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Preventing the Spread of Invasive Aquatic Plants: A Photo Essay in Four Phases

Susan Onion, Co-Founder, and Ash Holland, Staff Writer
16 April 2026
Susan Onion, Co-Founder, and Ash Holland, Staff Writer
16 April 2026
ADVOCACY AND MOVEMENT BUILDING
A travel team volunteer surveys Upper Mattawamkeag Lake.
Photo credit: Susan Onion
When invasive aquatic plants appear in Maine lakes, experts and volunteers know it’s time to act. These plants threaten everything from wildlife habitats to the state’s economy, crowding out native plants and affecting the waters that are valued by all who enjoy and rely on them.
Protecting Maine’s freshwater resources takes a coordinated and collaborative effort among organizations such as Lake Stewards of Maine, Lakes Environmental Association, 7 Lakes Alliance, 30 Mile River Watershed Association, the Maine Department of Environmental Protection, local municipalities, lake associations, and hundreds of dedicated volunteers.
Together, these experts and volunteers educate, survey, map, remove, and monitor invasive plants — working to keep the state’s lakes clean and healthy for all.
Phase One: PreventionCourtesy Boat InspectionsPhoto credit: 30 Mile River Watershed AssociationInvasive plants most often travel by boat, so trained volunteers educate boat owners to inspect their equipment at boat launches to prevent the spread of invasives from one water body to another. Here, a Courtesy Boat Inspector examines a vessel for invasive stowaways at Androscoggin Lake.
Phase Two: Early DetectionCommunity EducationPhoto credit: Susan OnionLake protection organizations host workshops to train community volunteers to identify characteristics of invasive aquatic plants. In this photo, volunteers inspect reference sheets at a workshop hosted by Lake Stewards of Maine.
Lake SurveysPhoto credit: Susan OnionVolunteers and members of watershed protection organizations regularly survey lakes from boats or by swimming to monitor the presence of invasive plants like variable-leaf milfoil or swollen bladderwort. This image shows this work in action, as a volunteer snorkels in Wilson Pond, patrolling for invasive aquatic plants.
Phase Three: Control and Remediation EffortsMappingPhoto credit: 7 Lakes AllianceIf an invasive plant is introduced into a lake, organizations work together to survey the littoral zone, or the depth at which sunlight no longer penetrates to the bottom. Teams then map the infestation via organized sections of the lake. Here, North Pond Association volunteers mark areas with invasive curly-leaf pondweed.
Growth PreventionPhoto credit: Alex Walls, 7 Lakes AllianceTeams pull burlap mats known as benthic barriers to block the sunlight aquatic plants need to grow, preventing the spread of already established variable-leaf milfoil. This image shows volunteers pulling a 30-by-50–foot mat on Great Meadow Stream, Great Pond.
Plant RemovalPhoto credit: 7 Lakes AllianceTeams use various techniques — including hand-pulling plants from their roots, using diver-assisted suction harvesting technology, or applying herbicide — to remove an invasive plant from a lake. In this photo, a diver carries a bag of invasive variable leaf milfoil pulled from Messalonskee Lake.
Plant DisposalPhoto credit: 7 Lakes AllianceAfter they’re removed from the lake, invasive plants are then bagged and sent to be composted. Here, two divers from 7 Lakes Alliance float next to their harvest at Oakland Public Landing on Messalonskee Lake.
Phase Four: Ongoing MonitoringMonitoringPhoto credit: 30 Mile River Watershed AssociationSince most invasive plants spread easily and rapidly, organizations regularly monitor affected areas to identify any new infestations and control their spread. Here, an invasive plant patroller looks through a scope and documents any signs of invasive aquatic plants.
Read More About Maine’s Lakes