Our aquatic plant management program targets the troublesome, invasive species hydrilla (Hydrilla verticillata), water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes). 

Invasive aquatic plants

These attractive foreign species were introduced to Florida with no regard for their potential to cause ecological and economic harm.

Water hyacinth


Water hyacinth is a free-floating plant native to South America. It was introduced in Florida during the late 1880s. It currently infests 218 public water bodies in Florida and many more private waters. Water hyacinth has a fast growth rate (populations can double in as little as two weeks) and expands rapidly on Florida waters. Unmanaged waters typically become filled with dense, floating mats of water hyacinth. This species caused such severe problems that federal efforts to control water hyacinth were initiated by Congressional action during the 1890s.



Hydrilla is a rooted, submerged plant native to Southeast Asia. It was introduced to Florida during the late 1950s as an aquarium plant and now infests 175 public water bodies. It is a rapidly growing plant (can grow an inch a day) that has the ability to fill lakes and rivers from the bottom to the surface with a tangled mass of stringy stems. Special physiological adaptations allow hydrilla to grow in much deeper water than other aquatic plant species. Because of this special ability, the growth of hydrilla is not limited to shallow shoreline areas of lakes. Hydrilla has the demonstrated potential to fill most Florida lakes from shore to shore if not controlled.

Water lettuce

water lettuce

Water lettuce is a free-floating plant. Its native range and date of introduction to Florida are not known. Experts disagree on whether to consider water lettuce a native or introduced species. It has been present in Florida for a long time and occurs on 152 public waterways. Water lettuce reproduces and spreads rapidly, often covering significant portions of lakes and rivers.

Plants brought to Florida from foreign lands are typically introduced here without the natural pests, diseases and other environmental conditions that limit their growth in their native lands. The ability of these species to rapidly reproduce, coupled with the lack of any natural controls, enables them to proliferate at the expense of beneficial native plant communities. Excessive populations of these plants negatively impact navigation, recreation and flood control, and decrease property values. Dense infestations can reduce dissolved oxygen levels, increasing the potential for fish kills to occur, damage fish and wildlife habitat and significantly hinder fish management and restoration efforts. The annual growth cycle of these species, coupled with their ability to rapidly produce large, dense populations, increases the formation of sediments (muck accumulation).

Because of the well documented negative impacts of these species on Florida's aquatic resources and commerce, Florida Statute 369.22 was passed requiring that these invasive plants be managed at the lowest feasible level. The Southwest Florida Water Management District conducts aquatic plant management operations in cooperation with the Florida Department of Environmental Protection and the Florida Fish and Wildlife Conservation Commission.

Populations of these plants are continuously monitored and controlled to maintain them at the lowest feasible level. Managing these troublesome plants at low levels minimizes the amount of plants which must be treated, resulting in reduced treatment costs, herbicide use, associated ecological impacts, damage to fish and wildlife habitat and recreational impacts.

Water use restrictions

The use of treated waters for irrigation or other purposes may be restricted following the application of aquatic herbicides, which are used to control invasive species populations. Each product has a unique mode of action, chemical properties and research data package. For this reason, the required water use restrictions are different for each product and some aquatic herbicides have no water use restrictions at all.

Water use restrictions apply only to “treated waters.” Treated waters consist of the actual area on which the aquatic herbicide was applied, as well as an appropriate buffer or setback distance. Water use restrictions may occasionally apply to an entire lake or section of a river if a lakewide infestation of the troublesome species hydrilla is treated.

See the herbicide table below for applicable water use restrictions for aquatic herbicides utilized by the Southwest Florida Water Management District. Treatment areas will be posted with warning signs displaying treatment dates and applicable water use restrictions.

Please check out these interesting links for more plant pictures and information relating to invasive and native aquatic plants, statewide aquatic plant management efforts, weed alerts and information on available control methods.

Herbicide Table — Water Use Restrictions Summary

Applies to withdrawal of treated surface waters, not tap or well water. This table displays the various herbicides the District uses and their related water use restrictions. There is no restriction on the use of treated waters for swimming, fishing or boating.

Aquatic Herbicide Applicable Water Use Restrictions
Aquathol K Potable Water1
Irrigation: 7 days2
Animal Consumption: 14 days (non-flowing water only)
Aquathol Super K Potable Water1
Irrigation: 7 days2
Animal Consumption: 14 days (non-flowing water only)
Clearcast Potable Water1
Clipper Irrigation: 5 days
Galleon Irrigation4
Komeen or Nautique No water uses restricted
Tribune, Reward or Knockout Irrigation (turf/ornamentals): 1–3 days
Irrigation (food crops): 5 days
Livestock consumption: 1 day
Potable Water: 0–3 days1
Rodeo or Aquastar Potable Water: 0–2 days1
Sonar or Avast Potable Water: 0–2 days1

1Restrictions on the use of potable water are rarely required because setback distances established by the U.S. Environmental Protection Agency are observed. If a potable water use restriction was required, it would be coordinated with the local utility that provides potable water who would switch to a different water source so consumers would not be affected.

2Wait 7 days before irrigating nursery, greenhouse, newly seeded or transplanted plants, crops or turf.

3Irrigation restrictions dependent on application rate, distance, and plants being irrigated. Some applications require no irrigation restrictions.

4Irrigation restrictions dependent on application rate, site treated and plants being irrigated.

Weeding Out Invasive Aquatic Plants PDFView or download our brochure, Weeding Out Invasive Aquatic Plants PDF

Weekly treatment schedule ยป

The District's treatment schedule can be found on the Florida FWC website. Just enter the name or partial name ("Pan" for Lake Panasoffkee or "with" for Withlacoochee River) of the lake or river you are interested in.

Scheduled operations may be cancelled due to unfavorable weather or environmental conditions, or manpower and equipment availability.

For additional information, please call Brian Nelson at 1-800-423-1476 (FL only) or (352) 796-7211, or email Brian Nelson email.

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