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Invasive Species Alert - Two-horned Water Chestnut

April 01, 2024 12:00 AM | Anonymous member (Administrator)

Mark Debord and Lara Weatherholtz – Apr 2024

Many of those who live at Lake Anna are familiar with Hydrilla, an invasive plant native to Asia. Hydrilla started in the US in Florida in the 1950’s. It was originally imported as an aquarium plant but was released into Florida waterways. It has now spread throughout much of the Southeast and many other areas of the US.

Another invasive plant, also from Asia, is the Two-horned Water Chestnut. It was first identified in Virginia in 1995. Thus far, it has been limited in Virginia to ponds in Northern Virginia, though a more recent infestation was found in farm ponds in Charlotte County.

Two-horned Water Chestnut is a floating aquatic plant. As with Hydrilla, it can form dense mats that interfere with boating and other aquatic sports. It grows in water depths of 1-15 feet. It can choke out native species and decrease water oxygen levels. And, like Hydrilla, it can be very difficult to eradicate once established.

Thus far, we have not identified any Two-horned Water Chestnut plants at Lake Anna. However, the seeds are spread by geese and other waterfowl, so it’s not unreasonable to believe it could find its way here. Surveys conducted last year in parts of the lake did not locate any infestations.

Below are some resources to help identify the plant. We ask that you keep an eye out for this while on the lake. It sprouts in April and May and soon spreads over the water’s surface. It flowers and fruits in July, before dying back in cold weather. If you see any, please contact LACA’s Environmental Preservation Committee Co-Chairs Mark DeBord ( or Lara Weatherholtz (

Please don’t try to eradicate the plant yourself, especially with herbicides. This could inhibit our ability to track and more effectively eliminate it. And remember, removing any aquatic vegetation requires following Dominion’s policy.  Lake Anna Reservoir and WHTF Vegetation Management & Herbicide/Pesticide Treatment Policy (

If you have any questions, please contact Mark or Lara.

Invasive Species Alerts – Blue Ridge PRISM Inc

water chestnut (Trapa bispinosa var. iinumai) - Species Profile (

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