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Eleocharis equisetoides — horsetail spikesedge

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Facts

Horsetail spikesedge is very rare in New England, with a few populations known from lake shores in Connecticut, Massachusetts and Rhode Island; indeed, it is listed as rare in many states where it occurs. The plant actually resembles a horsetail, with a rounded stem that is divided into sections by septa and is topped by a long, cylindrical spike reminiscent of the cone of a horsetail.

Habitat

Lacustrine (in lakes or ponds), 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
  • wetlands
New England state
  • Connecticut
  • Massachusetts
  • Rhode Island
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
1.8–2.3 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
  • there is no perianth on the plant
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
    2.6–3.2 mm
    Floral bristle color
    the bristles are slightly or strongly colored with reddish 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
    Floral bristles
    the bristles are straight or slightly curved
    Floral scale hairs
    there are no hairs on the floral scales
    Floral scale length
    4.8–7 mm
    Floral scale nerves
    7 or more
    Floral scale shape
    • the floral scales are oblong (rectangular but with rounded ends)
    • the floral scales are obovate (roughly egg-shaped, but with the widest part above the middle)
    Floral scale translucent
    the floral scales are opaque
    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
    • there is no perianth on the plant
    Stamen number
    • 1
    • 2
    • 3
    Stigma number
    • 2
    • 3
    Style division
    the top two thirds of the style is divided
    plantlets budding at flower bases
    no
  • Fruits or seeds

    Achene beak length
    0 mm
    Achene surface texture
    the achene has stripes or ridges that run from end to end
    Achene tubercle relative width
    the tubercle is one half or less as wide as the achene
    Achene tubercle width
    0.5–0.7 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
    1.8–2.3 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
    0.6–1.1 mm
  • Growth form

    Lifespan
    the plant lives more than two years
    Rhizome thickness
    2–4 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
    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
    4–8 mm
  • Place

    Habitat
    • aquatic
    • wetlands
    New England state
    • Connecticut
    • Massachusetts
    • Rhode Island
    Specific habitat
    • in lakes or ponds
    • shores of rivers or lakes
  • Stem, shoot, branch

    Plant height
    15–60 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
    5–8.4 mm

Wetland status

Occurs only in wetlands. (Wetland indicator code: OBL)

In New England

Distribution

Connecticut
present
Maine
absent
Massachusetts
present
New Hampshire
absent
Rhode Island
present
Vermont
absent

Conservation status

Exact status definitions can vary from state to state. For details, please check with your state.

Connecticut
extremely rare (S-rank: S1), endangered (code: E)
Massachusetts
historical (S-rank: SH)
Rhode Island
rare (S-rank: S2), concern (code: C)

From Flora Novae Angliae dichotomous key

8.  Eleocharis equisetoides (Ell.) Torr. NC

horsetail spikesedge. Scirpus equisetoides Ell. • CT, MA, RI. Lake shores, often growing in standing water.

Native to North America?

Yes

Sometimes confused with

Eleocharis quadrangulata:
reproductive stems +/- square in cross-section, lacking transverse septa (vs. E. equisetoides, with reproductive stems +/- circular in cross-section, with transverse septa).

Synonyms

  • Scirpus equisetoides Ell.

Family

Cyperaceae

Genus

Eleocharis