Carex acutiformis — lesser pond sedge
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Facts
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)
New England distribution
Adapted from BONAP data
Native: indigenous.
Non-native: introduced (intentionally or unintentionally); has become naturalized.
County documented: documented to exist in the county by evidence (herbarium specimen, photograph). Also covers those considered historical (not seen in 20 years).
State documented: documented to exist in the state, but not documented to a county within the state. Also covers those considered historical (not seen in 20 years).
Note: when native and non-native populations both exist in a county, only native status is shown on the map.
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enlargeCharacteristics
- 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
-
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)
In New England
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)
From Flora Novae Angliae dichotomous key
117. Carex acutiformis Ehrh. E
lesser pond sedge. CT, MA. Graminoid meadows, marsh edges, lake shores, and wet fields.
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).