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Plant guide · Submerged plants

Large-leaf pondweed (Potamogeton amplifolius)

A native broad-leaf pondweed with large, wavy underwater leaves and oval floating leaves. Valued as fish habitat, and one of the plants grass carp usually leave alone.

Also called: bass weed, musky cabbage, broad-leaf pondweed

Oval floating leaves and broad submerged leaves of large-leaf pondweed in clear shallow water.
Large-leaf pondweed (USDA NRCS photo). Photo: Edward G. Voss, USDA NRCS (Northeast Wetland Flora, 1995), Public domain (source)

What it looks like

  • Large, wavy submerged leaves on stiff, firmly rooted stems that are seldom branched.
  • Oval floating leaves, alternating along the stem.
  • Grows in beds, with seed spikes sticking up above the water in summer.

Easily confused with

  • Curly-leaf pondweed (invasive): smaller wavy leaves with finely toothed edges.
  • Other broad-leaf pondweeds, which have heart-shaped floating leaves or leaves that clasp the stem.

Good and bad for your pond

  • Excellent habitat for panfish, bass and pike; fish feed on the insects living on it.
  • Can crowd swimming and dock areas.

Native or invasive?

Native

Native. Native (USDA PLANTS).

USDA PLANTS: POAM5 (lower 48 states: native)

Do grass carp eat it?

Grass carp usually leave it alone

Grass carp usually don't control large-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Checked Oct 4, 2026 · Source: Using Grass Carp to Control Aquatic Plants (updated May 19, 2025) This may be outdated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4, 2026 · Source: Filamentous Algae (updated May 19, 2025) and the companion Penn State plant fact sheets This may be outdated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

For small problem areas, rake or cut. Minnesota's DNR calls broad-leaf pondweeds important fish habitat and suggests leaving them where you can.

Biological options

Grass carp are not effective (see above).

Chemical options (permit first)

Minnesota's DNR notes these pondweeds are highly resistant to chemical control. 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.

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) 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.

Sources

Checked Oct 4, 2026