Hydrilla (Hydrilla Verticila) is a submerged aquatic plant that roots in the bed of a waterbody. It is native to Africa, Australia, and parts of Asia. It is considered the most problematic aquatic plant in the US. there are two varieties of hydrilla in the US; one produces only female flowers making it dioecious, while the other is monoecious and produces both male and female flowers. The plants in New York are monoecious and produce both female and male flowers. It is believed that hydrilla was introduced in the US via the aquarium trade. Hydrilla is a federally listed noxious weed, listed as a Class A weed on Washington’s Noxious Weed List, and is on the Washington State Department of Agriculture’s Quarantine list
Hydrilla invades deep, dark waters where most native plants can’t grow; it is more efficient at taking up nutrients than native species and has the ability to produce turions and tubers which can easily generate new plants–these characteristic give hydrilla a competitive edge against native aquatic vegetation. Furthermore, hydrilla populations block out sunlight and suppress native vegetation. Major hydrilla colonies can alter the physical and chemical characteristics of lakes and deter recreational activities and reduce lakeshore property values.
Hydrilla is found in freshwater bodies and is well established throughout southern portions of the US.
Prevention: Hydrilla can easily sprout new plants from root and stem fragments and is easily spread by boat propellers and other aquatic recreational equipment. Therefore, to prevent its’ spread it is important for boaters to Clean, Drain, Dry their boats and equipment before leaving/entering a body of water.
Physical control: Hydrilla can be controlled physically by hand removal via snorkelers and divers. It is important to remove tubers from plants to be successful with this control method.
Chemical control: Aquatic herbicides can be used but type and regulations depend on the state. Contact the local DEC office for information.
Top photo collage in clockwise order: Chris Evans, River to River CWMA Bugwood.org; Michael Frank Galileo Group Inc. Bugwood.org; Robert Videki, Doronicum Kft. Bugwood.org. Hydrilla vs look-alikes photos in clockwise order: Tim Krynak Cleveland Metroparks, Bugwood.org; Leslie J. Mehrhoff, University of Connecticut, Bugwood.org;Graves Lovell, Alabama Department of Conservation and Natural Resources, Bugwood.org. Native look-alikes of Hydrilla and Brazilain Waterweed compliments of Lake George Association.