Clemson Extension Forestry and Wildlife

Managing Aquatic Weeds in Ponds

Properly managed pond. Photo Credit: Lance Beecher, Clemson Extension.
Properly managed pond. Photo Credit: Lance Beecher, Clemson Extension.

Ponds are a unique addition to any landscape and offer many benefits to the pond owner. These ponds are typically intended to provide one or more common goals: visual amenities, fishing, swimming, and wildlife or bird watching. While a pond can frequently support more than one goal, maintenance may differ depending on use. Like other parts of the terrestrial landscape, ponds should be considered a vital part of the landscape and require routine maintenance. One such maintenance requirement is managing aquatic vegetation, and if not routinely controlled can get out of hand quickly and can be costly in the long run.

The first step in adequately managing aquatic plants is carefully identifying and understanding the ecology and importance of the plant in the ecosystem. Most plants are essential to the ecosystem and play a vital role in productivity; however, some may enter the system and become abundant rather quickly and outproduce wanted plants and become unsightly. Aquatic plants that cause weed problems are split into algae, floating, emergent, and submerged plants.

  • Algae are the most popular group of plants found in ponds. Their shape and size differ from microscopic single- or multiple-celled to branched plants that resemble submerged aquatic plants.
  • Floating plants can float on the water’s surface, and their exposed roots can obtain nutrients from water rather than soil.
  • Emergent plants are rooted in the bottom of the pond. They have stems, leaves, and flowers that extend above the water surface. They primarily occur on the shoreline and in shallow water around the pond’s edge.
  • Submerged aquatic plants grow primarily under and up to the water surface. Most of these plants have flowers and seed heads that extend above the water’s surface.

Now that we know what types of plants are out there, we need to explore some management ideas to control aquatic plants. One easy way to manage a pond is to contact a local pond management company and set up a monthly management plan, and troubles are few. The company will set up a plant control plan and perform necessary chemical applications to control the growth of plants. They may offer other alternatives that may benefit the pond’s long-term enjoyment.

Now, if you are a DIY person and what to build some strategies on your own, here are some preventive measures to help. Management techniques can be based on mechanical, chemical, and biological means to help prevent the overgrowth of aquatic plants in a pond.

Mechanical removal is the most expensive and physical way of removing plants from a pond. This can be done by cutting the unwanted plants with a cutter and then raking in the loose plant matter. The most important advantage of the mechanical method is that the vegetation is immediately removed from the water column, which helps with water quality. Removing the vegetation from the pond means no decaying organic matter to cause drops in dissolved oxygen, leading to a fish kill. A significant disadvantage includes the disposal of plant matter from the bank. If large quantities are collected from the pond, this usually means hauling off large masses in motorized vehicles. Other disadvantages include the ineffective removal of portions of the vegetation and the dispersal of vegetative fragments that may take root elsewhere.

Using EPA-approved chemical herbicides is probably the most effective means of controlling the excessive growth of aquatic plants in a pond. The initial step to controlling plants with herbicides is correctly identifying the aquatic plant and deciding how much of the plant matter is to be removed from the pond. After careful identification, an aquatic herbicide can be selected for use. Please read and follow label recommendations precisely as with all pesticides because labels can change; by law, the label is the final legal document on herbicide application.

According to the label, proper handling and use of herbicides pose no threat to the environment or human health. Aquatic herbicides are easy to use and offer safe, quick responses to controlling the specific aquatic plant. Using herbicides instead of mechanical control can be cheaper, and less labor is needed to remove the aquatic plant from the pond.

The best remedy for biological control is the triploid grass carp. Grass carp are considered herbaceous and can feed on various plant matter, and being triploid, they cannot reproduce. Identifying the aquatic plant is still necessary to see if grass carp is a long-term solution to the excess growth of aquatic plants in the pond. Grass carp are a popular choice in adding biological control because they can consume their body weight in vegetation in a single day, are more aggressive in consuming the foliage when they are young, and grow to more than 50 pounds. Grass carp feed mainly on soft-stemmed submersed aquatic plants and are recommended primarily to control these aquatic plants. The pond owner chooses to stock grass carp; some things should be considered initially. Grass carp should be stocked at 10 to 12 inches to reduce predation if more prominent bass reside in the pond. Emergency spillways should be screened and protected so that the grass carp are not allowed to escape.

The most cost-effective methodology for aquatic plant control combines two or more management strategies into an integrated effort. Herbicides and mechanical removal should be considered a temporary fix. Control duration can range from a few weeks to several months, depending on the herbicide selection and the plant species. However long, control can be achieved by combining recommended control methods such as using the proper herbicide applications followed by triploid grass carp stocking.


Lance Beecher, Cooperative Extension Specialist

This information is supplied with the understanding that no discrimination is intended and no endorsement of brand names or registered trademarks by the Clemson University Cooperative Extension Service is implied, nor is any discrimination intended by the exclusion of products or manufacturers not named. All recommendations are for South Carolina conditions and may not apply to other areas. 

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