Green Inferno: Invasive Plants Seize Stearns Reservoir

FRAMINGHAM, MA — Take a drive down Salem End Road toward Ashland, you might think Framingham has built a new park where the Stearns Reservoir used to be.

But, there is still a pond underneath the sea of green plants that sprouted recently. The plants are invasive water chestnuts, and their proliferation is actually part of a larger eradication plan.

Water chestnuts first appeared in Massachusetts waters in the mid-1800s, brought here from Europe or Asia, according to the federal National Park Service. The invasive plant has infested ponds and lakes across the state ever since, choking out native plants with its ability to grow very quickly.

The state Department of Conservation and Recreation, which oversees the Stearns Reservoir, is in the midst of a years-long effort to cull water chestnuts from the reservoir — as well as invasive milfoil and fanwort plants.

The plants don't pose much danger to humans, unless you step on a sharp seed pod, which can penetrate footwear. But water chestnuts do suck up a lot of oxygen in the water, which is harmful to fish. The floating leaves also collect organic waste, boosting pollution levels.

According to DCR spokesman Troy Wall, one strategy to eradicate water chestnut is to let all of its seeds bloom, making it harder for the plant to last more than a few seasons. In the meantime, you might see more water chestnuts than usual.

"This is due to the management of the water chestnut exposing the dormant seeds in the sediment to sunlight, which promotes propagation," Wall said this week. "This is an important process in the eradication of the species within the reservoir so that the seed base can be removed."

But don't expect the plants to disappear soon. Blooming the seeds out of existence can take up to 10 years (water chestnut seeds can stay dormant for up to 12 years). A similar effort at Fiske Pond in the Lake Cochituate system took three years, Wall said. DCR is also applying herbicide, and hand-pulling the weeds.

DCR's estimate for when the water chestnuts' seeds will be spent: three to five years.