Eleocharis intermedia J.A. Schultes

mudflat spikesedge

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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

Mudflat spikesedge inhabits sandy or muddy streamsides and pond edges, and river sand bars. It is often found in areas with high-pH bedrock. It is considered "threatened" in Massachusetts, where it reaches the northern edge of its range. It is a small, annual plant that forms mats of densely tufted plants with wiry stems. The yellow-brown achenes ripen in mid-to-late summer, and are topped by a "dunce-cap" -- a long, cylindrical tubercle.

Habitat

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

Characteristics

Habitat
  • aquatic
  • wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • 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
1.2–1.5 mm
Leaf position on plant
the attachment points of all the leaves are at or near the base of the plant
Perianth composition
there are bristles attached at the base of the achene
Fruit 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
    0.2–0.5 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
    • 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
    there are no hairs on the floral scales
    Floral scale length
    1.7–2.5 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
    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
    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 mm
    Achene surface texture
    the achene has very tiny pits or depressions on it
    Achene tubercle relative width
    the tubercle is one half or less as wide as the achene
    Achene tubercle width
    0.1–0.25 mm
    Capsule relative length
    NA
    Fruit cross-section
    • the fruit is lenticular (lens-shaped) in cross-section
    • the fruit is triangular to terete (circular) in cross-section
    Fruit length
    1.2–1.5 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) 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
    0.3–0.4 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
    NA
    Leaf blade length
    0–1 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
    1–2 mm
  • Place
    Habitat
    • aquatic
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Vermont
    Specific habitat
    • bogs
    • man-made or disturbed habitats
    • river or stream floodplains
    • shores of rivers or lakes
  • Stem, shoot, branch
    Plant height
    4–40 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
    0.2–0.5 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
absent
Vermont
present

Conservation Status

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

Connecticut
unrankable (S-rank: SU)
Maine
rare (S-rank: S2)
Massachusetts
rare (S-rank: S2), threatened (code: T)
New Hampshire
historical (S-rank: SH), endangered (code: E)
Vermont
uncommon (S-rank: S3)

Native to North America?

Yes

Sometimes Confused With

Eleocharis microcarpa:
achenes pale, nearly white, 0.5-1 mm long, and floral scales 1-1.5 mm long (vs. E. intermedia, with achenes green to brown-green, 1.2-1.5 mm long, and floral scales 1.7-2.5 mm long).
Eleocharis flavescens:
styles usually bifid, achenes biconvex, and leaf sheaths prolonged at summit into a white, scarious tip (vs. E. intermedia, with styles trifid, achenes compressed-trigonous, and leaf sheaths variable at apex, but without a prolonged white, scarious apex).

Family

Cyperaceae

Genus

Eleocharis

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Information from Dichotomous Key of Flora Novae Angliae

12.  Eleocharis intermedia J.A. Schultes N

mudflat spikesedge. CT, MA, ME, NH, VT. Sandy, muddy, or boggy margins of streams and ponds, often associated with areas of high-pH bedrock or till, also frequent in areas of disturbance (e.g., accretion bars along rivers).