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Eleocharis obtusa — blunt spikesedge

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Facts

Blunt spikesedge is found on pond and river shores and in disturbed, wet areas. There are two varieties in New England, one of which is widespread and common, while the other is rare and restricted to Maine and New Hampshire.

Habitat

Anthropogenic (man-made or disturbed habitats), floodplain (river or stream floodplains), meadows and fields, shores of rivers or lakes

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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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
0 mm
Leaf blade cross-section
NA
Inflorescence position
the inflorescence is at the tip of the plant
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
0.9–1.3 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
Show all characteristics

  • Flowers

    Anther color (dry)
    the anthers range in color from white to tan or yellow to yellow-brown
    Anther length
    0.3–0.6 mm
    Floral bristle color
    the bristles are pale brown to brown
    Floral bristle number
    5-7
    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
    1.5–2.5 mm
    Floral scale nerves
    1
    Floral scale shape
    the floral scales are elliptic (widest in the middle and tapering toward each end)
    Floral scale translucent
    the floral scales are translucent
    Flower number per cluster
    more than 20
    Inflorescence bract angle
    NA
    Inflorescence bract number
    NA
    Inflorescence bract position (Sparganium)
    NA
    Inflorescence bracts
    NA
    Inflorescence branching
    the inflorescence is on one or more stems with no branches
    Inflorescence crowding
    • NA
    • 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 roughly circular (not flattened) in cross-section
    Inflorescence type
    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
    • yes

  • Fruits or seeds

    Achene beak length
    0 mm
    Achene surface texture
    the achene is smooth (it has no detectable texture)
    Achene tubercle relative width
    the tubercle is two thirds to about as wide as the achene
    Achene tubercle width
    0.4–0.8 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
    Fruit length
    0.9–1.3 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) with a tubercle (a swelling or projection, usually of a different color or texture) on it
    Locules in capsule
    NA
    Seed length
    0 mm
    Seed tail relative length
    0 mm
    Seed tails
    NA
    Tubercle height
    0.35–0.5 mm

  • Growth form

    Lifespan
    the plant lives only a single year or less
    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
    NA
    Leaf blade length
    0 mm
    Leaf blade width
    0 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
    NA
    Leaf sheath hairs
    the leaf sheathes are without hairs
    Pedicel length (Typha)
    0 mm
    Stem leaf blade ligules
    NA
    Stem leaf blades
    there are no leaves on the main stem, or there is a small tooth or tiny blade, or a leaf sheath with no blade
    Width of seed-producing inflorescence
    2–4 mm

  • Place

    Habitat
    • aquatic
    • terrestrial
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • man-made or disturbed habitats
    • meadows or fields
    • river or stream floodplains
    • shores of rivers or lakes

  • Stem, shoot, branch

    Plant height
    3–90 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
    0.2–2 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.

var. obtusa

Massachusetts
widespread (S-rank: S5)

var. peasei

New Hampshire
historical (S-rank: SH), endangered (code: E)

Subspecies and varieties

Eleocharis obtusa (Willd.) J.A. Schultes var. obtusa is known from CT, MA, ME, NH, RI, VT. E. obtusa var. peasei Svens. is known from ME, NH on sandy pond shores and river flats where water levels fluctuate, and is of conservation concern.

From Flora Novae Angliae dichotomous key

16.  Eleocharis obtusa (Willd.) J.A. Schultes NC

blunt spikesedge.  16a. Eleocharis obtusa (Willd.) J.A. Schultes var. jejuna Fern.; E. ovata (Roth) Roemer & J.A. Schultes var. obtusa (Willd.) Kükenth.; Scirpus obtusus Willd. • CT, MA, ME, NH, RI, VT. Low, wet areas, pond shores, river shores (these rarely tidal), meadows, disturbed wetlands.

1a.  Perianth bristles numbering 5–7 per achene, retrorsely barbellate, exceeding the combined length of the achene body and tubercle … 16a. E. obtusa var. obtusa

1b.  Perianth bristles lacking or, if present, numbering 2–4, smooth, and shorter than the achene body … 16b. E. obtusa var. peasei Svens.

Variety obtusa is known from CT, MA, ME, NH, RI, VT. Variety peasei is known from ME, NH 
 and is of conservation concern. It is usually found on sandy pond shores and tidal river flats 
(i.e., places where the water level might fluctuate tremendously daily or seasonally).

Native to North America?

Yes

Sometimes confused with

Eleocharis ovata:
tubercles 1/3 to 2/3 as wide as the achene body and styles usually bifid (vs. E. obtusa, with tubercles 2/3 to almost fully as wide as the achene body and styles usually trifid).
Eleocharis engelmannii:
tubercles 0.12-0.23 mm tall, styles usually bifid, and perianth bristles usually not exceeding the tubercle (vs. E. obtusa, with tubercles 0.2-0.4 mm tall, styles usually trifid, and perianth bristles usually exceeding the tubercle).

Synonyms

  • Eleocharis obtusa var. jejuna Fern.
  • Eleocharis ovata var. obtusa (Willd.) Kükenth.
  • Scirpus obtusus Willd.

Family

Cyperaceae

Genus

Eleocharis