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Cyperus bipartitus — shining flatsedge

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Facts

Shining flatsedge is found in moist to wet shorelines throughout New England; although native to most of our area, some populations in Rhode Island may have been introduced. The seeds produced by the flowers inside copper-colored scales may be eaten by some birds.

Habitat

Shores of rivers or lakes, wetland margins (edges of wetlands)

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
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
  • the stem is round or oval in cross-section
Leaf blade width
1–2 mm
Leaf blade cross-section
the leaf blade is flat or rolled in at the edges
Inflorescence position
the inflorescence is at the tip of the plant
Inflorescence branching
the inflorescence is branched
Fruit type (general)
the fruit is like a seed, and surrounded by scales
Fruit length
1–1.5 mm
Leaf position on plant
the attachment points of all the leaves are at or near the base of the plant
Perianth composition
there is no perianth on the plant
Fruit cross-section
the fruit is lenticular (lens-shaped) in cross-section
Show all characteristics

  • Flowers

    Anther length
    0.4–0.5 mm
    Floral bristle color
    NA
    Floral bristle number
    0
    Floral bristle relative length
    NA
    Floral bristles
    NA
    Floral scale hairs
    there are no hairs on the floral scales
    Floral scale length
    1.9–2.7 mm
    Floral scale nerves
    2-5
    Floral scale shape
    • the floral scales are oblong (rectangular but with rounded ends)
    • the floral scales are ovate (roughly egg-shaped)
    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 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
    • the inflorescence is crowded together in one tight cluster
    Inflorescence position
    the inflorescence is at the tip of the plant
    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 is no perianth on the plant
    Stamen number
    • 2
    • 3
    Stigma number
    2
    Style division
    the top two thirds of the style is divided
    floral bristle barbs
    NA
    plantlets budding at flower bases
    no

  • Fruits or seeds

    Achene beak length
    0 mm
    Achene surface texture
    the achene has very tiny pits or depressions on it
    Achene tubercle relative width
    NA
    Achene tubercle width
    0 mm
    Capsule relative length
    NA
    Fruit cross-section
    the fruit is lenticular (lens-shaped) in cross-section
    Fruit length
    1–1.5 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 only a single year or less
    Rhizome thickness
    0 mm
    Underground organs
    there are only slender roots on the plant

  • 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
    10–80 mm
    Leaf blade width
    1–2 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
    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
    7–14 mm

  • Place

    Habitat
    wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • edges of wetlands
    • shores of rivers or lakes

  • Stem, shoot, branch

    Plant height
    3–30 cm
    Stem shape in cross-section
    • the stem is roughly triangular in cross-section
    • the stem is round or oval in cross-section
    Stem texture near tip
    the stem feels smooth near the tip

Wetland status

Usually occurs in wetlands, but occasionally in non-wetlands. (Wetland indicator code: FACW)

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)

From Flora Novae Angliae dichotomous key

2.  Cyperus bipartitus Torr. N

shining flatsedge. Cyperus rivularis Kunth; Pycreus rivularis (Kunth) Palla • CT, MA, ME, NH, RI, VT. Moist to wet, usually sandy, shorelines.

Native to North America?

Yes

Sometimes confused with

Cyperus diandrus:
floral scales with anthocyanic pigments most prominent along medial and apical margin and along upper edges of midribs, with a conspicuous pale area between the midrib and margin, and style divided nearly to its base (vs. C. bipartitus, with floral scales with anthocyanic pigments most prominent in basal and medial portion, fading toward apex, the pigmented region not outlining a conspicuous pale region on each side of the scale, and style connate in the basal 1/3).
Cyperus flavescens:
achenes broad-obovate to nearly suborbicular in outline, minutely marked with elongate, superficial cells and irregular, pale transverse lines at maturity, and floral scales broad-ovate (vs. C. bipartitus, with achenes narrow-obovate to oblong in outline, unmarked, and floral scales narrow-oblong to ovate).

Synonyms

  • Cyperus rivularis Kunth
  • Pycreus rivularis (Kunth) Palla

Family

Cyperaceae

Genus

Cyperus