PlantFiles: Hydrilla, Water Thyme
Hydrilla verticillata

Hydrilla, Water Thyme Hydrilla verticillata is naturalized in Texas and other States is considered an invasive noxious plant and is prohibited in Texas.

Hydrilla or Waterthyme (Hydrilla verticillata) is one of the worst aquatic exotic weeds in much of Florida and parts of the southern United States (zones 7a through 11). It can survive as far north as zone 5a (15 to 20 degrees below 0).

In Florida, Hydrilla has infested thousands of acres of water bodies. In one report, it was estimated to cover around 40 percent of public water bodies in Florida by around 1991 (credits to info in the Hydrilla chapter of the book "Identification and Biology of Non-native Plants in Florida's Natural Areas" by K.A. Langeland and K. Craddock Burks, Editors). It's removal has cost thousands and millions of dollars from water bodies, canals, lakes, streams, ponds, public water bodies and boating/watercraft bodies/channels throughout Florida.

Hydrilla is extremely agressive in growth habit. Once established, it can quickly spread and form vast, underwater spreading thickets and monocultures that push out native aquatic plants and smothering them - and also by preventing sunlight from reaching the surface bottom. It also grows at, near, or to the surface of the water.

Hydrilla is a weedy, snakelike waterweed. In many areas, waterways for boaters have become virtually impassible due to the infestation of Hydrilla. The weed quickly becomes entangled in boat moters, preventing watercraft from moving very affectively. This has also closed many public water bodies for swimming due to the huge infestations of this weed.

The release of Hydrilla into bodies of water (either by ballast, aquarium releases, discardment, ect.) has probably resulted in it's successful establishment in several states in the U.S., especially in the South.

Hydrilla has been found naturalized in the U.S. in about 16 states. It is a prohibited species by the U.S. and a Category One Invasive by the Florida Exotic Pest Plant Council (FLEPPC).

Hydrilla is found naturalized in at least 24 counties in Florida, from Miami-Dade and Collier counties northward throughout much of the state.

Hydrilla has also been found naturalized (and equally agressive) in many warm tropical, subtropical, and warm temperate regions worldwide.

This should serve as an avid warning against planting this aquatic danger anywhere - AT ALL. It is fairly hardy, too - so be warned.

HINT: Hydrilla is known as "The Perfect Waterweed" due to it's agressiveness.

IT SHOULD NOT BE RELEASED INTO ANY BODY OF WATER ANYWHERE.

U. S. FEDERALLY LISTED NOXIOUS WEED.
Not allowed for import to the US and not allowed in any interstate or intrastate transportation without a specific permit from USDA APHIS PPQ (Plant Protection and Quarantine).
No one should be selling/growing this plant in the U.S.

FYI: This plant is a Class A Noxious Weed in the state of Vermont. Its movement, importation, sale, possession, cultivation and/or distrbution is prohibited with fines upto $1000.00 possible.

Once sold as an aquarium plant, Hydrilla is commonly referred to as "the perfect waterweed" because of its invasiveness, ability to form thick mats that choke waterways and pose a hazard for boat motors.