Curly-leaf pondweed is a rooted, submersed aquatic plant. Its coloration varies from olive-green to reddish-brown.
Leaves and Stem
Wavy, lasagna-like leaves grow approximately a half-inch wide and two to three inches long. Leaves have an obvious mid-vein, “toothed” or serrated edges and blunt tips. Leaves are arranged alternately, are directly attached to the stem, and become denser toward the end of the stem. The main stem can be various colors including white, green, brown, and red, and tends to brach multiple times near the top of the plant. The plant may mat at the surface, but does not have true floating leaves.
The flower stalk grows up above the water surface, typically in June. It grows to about one inch tall and appears reddish-brown in the water, but is actually green when examined closely.
Reproductive structures are called turions. They are brown, typically a half-inch in size and look like sharp small pinecones. It can also reproduce via seed, but seeds play a small role in reproduction.
The root structure comprises of a thick, pale yellow slender rhizome (an underground stem that sends out roots and shoots from its nodes). Many stems can be connected by one rhizome.
Curly-leaf pondweed generally grows from the shore to depths of 15 feet of water, and can grow up to 15 feet tall. It tolerates low water clarity and will readily invade disturbed areas. Curly-leaf can be distinguished from native pondweeds by its unique life cycle. Turions sprout in the fall, and it is generally the first pondweed to come up in the spring. It typically flowers, fruits, and produces turions in June before dying back in mid-summer.
Origin and Spread
Curly-leaf pondweed is native to Eurasia, Africa, and Australia. It was likely introduced when common carp were intentionally introduced into Midwest waters as a game fish in the 1880s. The species was likely spread through the movement of watercraft and water-related equipment. It was first noted in Minnesota around 1910.
Don't be fooled by these look-alikes
Curly-leaf pondweed looks similar to many native beneficial pondweeds found in Minnesota lakes and rivers, but can be distinguished based on its serrated leaf edges.
- Broad-leaf pondweeds (native)
- Clasping-leaf pondweed (native)
- White-stem pondweed (native)
- Narrow-leaf pondweeds (native)
Curly-leaf Pondweed (Potamogeton crispus) is a prohibited invasive species in Minnesota, which means it is unlawful (a misdemeanor) to possess, import, purchase, transport or introduce this species except under a permit for disposal, control, research or education.
Threat to Minnesota Waters
Curly-leaf pondweed causes recreational, economic and ecological damage—changing how residents and visitors use and enjoy Minnesota waters.
Curl-leaf pondweed impacts:
- Dense mats at the water’s surface inhibit water recreationists.
- Overtakes habitat and outcompetes native aquatic plants, potentially lowering diversity.
- Provides unsuitable shelter, food, and nesting habitat for native animals.
- Midsummer die-offs can litter the shoreline with dead plants.
What you should do
People spread curly-leaf pondweed primarily through the movement of water-related equipment. Plant fragments and turions can get stuck on trailers, motors, docks, boat lifts, swim rafts and inside watercraft (boats, canoes and kayaks). Turions, which may be hidden in mud and debris, can stick to anchors as well as scuba, fishing, and hunting gear.
Whether or not a lake is listed as infested, Minnesota law requires water recreationists to:
- Clean watercraft of all aquatic plants and prohibited invasive species.
- Drain all water by removing drain plugs and keeping them out during transport.
- Dispose of unwanted bait in the trash.
- Dry docks, lifts, swim rafts and other equipment for at least 21 days before placing equipment into another water body.
Management of invasive aquatic plants involving either mechanical removal of plants or application of herbicides to public waters requires a permit from the DNR. Talk to a DNR specialist for more information.
Mechanical control can be done by cutting or pulling the plant by hand or with equipment such as rakes or cutting blades.
Herbicide control can be done using an endothall herbicide.