh tidal marshes or flats, marshes, shores of rivers or lakes

Characteristics

Habitat
  • aquatic
  • wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Stem shape in cross-section
the stem is roughly triangular in cross-section
Leaf blade width
2–9 mm
Leaf blade cross-section
the leaf blade is flat or rolled in at the edges
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 on one or more stems with no branches
Fruit type (general)
the fruit is like a seed, and surrounded by scales
Fruit length
2–3.5 mm
Leaf position on plant
the attachment points of all the leaves are at or near the base of the plant
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
  • the fruit is lenticular (lens-shaped) in cross-section
  • the fruit is triangular to terete (circular) in cross-section
Show All Characteristics
  • Flowers
    Anther length
    2–3 mm
    Floral bristle color
    the bristles are pale brown to brown
    Floral bristle number
    • 1-4
    • 5-7
    • 8 or more
    Floral bristle relative length
    • the bristles are between one tenth as long as the achene, and equal in length to the achene
    • there are no bristles, or they are very tiny (less than one tenth as long as the achene)
    Floral bristles
    the bristles are straight or slightly curved
    Floral scale hairs
    the floral scales have hairs on them
    Floral scale length
    3.5–6 mm
    Floral scale nerves
    1
    Floral scale shape
    the floral scales are ovate (roughly egg-shaped)
    Floral scale translucent
    the floral scales are translucent
    Inflorescence bract angle
    the bracts are vertical or angled only slightly outwards
    Inflorescence bract number
    • there are two to five bracts per inflorescence
    • 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 on one or more stems with no branches
    Inflorescence crowding
    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
    • there is one spike or raceme at the tip of the stem
    Perianth composition
    there are bristles attached at the base of the achene
    Stamen number
    3
    Stigma number
    • 2
    • 3
    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 beak length
    0.1–0.5 mm
    Achene surface texture
    the achene is smooth (it has no detectable texture)
    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
    • the fruit is lenticular (lens-shaped) in cross-section
    • the fruit is triangular to terete (circular) in cross-section
    Fruit length
    2–3.5 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
    1–6 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
    50–750 mm
    Leaf blade width
    2–9 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
    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
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • brackish or salt marshes and flats
    • fens
    • fresh tidal marshes or flats
    • marshes
    • river or stream floodplains
    • shores of rivers or lakes
  • Stem, shoot, branch
    Plant height
    10–200 cm
    Stem shape in cross-section
    the stem is roughly triangular in cross-section
    Stem texture near tip
    the stem feels smooth near the tip
    Stem thickness at midpoint
    1–6 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

Sometimes Confused With

Schoenoplectus americanus:
uppermost leaf with a short blade that is shorter than its associated sheath and stems with conspicuosly concave sides (vs. S. pungens, with the uppermost leaf with a well developed blade that is several times longer than its associated sheath and stems with flat to shallowly concave sides).

Synonyms

  • Scirpus pungens Vahl.

Family

Cyperaceae

Notes on Subspecies and Varieties in New England

Our variety is Schoenoplectus pungens (Vahl) Palla var. pungens.

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Information from Dichotomous Key of Flora Novae Angliae

6.  Schoenoplectus pungens (Vahl) Palla var. pungens N

three-square bulrush. Scirpus pungens Vahl • CT, MA, ME, NH, RI, VT. Lake shores, fresh to brackish river shores, lakeside fens, marshes.

2×6. Schoenoplectus americanus × Schoenoplectus pungens Schoenoplectus ×‌contortus (Eames) S.G. Sm. is a rare hybrid in New England, and one that has been tentatively identified for some states where one of the parents ( S. americanus) has not been documented (e.g., ME, VT). The hybrid is morphologically intermediate between the parents.