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Plant guide · Submerged plants

Curly-leaf pondweed (Potamogeton crispus)

An invasive pondweed with crinkled, finely toothed leaves. It grows through winter, peaks in spring and dies back in July after setting seed, the opposite of most pond plants.

Also called: curly pondweed

Close view of curly-leaf pondweed stems with wavy, finely toothed reddish-green leaves.
Curly-leaf pondweed, showing its wavy, toothed leaves. Photo: Krzysztof Ziarnek, Kenraiz, CC BY-SA 4.0 (source)

What it looks like

  • Wavy, crinkled leaves with finely toothed edges, alternating along the stem.
  • DCNR notes it is the only pondweed in North America with serrated leaves, which makes it easy to identify.
  • Grows in fall and winter, even under ice; flower spikes poke above the water in spring.
  • Dies back in July after dropping seeds and buds.

Easily confused with

  • Native pondweeds, including large-leaf pondweed: no teeth on the leaf edges.

Good and bad for your pond

  • Gives fish and wildlife food and cover in winter and spring, when little else grows.
  • Invasive: crowds out native underwater plants and reaches nuisance levels.

Native or invasive?

Invasive in Pennsylvania

Invasive. A severe-threat invasive on DCNR's list; introduced to North America (USDA PLANTS).

USDA PLANTS: POCR3 (lower 48 states: introduced)

Do grass carp eat it?

Grass carp eat it

PFBC lists pondweeds among grass carp foods, and Penn State says grass carp can control curly-leaf pondweed. Grass carp prefer submerged plants like pondweeds, elodea and coontail; they rarely control algae mats or lilies.

Checked Oct 4, 2026 · Source: Using Grass Carp to Control Aquatic Plants (updated May 19, 2025) This may be outdated

Control options

Prevention first

Penn State Extension's advice for every nuisance plant and algae problem starts with nutrients: overgrowth is a symptom of excess phosphorus and nitrogen from sources such as barnyards, crop fields, septic systems, lawns and golf courses. Cutting fertilizer near the pond, maintaining septic systems, diverting nutrient-rich runoff and keeping a vegetated buffer strip are the long-term fixes; without them, control becomes a yearly chore.

Checked Oct 4, 2026 · Source: Filamentous Algae (updated May 19, 2025) and the companion Penn State plant fact sheets This may be outdated

Remove it by hand or machine

Rake or cut it in spring, before the seeds appear above the water, and dispose of it away from the pond edge. DCNR warns the plant is brittle: avoid leaving fragments.

Biological options

Grass carp, with a PFBC permit: PFBC grass carp permit needed for each waterbody before buying or stocking; $85 fee, returned if denied.

Checked Oct 4, 2026 · Source: 58 Pa. Code § 71a.10, Triploid grass carp This may be outdated

Chemical options (permit first)

Any herbicide or algaecide in a pond needs a joint DEP/PFBC Chapter 91 permit first, at any amount. Only products registered with the U.S. Environmental Protection Agency and with the Pennsylvania Department of Agriculture, and labeled specifically for aquatic use, can be listed on the Chapter 91 permit application. Treat in sections, early in the season: decaying plants can strip oxygen and kill fish.

Checked Oct 4, 2026 · Sources: Water Quality Permitting for Pesticide Applications in Pennsylvania: FAQ (rev. Feb 21, 2025), FAQ #2, #3, #8, #10, #11, #28, #29; Permit Requirement for Use of an Aquatic Herbicide in Ponds (updated Sep 8, 2025); Pond Management (FAQ: controlling submerged vegetation) This may be outdated

Follow the product label; the label is the law. A Chapter 91 permit is required before any herbicide or algaecide goes in a pond (see fact). Consider a licensed applicator.

Report it

Report a suspected aquatic invasive species, such as hydrilla or European water chestnut, to the Pennsylvania Fish and Boat Commission with its online form or the Pennsylvania Invasive Species Reporting hotline (1-833-INVASIV), or through PA iMapInvasives. A photo and the exact location help staff confirm it.

Checked Oct 4, 2026 · Source: Report Aquatic Invasive Species (AIS) This may be outdated

PFBC: Report aquatic invasive species PA iMapInvasives

Sources

Checked Oct 4, 2026