Underwater plant
Curly-leaf Pondweed
Potamogeton crispus
These illustrations are AI-generated, not photographs, and are not to scale. They show what to look for; they are not a substitute for an expert identification.
How to identify it
Size: Leaves about 2 to 4 inches long.
- Leaves with wavy, crinkled edges, like the edge of a lasagna noodle.
- Tiny teeth along the leaf edges. Look closely or run a fingertip along one.
- Olive-green to reddish-brown color.
- Leaves spaced one at a time along the stem, alternating sides.
- In late spring it forms hard, bur-like buds called turions that sink and sprout later.
Don’t confuse it with
Native clasping-leaf pondweed has wavy leaf edges too, so waviness does not tell them apart. Its edges have no teeth — run a fingertip along one — and its leaf bases wrap right around the stem.
Where it came from
Native to Europe, Asia, Africa and Australia.
Present in North America since at least the mid-1800s. It spreads by stem pieces and turions carried on boats and gear.
Earliest dated Michigan record: 1926, Pigeon Lake, Ottawa County. This is the oldest dated record in the USGS non-native species database, not necessarily when it first arrived.
Why it matters
It starts growing very early, even under ice, and can form thick mats in spring before native plants get going. It dies back in early summer, and the rotting plants can release nutrients that feed algae blooms.
Michigan law
Restricted under Part 413 of Michigan's Natural Resources and Environmental Protection Act. It is illegal to possess, introduce, import, sell or offer to sell it as a live organism, except in the limited cases the law allows. The state uses “restricted” for species already established in Michigan. The state’s page on this species.
If you find it
- Don’t move it. Michigan law requires boaters to remove all aquatic plants from boats, equipment and trailers before launching. Before trailering, you must pull all drain plugs, drain live wells and bilges, and make sure the boat and trailer are free of aquatic plants and animals. What the law requires
- Never release bait. Releasing baitfish into Michigan waters is illegal. Put unused bait in the trash, never in the water.
- Report it. Take a photo, note where you saw it, and report it to the Midwest Invasive Species Information Network (MISIN) or through Michigan’s invasive species program. Experts there can confirm what you found.
- Ask before removing or treating. Treating a lake with herbicides or other chemicals needs a state permit, and some removal work does too. Start with the state’s Aquatic Nuisance Control program before taking action.
Michigan lakes where it has been recorded
44 Michigan lakes on this site have a record of this species.
Barry
Branch
Clinton
Genesee
Gogebic
Ingham
Iron
Jackson
Kent
Lapeer
Leelanau
Lenawee
Livingston
Lake Chemung, Thompson Lake, Whitewood Lakes, Whitmore Lake, Zukey Lake
Manistee
Mason
Newaygo
Oceana
Ottawa
St. Joseph
Van Buren
Washtenaw
Wayne
A lake that is not listed may still have it. Records exist only where someone found the species and reported it, so “not recorded” does not mean “not present.”
Lake records: Midwest Glacial Lakes Partnership Conservation Planner; underlying records from the USGS Nonindigenous Aquatic Species database.
Sources
- Michigan Invasive Species Program: Curly-leaf pondweed
- Midwest Invasive Species Information Network: Curly-leaf pondweed
- Michigan Compiled Laws, section 324.41302 (prohibited and restricted species)
Earliest dated record: USGS Nonindigenous Aquatic Species database.