A Paddler’s Guide to Connecticut’s Invasive Aquatic Plants

By Janet Cunningham | July 28, 2026

Connecticut’s waterways are beautiful, but they face a growing threat from non-native, invasive aquatic plants. For paddlers who enjoy shallow, quiet coves, it is essential to understand these invaders and how to stop their spread.

Notable Invasive Plants

• Hydrilla (Hydrilla verticillata): An aggressive submerged plant that grows up to an inch a day, forming dense, multi-foot-thick mats. It is highly resistant to control and spreads easily through fragmentation.

• Water Chestnut (Trapa natans): A rooted, floating plant that produces dense, impenetrable surface rosettes. It also drops sharp, woody seeds that are hazardous to swimmers.

• Curly Leaf Pondweed (Potamogeton crispus): Known for its "lasagna-like" wavy leaves, this plant thrives in cool water and leaves behind decaying mats that trigger algal blooms when it dies back in summer.

• Variable Water Milfoil (Myriophyllum heterophyllum): A feathery, fast-growing plant that is extremely fragile. A single tiny fragment can easily break off and establish a new colony.

The Ecological Damage

Ecological Impacts of Invasive Aquatic Plants. Graphic by Janet Cunningham, Wanderlust Ecotours

These invasive plants do more than just block boat traffic; they fundamentally alter our ecosystems:

• Choking Out Native Life: Dense mats block sunlight, killing the native underwater plants that fish and invertebrates rely on for food and shelter.

• Creating "Dead Zones": Large mats consume excessive oxygen at night and during decay. This can lead to "anoxic" (oxygen-free) conditions, causing fish to suffocate.

• Disrupting Water Chemistry: By altering pH levels and oxygen cycles, these plants make it impossible for native species to thrive, turning healthy, diverse habitats into stagnant "dead zones."

Best Practices for Paddlers

Your gear is a primary vector for these plants. Preventing their spread is a personal responsibility for every paddler.

Extreme care is needed when paddling near Hydrilla as it is very fragile and easily fragmented.  Photo by Janet Cunningham

Prevention: "Clean, Drain, Dry"

• Inspect: After every outing, check your kayak, canoe, SUP, paddle, and life jacket. Remove all visible mud and plant fragments.

• Drain: Ensure all water is emptied from cockpits, hatches, and storage areas.

• Dry: Allow your gear to fully dry for at least five days  or wipe it down before entering a new body of water.

If You Encounter an Infestation

• Avoid: Steer clear of visible weed patches. The agitation of your hull or paddle is the number one cause of new infestations.

• If You Get Stuck: Do not power through or "muscle" your way out. Instead, use slow, shallow, gentle strokes to back out exactly the way you entered.

Other Ways to Help

Volunteer Chestnut Pull Event with the Pomperaug River Watershed Coalition

Photo by Janet Cunningham

• Reduce Fertilizer: Minimize or eliminate fertilizer use on your lawn. Runoff from rain carries excess nutrients into our waterways, which acts like "fuel" for invasive plant growth.

• Join a Pull Event: Water chestnut is a robust plant that can be manually removed. Many local groups, including the Connecticut River Conservancy, Friends of the Farm River & Estuary, the Quinnipiac River Watershed Association, the Pomperaug River Watershed Coalition, Jonas Center for Earth and Arts, and other organizations host community "pull events." These are great ways to meet neighbors, enjoy the water, and make a tangible difference.

• Stay Informed: Follow the work of the Connecticut Invasive Plant Working Group and report new, suspicious patches to the CT DEEP Invasive Species Program.

By staying vigilant and keeping your gear clean, you ensure that Connecticut’s waters remain healthy and accessible for everyone to enjoy.

About the Author: With thirteen years of experience teaching Earth Science and serving as a naturalist for the Audubon Society, Janet Cunningham brings a scientist’s eye and a teacher’s heart. As the owner and lead kayaking guide of Wanderlust Ecotours, she translates her passion for the natural world into immersive experiences that protect our environment. When she isn't in the classroom or leading tours, you can find her on the water, exploring and advocating for Connecticut’s vital ecosystems.