Carex acutiformis Ehrh.

lesser pond sedge

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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

Lesser pond sedge is an occasional introduction from Eurasia that can form large colonies. This species was studied to determine the consequences of having flowering stems that are triangular in cross-section, versus the much stronger round, hollow stems of grasses. Triangular stems turn out to be better at twisting when they bend in the wind, so that male parts of the flowering stem are always held downwind from female parts, minimizing self-pollination.

Habitat

Marshes, meadows and fields, shores of rivers or lakes, wetland margins (edges of wetlands)

Characteristics

Habitat
wetlands
New England state
  • Connecticut
  • Massachusetts
stem leaf blade width
5–8 mm
Lowest bract sheath
the lowest bract has no sheath (or a very short sheath up to four millimeters in length)
Spike on stalk
  • the lowest spike on the plant has a peduncle
  • the lowest spike on the plant is not borne on a peduncle
Top spike
the uppermost spike contains only staminate flowers
Perigynium hairs
the perigynium has no hairs
Perigynium length
3–4.5 mm
Leaf sheath color
  • the leaf sheath has no pink, red or purple tinting
  • the leaf sheath is tinted pink, red or purple
Leaf blade texture
the leaf blade is smooth and hairless, or rough and sandpapery
Perigynium beak teeth
  • the perigynium beak is divided at the top into two teeth
  • the perigynium beak is not divided at the tip into two teeth, or the teeth are very tiny
Show All Characteristics
  • Flowers
    Bumps on fruit
    there are no papillae on the perigynium surface
    Inflorescence length
    150–350 mm
    Length of scale
    • the scale is nearly as long as, or longer than, the perigynium
    • the scale is shorter than the perigynium
    Lowest spike length
    30–80 mm
    Lowest spike stalk length
    At least 0 mm
    Lowest spike width
    Up to 7 mm
    Perigynium beak
    the perigynium has a beak
    Perigynium beak length
    0.3–0.6 mm
    Perigynium beak orientation
    the beak of the perigynium is straight, and in line with the perigynium
    Perigynium beak serrations
    the perigynium beak has no serrations
    Perigynium beak teeth
    • the perigynium beak is divided at the top into two teeth
    • the perigynium beak is not divided at the tip into two teeth, or the teeth are very tiny
    Perigynium beak teeth length
    Up to 0.2 mm
    Perigynium color
    glaucous (with a whitish bloom)
    Perigynium cross-section
    • the perigynium is relatively flat in cross-section
    • the perigynium is trigonous (triangular) in cross-section
    Perigynium hairs
    the perigynium has no hairs
    Perigynium length
    3–4.5 mm
    Perigynium nerve number
    12–18
    Perigynium nerve texture
    the nerves on the perigynium are raised, even after drying the perigynium
    Perigynium nerves lower side
    6–9
    Perigynium nerves upper side
    6–9
    Perigynium orientation
    the perigynia are oriented vertically or pressed against the axis or adjacent perigynia
    Perigynium puffy
    the achene is tightly enclosed by the perigynium
    Perigynium shape
    the perigynium body is ovate (egg-shaped)
    Perigynium width
    1.4–2.1 mm
    Perigynium winged
    the perigynium has no wings
    Pollen- and seed-producing spikes
    some of the spikes produce perigynia
    Pollen-producing spike number
    1–3
    Scale awn
    the carpellate scale has an awn on it
    Scale awn texture
    the carpellate scale awn has tiny teeth
    Scale color
    • brown
    • purple to black
    Scale tip
    • the carpellate scale tip is acuminate (tapered to a narrow point)
    • the carpellate scale tip is acute (has a sharp point)
    Spike on stalk
    • the lowest spike on the plant has a peduncle
    • the lowest spike on the plant is not borne on a peduncle
    Spike orientation
    the spikes are oriented vertically or pressed against the axis
    Spikes per stem
    2-15
    Stigma branching
    the stigmas have three branches
    Top spike
    the uppermost spike contains only staminate flowers
  • Fruits or seeds
    Achene dimples
    the achene has no folds or dimples
    Style persistence
    the style stays on the mature achenes
  • Growth form
    Rhizomes
    there are long rhizomes present
  • Leaves
    Leaf arrangement
    the leaves are all produced from the base of the plant
    Leaf blade cross-section
    the leaf blade is flat or M-shaped, with two prominent side-veins
    Leaf blade texture
    the leaf blade is smooth and hairless, or rough and sandpapery
    Leaf bumps
    the upper surface of the leaf blade does not have papillae
    Leaf sheath bumps
    there are no papillae at the top edge of the leaf sheath
    Leaf sheath color
    • the leaf sheath has no pink, red or purple tinting
    • the leaf sheath is tinted pink, red or purple
    Leaf sheath dots
    there are red dots on the translucent tissues of the leaf sheathes
    Leaf sheath folds
    there are no corrugations on the leaf sheath
    Leaf sheath texture
    the leaf sheath feels smooth, and has no hairs
    Ligule length
    5–14 mm
    Lowest bract sheath
    the lowest bract has no sheath (or a very short sheath up to four millimeters in length)
    Lowest leaf blade width
    5–8 mm
    Lowest leaf sheath texture
    the leaf sheath feels smooth (it may have soft hairs)
    stem leaf blade width
    5–8 mm
  • Place
    Habitat
    wetlands
    New England state
    • Connecticut
    • Massachusetts
    Specific habitat
    • edges of wetlands
    • marshes
    • meadows or fields
    • shores of rivers or lakes
  • Stem, shoot, branch
    Plant height
    15–130 cm
    Relative stem height
    • the main stem is equal to or shorter than the leaves
    • the main stem is taller than the leaves
    Stem cross-section
    the main stem is roughly triangular in cross-section
    Stem spacing
    the stems grow singly or a few together (they may form diffuse colonies)

Wetland Status

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

New England Distribution and Conservation Status

Distribution

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

Conservation Status

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

Massachusetts
not applicable (S-rank: SNA)

Native to North America?

No

Sometimes Confused With

Carex striata:
perigynia 3.9-7 mm long, not glaucous, with a beak 0.5-1.3 mm long that is terminated by 2 distinct teeth mostly 0.2-0.6 mm long (vs. C. acutiformis, with perigynia 3-4.5 mm long, glaucous, with a beak 0.3-0.6 mm long that is weakly bidentate with apical teeth up to 0.2 mm long).

Family

Cyperaceae

Genus

Carex

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Information from Dichotomous Key of Flora Novae Angliae

117.  Carex acutiformis Ehrh. E

lesser pond sedge. CT, MA. Graminoid meadows, marsh edges, lake shores, and wet fields.