Curly-Leaf Pondweed in Wisconsin
As of September 2026: Curly-leaf pondweed is classified as a restricted invasive species under Wis. Admin. Code NR 40. This page summarizes current DNR guidance.
Curly-leaf pondweed is the invasive plant that shows up early and leaves early. It's one of the first plants to grow each spring, sometimes under ice, and it usually dies back by midsummer, which changes both when it's a problem and when removal actually makes sense.
How to identify it
Curly-leaf pondweed
invasivePotamogeton crispus
- Submersed leaves 0.5 to 3.5 in long, alternating along the stem
- Reddish-green, wavy, finely serrated edges, like lasagna noodles
- Reddish-brown stem, 1 to 3 feet
Restricted invasive. Hand removal is exempt; mechanical harvesting or an NR 107 herbicide are the other options.
Identification only. Permit rules are on the DNR permit page.
Look for reddish-green, wavy leaves with finely serrated edges, arranged alternately along a reddish-brown stem, often described as looking like lasagna noodles underwater. It's a submersed plant, rooted in the bottom, not a floating mat.
Why it matters
Because curly-leaf pondweed grows before most native plants wake up, it can dominate a shallow bay in early spring, crowding boat lanes and swim areas right when lake season starts. Then it dies back and decomposes by early-to-mid summer, which can trigger a nutrient release and an algae bloom right after, so the plant's biggest impact isn't always visible when people first notice it.
It also produces turions, small bud-like structures that drop to the lake bottom and sprout the following year, which is part of why cutting the visible plant in June doesn't necessarily reduce next year's growth.
Removal timing and options
- Hand-pulling. Exempt statewide as invasive-species removal, with the same practical catch as any rooted plant: get the root, not just the stem, and get material out of the water afterward.
- Herbicide. Because the plant grows early, many lake districts time an NR 107 treatment for spring, before native plants have emerged, which can improve selectivity against curly-leaf specifically. That timing decision is a management-plan question, not a single-owner one.
- Mechanical harvesting. Useful for open beds ahead of the natural die-back, though it needs an NR 109 permit and doesn't address the turions already on the bottom.
See seasonal timing for lake weed removal for how curly-leaf's early growth cycle affects the calendar for other plants too.
Permit path
Hand removal of curly-leaf pondweed is exempt under the same invasive-species allowance that covers Eurasian watermilfoil, so a shoreline owner can pull confirmed curly-leaf at any width without a permit. Herbicide and mechanical harvesting both require a permit, NR 107 for the chemical route and NR 109 for the mechanical one. Full logic is on the DNR permit rules page.
Confirm identification first
Curly-leaf pondweed's wavy, serrated leaf is fairly distinct, but a handful of native pondweeds share the same submersed, leafy look from a distance. If you're not confident, compare against Eurasian watermilfoil, the other common early-season invasive, and see removal methods compared once you've confirmed what you're looking at.