The Problem

How did Hydrilla and Hygrophila get here?

The plants were brought here in the 1940s and 50s as aquarium plants. It is likely they were released in Florida waters by aquarium enthusiasts. Because they have no natural enemies to keep them in check, they have been able to spread rapidly throughout our waterways. Both hydrilla and hygrophila continue to be sold through aquarium supply dealers and over the internet, even though the plants are on the U.S. Federal Noxious Weed List.

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Millions of dollars are spent each year to control invasive aquatic plants (particularly hydrilla) in Osceola County. If not kept in check, these plants can create serious navigation blockages, cause major flooding, and interfere with boating, swimming, and fishing. Native desirable plants can be displaced and the overall health of the ecosystem can suffer.

An eight-foot deep central Florida lake
An eight-foot deep
central Florida lake
filled with hydrilla.

Hydrilla (Hydrilla verticillata) and hygrophila (Hygrophila polysperma) are among the worst of the invasive aquatic plants and they can spread easily via fragments broken off from plants in the water. Both plants can grow in any type of fresh water; the only exception is that hygrophila grows primarily in flowing water. They can also grow in low light levels, so the plants can thrive in very little sunlight. Since hydrilla and hygrophila grow quickly in a variety of conditions, they out-compete our native plants, displacing them from their environment.

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Helicopter spraying herbicide treatment
Helicopter spraying
herbicide treatment.

Aquatic plant management techniques that have been implemented in the past and are currently practiced include: herbicide applications, mechanical harvesting, biological control (including the use of grass carp) and large scale habitat restoration, all of which are extensive uses of labor and funds. Aquatic plant management in Osceola County ponds and lakes is ongoing. The main technique used by managers is herbicide application using helicopters and airboats. Large-scale herbicide treatments of hydrilla in Lake Toho and nearby lakes are periodically conducted to keep hydrilla infestations under control. To learn more about aquatic herbicides, see "Why Aquatic Herbicides Affect Aquatic Plants and Not You!" PowerPoint and the EPA (Environmental Protection Agency) web site.

One of the big problems in the Kissimmee Chain of Lakes (including Lake Toho) is that hydrilla has become resistant to fluridone, a herbicide that used to provide cost-effective and long-term hydrilla control. The Osceola County Demonstration Project seeks to find better control techniques for hydrilla and other invasive weeds.

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Osceola County Demonstration Project

The primary purpose of the Demonstration Project is to discover new herbicides, develop new technology processes or practices, or new combinations for the purpose of proving technologically feasible and cost effective means to manage hydrilla, hygrophila and other exotic aquatic vegetation in the Kissimmee Chain of Lakes in Osceola County. Learn more information about the Demonstration Project here.

Find out more about the economic impacts of aquatic weeds in Osceola County (PDF - 358 KB).

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How You Can Help

Boat propeller with Hydrilla.

Preventing the introduction and spread of non-native invasive plants in Florida is the most effective and least expensive way to protect Florida’s natural habitats. Here are a few things we can all do:

  • Learn to identify which plants are invasive, especially in your area.
  • Always remove plant matter from boats and trailers after use.
  • Practice good stewardship: never transport Florida’s aquatic or wetland plants to other areas, and never empty your aquarium into a body of water (not even a ditch).
  • Volunteer to help remove invasive plants in your area.
  • Avoid chopping aquatic plants with boat propellers as some plant fragments can grow into new infestations.
  • Get the word out! By telling others about invasive plants, we can help prevent their spread.

Learn more about what you can do to prevent the spread of non-native and invasive plants:

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