Curly-Leaf Pondweed

Curly-leaf pondweed has become established in Lake Winnebago and in Becker Lake in Calumet County. The leaves are reddish-green, oblong, and about 3 inches long, with distinct finely toothed wavy edges. The stem of the plant is flat, reddish-brown and grows from 1 to 3 feet long. The plant usually drops to the lake bottom by early July.

Curly-leaf pondweed spreads through burr-like winter buds called turions. The plants also reproduce by seed, but this plays a small role compared to the vegetative reproduction through turions. New plants form under the ice in winter, making curly-leaf pondweed one of the first nuisance aquatic plants to emerge in the spring.

It becomes invasive in some areas because of its tolerance for low light and low water temperatures. These tolerances allow it to get a head start on and outcompete native plants in the spring. In mid-summer, when most aquatic plants are growing, curly-leaf pondweed plants are dying off. This is why it is frequently missed when monitoring for Eurasian water milfoil in mid to late summer.

Plant die-offs may result in a substantial loss of dissolved oxygen. Additionally, the decaying plants can increase nutrients which contribute to algal blooms. Curly-leaf pondweed forms surface mats that interfere with aquatic recreation.

Maintaining a healthy ecosystem with diverse native aquatic plants and animals as well as minimizing nutrient and pollutant inputs will deter invasions. Once introduced, curly-leaf pondweed spreads rapidly. Long-term management requires the reduction or elimination of turions to interrupt the lifecycle.

Department of Natural Resources permits are required for chemical treatments, mechanical treatments, and some manual treatments. For further information on chemical controls, visit the DNR website at www.dnr.state.wi.us/invasives/fact/curlyleaf_pondweed.htm

Manual/mechanical control efforts should be undertaken in the spring or early summer. Mechanical control includes raking, hand-cutting or harvesting vegetation. Raking and hand cutting remove plants at the sediment surface, and there is some evidence that early season cutting of pondweed can prevent turion production. Harvesting generally removes the top 5 feet of the plant. But be careful with your identification when you harvest. Becker Lake also has the native clasping leaf pondweed, an important part of our desired aquatic vegetation.

Curly-leaf pondweed can spread from turions and plant fragments, so it is important to clean all vegetation off boats and equipment before leaving water access. Remember to inspect all your equipment, remove attached plants or animals, drain all the water from your equipment.