Invasive Water Chestnut Finds Its Way Into Connecticut River

The seed pod of the invasive water chestnut is an evil-looking thing.

Hard, round and spiky, it could, as one observer pointed out, be confused with a very small medieval mace.

Dozens of the seed pods were on display Tuesday in Old Saybrook during the “Meet Your Greens” meeting, sponsored by the Rockfall Foundation, an environmental education and conservation group based in Middlesex County. The environmental talk before about a dozen people featured Judy Preston, of the Tidewater Institute and Margo Burns, an environmental planner with the Connecticut River Estuary Regional Planning Agency.

The two women spoke about the spread of the water chestnut, an Asian water plant that has started to invade tidal and inland waters in New England, including the Connecticut River.

Both environmentalists urged those who attended the meeting, many of them members of the Rockfall Foundation, to report the locations of sightings of the water chestnut so environmentalists can track the water weed and plot its spread on a GPS mapping system.

The water chestnut is a rooted water plant that has both floating and submerged leaves. The plant, experts say, is not the same as the water chestnut used in Asian cooking. 

Seed pods can hitch rides on fibrous materials on boats and the water plant began showing up in U.S. waterways around 1877.  It has become a dangerous nuisance in some watercourses – one patch covers 500 acres in Lake Champlain, Preston said – because it reproduces quickly and forms dense, floating mats that can choke out native species and block sunlight to the water, depleting oxygen in the water. That, in turn, can start to impact fish and other aquatic life, she said.

The plant reseeds over the winter and seed pods can live for up to 12 years in the muddy bottoms of rivers and lakes.

“This,” Preston said while holding up one of the seed pods, “will actually change water temperature, oxygen levels and the penetration of sunlight.”

Preston said the plant has begun to flourish in some still water areas of the lower Connecticut River, including Hamburg Cove in Old Lyme and the Chapman Pond area in East Haddam. Left unchecked, the weed could begin to show up in other areas of the river, she said.

“In terms of wetlands, this is a top concern because it grows so fast and it can fill in a wetlands area quickly,” Preston said.

“If we can keep an eye out for it and keep a handle on it, that would be great,” added Burns.