Hydrilla

Hydrilla is highly adaptable. It thrives in still and flowing waters, including rivers, lakes, ponds, wetlands, streams, and wet ditches, and can also tolerate a range of nutrient and light conditions. The plant grows up to 2.5 cm a day. It has a competitive advantage over many native plants because it begins photosynthesis (converting sunlight to energy that helps it grow) earlier in the day than most plants. Because tiny plant pieces can develop into new plants, hydrilla can easily spread when water currents, boat propellers, trailers, fishing gear, or people carry plants or plant fragments to new areas (Ontario, 2018).

Size: Stems grow up to 9 m in length; leaves are 6-20 mm long and 2-4 mm wide.

Hydrilla was detected for the first time in Canada in 2024 at Hillman Marsh Conservation Area located in Leamington, Ontario. In the United States, it has spread across the southern states from Florida to California, along the west coast in California and Washington, along the entire Atlantic seaboard, and inland through Pennsylvania, Indiana, Wisconsin, New York, and several other states. Populations can now be found on every continent except Antarctica (Ontario, 2018). 

Hydrilla is an adaptive and fast-growing invasive aquatic plant that can alter habitat and negatively impact native species (Ontario, 2018):

• Once established, hydrilla is able to grow aggressively and outcompete native plants.
• It forms dense mats that block sunlight from reaching other submerged plants, including native species.
• Hydrilla degrades water quality by raising pH levels, decreasing oxygen, and increasing water temperature.
• It can hinder the flow of water and impact recreational activities such as swimming, fishing, and boating.
• Hydrilla can provide habitat that allows mosquitoes to breed by causing stagnant water.

Learn how to identify hydrilla and avoid accidentally spreading this plant with your watercraft. (Ontario, 2018)

Report sightings of hydrilla through the EDDMapS or iNaturalist websites or mobile device applications or by calling the Invading Species Hotline 1 (800) 563-7711. A good report includes an accurate location of the sighting and photos. 

For aquarium enthusiasts and aquascapers:

• Avoid planting hydrilla in your aquarium or water garden. Aquarium hobbyists and water gardeners are advised to use only native or non-invasive plants and are encouraged to ask retailers for plants that are not invasive.
• Never release unwanted aquarium plants or pets. Return or donate unwanted plants to a garden centre or pet store, or put them in the garbage.

For watercraft users:

• Avoid infested areas or reduce your speed when travelling near infestations. Your propeller can break off fragments and spread the pieces to new areas. New plants can grow from small fragments of the plant.
• Inspect your boat, trailer, and equipment after each use. Remove all plants, animals, and mud before moving to a new waterbody.

For hunters:

• Switch to elliptical, bulb-shaped, or strap anchors on decoys, which avoid collecting submersed and floating aquatic plants. 
• Clean. Drain. Dry. any watercraft used while hunting.  
• Inspect equipment, waders/ hip-boots, and other gear and remove aquatic plants and rinse mud from them before leaving. 

For anglers:

• Inspect all your fishing equipment (lures, fishing rod, nets) for any aquatic plants, and rinse any mud before leaving.  
• Clean. Drain. Dry all watercraft used while fishing.  
• Do not dump the contents of your bait container into or within 30 m of any body of water.