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Invasive Species



In 2000, variable milfoil (Myriophyllum heterophyllum​) was discovered in the Squam Lakes and River. The Squam Lakes Association has tirelessly worked to keep this submerged invasive aquatic plant controlled. Our efforts hand-pulling and using a Diver Assisted Suction Harvester for removal have proven successful; there has not been a new infestation of variable milfoil identified on the Squam Lakes since 2007. While our efforts mainly focus on variable milfoil, we also keep an eye out for any other invasive plants that may try to sneak their way into Squam.


Throughout the summer, the SLA has Lake Hosts both the public boat launch on Route 113 in Holderness and our own Piper Cove launch. Lake Hosts greet boaters as they enter and leave the lake, educate boaters of the dangers and locations of aquatic invasive species, and offer to perform a voluntary boat inspection to ensure that no plant material is traveling on boats as they enter and exit the lake.

Community Involvement

Early detection of aquatic invasive species is the first line of defense. The SLA has worked with communities around the lake to establish neighborhood Weed Watchers, groups of dedicated volunteers that survey their shorelines in search of invasive aquatic plants and animals.



There are several terrestrial invasive plants in the Squam Watershed. The Squam Lakes Association partners with other area conservation groups to identify the locations of invasive plants and to create an action plan to manage these infestations.


Throughout the summer, the SLA hosts terrestrial invasive plant removal mornings. Participants learn best methods for removing specific terrestrial invasive plants and get their hands dirty removing these invasive species.

Current Projects

The SLA is working on the eradication of invasive species at the Cotton Mountain Trailhead, including Japanese Knotweed (Reynoutria Japonica) and Round Leaf Bittersweet (Celastrus Orbiculatus). These species form dense thickets that crowd out native species and have other negative consequences for the local environment. Rather than the use of chemical herbicides, the SLA is removing these species by mechanical means and smothering them with weed barriers. These techniques can take up to five years to completely eradicate the invasives, so the Cotton Mountain Trailhead will look different until it can be revegetated with native species.

Inquire About Invasive Species