Curly-Leaf Pondweed

Description

• Has a very distinctive appearance with crinkled leaves that alternate along the stem. Edges of leaves are also finely toothed.
• Common in ponds with hard, nutrient-rich water.
• Tolerant of low light conditions, often found in deeper water than many other aquatic plants.
• Plant dies in July and seeds drop to bottom sediment.
• Seeds germinate in fall, producing plants with winter foliage that remain green throughout the winter.
• In spring, long flower spikes often stick up above the water surface. As the pond water warms in the spring, the classic, wavy-leafed summer plants begin to grow until they die in July.

Value and Concern to the Pond

• Curly-leaf pondweed provides value to the pond because it grows through the winter and spring when most plants are absent from the pond. Thus, it provides a source of food and habitat during these times
• This invasive plant tends to crowd out native submerged plant species and can grow to nuisance levels.

Prevention

• Overabundant growth is a symptom of excessive nutrients (phosphorus and nitrogen) in the pond water.
• These nutrients may come from barnyards, crop fields, septic systems, lawns, and golf courses.
• Control of overabundant aquatic plants is best accomplished by reducing or redirecting nutrient sources from the pond by reducing fertilizer applications near the pond, maintaining septic systems properly, redirecting nutrient-rich runoff away from the pond, and maintaining vegetative buffer strips around the pond.
• Failure to address the underlying nutrient causes of aquatic plant growth will likely lead to a perpetual need to control overabundant plant growth

Physical Control

Physical control can be very effective on small ponds and is especially attractive because it also removes the nutrients.

• Can be removed by raking or cutting, especially in the spring before seeds appear above the water.
• Plants removed from the pond should be disposed of away from the pond edge so that wind or runoff cannot transport the plant or seeds back into the pond. This will also prevent decaying plant material from adding nutrients back into the pond.

Biological Controls

• Grass carp can be used to control curly-leaf pondweed because it is one of their preferred foods.
• Grass carp must be purchased from an approved hatchery after receiving a state permit.
• Consult the grass carp fact sheet available from your local Pennsylvania Fish and Boat Commission office or online at the Penn State Extension website.

Chemical Controls

There are numerous aquatic herbicides that are effective in controlling curly-leaf pondweed.  You can learn more about these herbicides and their use in Management of Aquatic Plants. Here are some tips to properly using an aquatic herbicide to control curly-leaf pondweed:

• Keep in mind that chemical control is often necessary every year or even multiple times during a year.
• Make sure that you positively identify the plant in your pond as curly-leaf pondweed before proceeding.
• Carefully measure the pond area and/or volume to determine the amount of herbicide needed. Consult the fact sheet entitled Pond Facts 4: Measuring Pond Area and Volume for more information.
• Before applying a herbicide to your pond, you must obtain a state permit from the Pennsylvania Department of Environmental Protection.  The two-page application form and instructions for this permit are online at Application for Use of an Algaecide, Herbicide, or Fish Control Chemical in Waters of the Commonwealth (PDF).
• Aquatic herbicides can be purchased from some home and farm supply stores, hardware stores, or various online suppliers. Costs can range from less than $100 to more than $1,000 to treat a one-acre pond.
• Follow the herbicide label carefully for specific instructions on when and how to apply the chemical.
• Herbicide treatments should be done early in the growing season before the plants cover a large portion of the pond. Treatment of severe infestations may cause a fish kill due to reduced dissolved oxygen.

Additional Resources

For further information and publications on pond management, visit the Penn State Extension website or contact your local extension office.

• View Aquatic Invasive Species in Pennsylvania
• Visit Pennsylvania Sea Grant to find a Curly-Leaf Pondweed fact sheet

Prepared by Bryan R. Swistock, senior extension associate and Heather Smiles, fisheries biologist, Pennsylvania Fish and Boat Commission.