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TVA River Neighbors

Weather could help or hinder aquatic plant growth this summer

The hot, dry weather in recent years has damaged pastures and crops and wilted lawns and gardens across the Southeast, but it has provided good conditions for the growth of aquatic plants.


One of the most abundant submersed aquatic plants in TVA-managed reservoirs is Eurasian water milfoil. First introduced into the Tennessee River system in the 1950s, this opportunistic species roots in bottom sediments and grows at water depths of a few inches up to 10 feet. In shallower portions of reservoirs, it often grows to the water’s surface and forms dense mats that affect recreation use. Photo by Alison Fox, University of Florida.

TVA aquatic biologist David Webb explains: “When you have droughts, you’ll generally see a spike in aquatic plant populations. The clear water that results from low flows and lack of runoff allows sunlight to penetrate further into the water, and aquatic plants — milfoil, hydrilla, spiny-leaf naiad, pondweed, and coontail, for example — respond accordingly with increased growth and expansion into deeper water.

“Most tributary reservoirs have few or no aquatic plants because water levels fluctuate so much from summer to winter. But on some main Tennessee River reservoirs — Pickwick and Kentucky, for example — we’ve seen an increase in aquatic plant populations since the drought began.”

Whether this trend will continue depends on Mother Nature, says Webb. “The recent wet weather could delay the onset of aquatic plant growth this summer. But if drought conditions return, we can expect another good crop.”

Aquatic plants begin growth from the reservoir bottom and may become visible in many areas by mid-June.

Boaters and those using jet skis should avoid areas with aquatic plant growth as the fragments can clog propellers and motors. Recreational activities such as swimming and bank fishing may also be impacted in areas of dense growth. Later in the year, unusually high flows or winds may trigger a breakup that results in numerous fragments and floating surface mats that can clog intakes at water and industrial plants, as well as power generating facilities.

Although considered an unsightly nuisance by many, aquatic plant growth does have its benefits. Anglers appreciate the fact that young fish use the structure as cover and tend to thrive in areas with significant plant populations. Aquatic plants also benefit waterfowl and other wildlife by providing food and habitat for small organisms that live on the stems and leaves of the plants.

What you can do

If excess aquatic plants are a problem around your dock or shoreline, hand-harvesting offers a potential solution for small areas. It may be hard work, but it’s low-cost, it doesn’t leave a chemical residue in the water, and it’s easy to target specific problem areas.

The simplest harvesting method involves removing a plant’s root system by pulling from its base. Submerged plants also can be removed by raking or by using V-shaped cutters that have a rope attached to the handle. You can throw the cutter out from the shore or dock, and it cuts the plants at their base as it is pulled back in.

It is important to remove pulled or cut plants from the water so that fragments won’t take root and form new plants.

Chemical treatment is another means of controlling particular aquatic plants, but extreme care must be taken to protect the environment and multiple treatments may be required. Your state resource agency can provide information about necessary permits and help you find a licensed commercial aquatic herbicide applicator.

How TVA can help

TVA can provide technical assistance related to state permit requirements along with information to help shoreline property owners identify and manage aquatic plants in an environmentally sound manner. For more information, call TVA’s Environmental Information Center at 800-882-5263 or use this online form.


Stop aquatic hitchhikers

Most of the problem-causing aquatic plants in TVA-managed reservoirs are exotic species that were introduced from other countries. Natural controls such as insects and diseases usually prevent these plants from becoming problems in their native ranges. But without natural controls, these plants can spread rapidly and crowd out native species.

Boaters can help stop the spread of exotic species by thoroughly cleaning their equipment. Every time you pull your boat out of the water, drain your motor, bilge, and live wells and rinse your boat and trailer with hot water. Empty bait buckets into the trash or dispose of bucket water on dry land far from shore.

If you have a water garden or an aquarium, be sure to dispose of unwanted plants properly. Allow them to dry out after you remove them; then place the dried plants in your compost pile or bag them for disposal in a landfill.



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