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.

Current U.S. range map of Hydrilla verticillata


Hydrilla stems are long (up to 25 feet in length) that branch at the surface where growth becomes horizontal and forms dense mats.


Leaves are small (2 – 4 mm wide, 6 – 20 mm long), pointed, often serrated and arranged around the stem in whorls of 4 to 10.

Tubers are pea-like structures buried in the sediment; they are 0.2 to 0.4 inches long and off-white to yellowish in color.


Hydrilla can be distinguished from its native look-alikes elodea (Egeria densa) and American waterweed (Elodea canadensis) by observing a few characteristics: First, hydrilla will have tubers, whereas, elodea and waterweed don’t have tubers.

Other Characteristics to look for are in the abundance of leaves and leaf appearance.


Compliments of Rob Williams

Hydrilla has serrated leaflets that grow in whorls of 4 or more around the stem

Elodea has no leaf serrations and grows in whorls of 3 around the stem

Elodea has no leaf serrations and grows in whorls of 3 around the stem


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.

Photo Credits:

Introduction photo: Habitat/Distribution map, Identification photos of stem, leaves, and tubers, Washington State Noxious Weed Control Board and


Aquatic Invasive Species: Hydrilla. N.p., 2010. Web. 22 Oct. 2015. <>.

“General Information About Hydrilla .” Non-native Invasive Freshwater Plants. N.p., n.d. Web. 22 Oct. 2015. <>.

“Hydrilla.” Noxious Weed Control Board (NWCB). N.p., 2010. Web. 22 Oct. 2015. <>.


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Prevent the introduction of invasive species into the SLELO PRISM.

Rapidly detect new and recent invaders and eliminate all individuals within a specific area.

Share resources, including funding personnel, equipment, information, and expertise.

Collect, utilize, and share information regarding surveys, infestations, control methods, monitoring, and research.

Control invasive species infestations by using best management practices, methods and techniques to include: ERADICATION (which is to eliminate all individuals and the seed bank from an area), CONTAINMENT (which is reducing the spread of established infestations from entering an uninfested area) and SUPPRESSION which is to reduce the density but not necessarily the total infested area.

Develop and implement effective restoration methods for areas that have been degraded by invasive species and where suppression or control has taken place.

Increase public awareness and understanding of invasive species.

Develop and implement innovative technologies that help us to better understand, visualize, alleviate or manage invasive species and their impacts or that serve to strengthen ecosystem function and/or processes.

Rob Williams
PRISM Coordinator

Megan Pistolese
Outreach and Education

Brittney Rogers
Aquatic Invasive Species

Robert Smith
Terrestrial Invasive Species