Fighting Back Against the Chestnut Invasion

Contributing Reporters on this Newscast:


Somerville, MA, July 29, 2014 – Despite the work of giant skimming machines and the hundreds of volunteers, water chestnuts continue to clog the Mystic River.

First introduced to the area in 1897 by a gardener as an ornamental garden in Fresh Pond, Cambridge, the water chestnut (Trapa natans) is an invasive species native to Asia, Europe and Africa. Because it has no major competitor or predator, the plant has spread through the region. Today, water chestnuts can be found on lakes, ponds and waterways from Virginia up through Ontario, Canada.

Here in eastern Massachusetts, the Mystic River Watershed Association is fighting back.

“It’s definitely a long-term project for us, but we’ve been working on it now for five years,” Beth MacBlane, Outreach Coordinator of the Mystic River Watershed Association (MRWA), told Somerville Neighborhood News.

The plant was not always as big problem as it is today. Water chestnuts were only “here and there” at the start, MacBlane said. Then, “it just exploded and became very obvious very, very quickly that we needed to be involved in the removal and eradication.”

On July 12, scores of volunteers gathered at the Blessing of the Bay boathouse to lend a hand to the eradication program. In fact, so many people signed up, the MRWA had to close registration.

Working mostly from canoes, the volunteers filled 889 baskets with the pesky plant. So far this summer, MRWA events have amassed some 3,800 basketfuls.

Hand-pulling is the only option for the areas close to shore, but it barely makes a dent in the chestnuts. Beginning in 2011, the MRWA had to start hiring “harvesting” machines that collect the plants by churning them up onto a deck. The chestnuts are made into compost.

“They’ve got a million seeds and they go down to the bottom and lay dormant,” harvester operator Ron Huntley of Aquatic Control Technology, Inc., told Somerville Neighborhood News. “Just like politics. Goes on forever!”

Harvesting needs to take place during the summer, before the flower turns to fruit, as the plant is highly prolific. Left unchecked, one acre of plants can produce as many as 100 acres of plants a year later, according to some studies.

“If you wait too late in the year, the water chestnut has already produced its fruit,” Tufts professor Colin M. Orians explained.

“Those fruits will flow long distances and they’ll sink down into the mud,” he added. “The fruits can stay dormant for up to 12 years,” and then germinate.

The water chestnut drives out other species by taking up oxygen and room for other plants, and by clogging waterways.

There is one more chestnut-pulling event, on August 9. For details, visit this link.

For more information, U.S. Department of Agriculture website here.