ST. LAWRENCE EASTERN LAKE ONTARIO PARTNERSHIP FOR REGIONAL INVASIVE SPECIES MANAGEMENT
Myriophyllum aquaticum, commonly referred to as parrotfeather, is an aquatic plant native to South America. Spread by human dispersal, mainly by the aquatic plant trade for aquarium and garden ponds, this plant has spread invasively across at least 26 states in North America, and around the world.
Despite being invasive in many regions, Myriophyllum aquaticum is still commonly sold as a water garden plant, which has the potential to escape into local waterways. Parrotfeather can be found in freshwater lakes, ponds, and canals with slow-moving waters, growing prolifically in shallow areas and waterbody edges. This invasive plant contends with native aquatic plant communities, forming dense mats that can entirely cover the surface of the water providing habitat for mosquitos.
Once established in a new environment, Parrotfeather easily spreads downstream in the form of vegetative fragments or attached to ships or boats. There are only female plants in North America, meaning there are no seeds produced from the plants in the U.S. The foliage dies off in winter, and the roots produce new shoots in the spring.
Parrotfeather is a Tier-1 species, meaning it is not known to be present within our region, but it is within a 100- mile radius, and a clear pathway exists. An established population of parrotfeather was found in Onondaga County in 2025. Once established, control of this plant is extremely costly, making early detection a critical measure to protect our region’s native plant diversity and access to our waterways.
Parrotfeather is in the milfoil family (Myriophyllum), but New York is home to a variety of native milfoil species that serve important roles in our ecosystems. Parrotfeather stands out with its unique chartreuse coloring and stiff plastic-like appearance.
Farwell’s watermilfoil (Myriophyllum Farwellii)
Myriophyllum aquaticum (Parrotfeather) is best controlled using systemic herbicides (e.g., 2,4-D, Triclopyr, Imazamox) combined with surfactants to penetrate its waxy cuticle. Mechanical harvesting is ineffective and spreads fragments, though hand-pulling small, isolated patches can work. Integrated management, including winter drawdowns and reducing nutrient runoff, is recommended. For best results, a combination of the methods outlined below, tailored to the specific site, should be used.
Prevention is the first and preferred approach when managing any invasive species. Being aware of and able to identify aquatic invasive species like parrotfeather is crucial for successful prevention. Clean boats, trailers, and equipment thoroughly after leaving infested water bodies
Hand-pulling and mechanical removal may be used to control populations, although care should be taken to remove all plant pieces from the water.
Cutting or mechanical harvesting is enerally not recommended because it spreads fragments that will take root.
Bottom barriers can be used to shade out and suppress growth in small areas.
Chemical Treatment: The use of herbicides in water is regulated; always consult state and local regulations for required permits.
Biological Control:
Take a clear, close-up photo, note the location (GPS coordinates are best), and report observations to NYiMapInvasives or directly to the SLELO PRISM’s Aquatic Restoration and Resiliency Coordinator, Adrien Owens, Adrien.Owens@tnc.org.
Education and stewardship are the most effective ways to prevent invasive species from establishing. Join our Water Protector’s Program to support early detection of this and other aquatic invasive species. Participants learn to identify and report priority species to NYiMapInvasives and adopt a waterbody for annual monitoring
SLELO PRISM also offers the Aquatic Invasive Species Learning Experience (AISLE), a three‑part training held annually that includes a virtual ID session, a hands‑on workshop, and a guided paddle.