By Amy Buskey

If you visited Ellis Pond recently or are a resident along the water’s edge, chances are you took notice of the warning sign posted there back in early June. The Norwood Conservation Commission informed residents that the pond would be chemically treated for control of nuisance vegetation – that nuisance being the non-native European water chestnut. But these plants go way, way beyond being just a nuisance. The truth is, these plants cause a host of problems on our waterways. First off, because the floating plants form dense mats on the water’s surface, it makes it harder for wildlife to find food. It also makes it hard for boats, canoes, kayaks, and the like to move across the water for simple recreation. Left unchecked, it will also result it low oxygen levels in the water and fish dying off. According to longtime resident Keith Anderson, who lives on the ponds’ edge, that has already happened.

“The fishing is way down from previous years,” Anderson said. “The problem gets worse each year. The growth used to peak at the end of July, now it’s peaking in June.” 

Anderson, who spends a great deal of time on the pond, did see the change following treatment. 

“It actually got rid of the thinly populated weeds in the deeper area of the pond but half of it is still covered,” Anderson said. 

And that is the limitation of herbicides when it comes to invasive species like the monster we now know as water chestnut. Herbicides only target newer growth, on the plants that have not yet produced seeds for the following year. During a single season, one acre of Water Chestnut can produce enough seeds to cover 100 acres the following year, resulting in a monster of a problem.

Native to Europe, Asia, and Africa, water chestnut plants are kept in check in these countries by their native insects. But controlling the invasive species here in the Unites States has proven difficult, incredibly costly, and often requires several different tactics to target just one body of water. So how did water chestnut get here? Gardeners brought it here from Europe sometime in the 1870’s and was known to be growing in a botanical garden at Harvard University in 1877. Around the same time, a gardener reported growing it in Fresh Pond in Cambridge, as well as other local ponds, and from there began an invasive nonnative plant epidemic of sorts. The plants easily spread and took hold as their seeds found their way through connecting ponds and rivers. The hardy annual species is also well established in both the Concord and Charles River systems, along with countless other rivers, ponds, and streams from here to Canada. 

Water chestnut has also been known to hitch a ride on the feathers of wildlife, so completely eradicating the plant altogether is unlikely, at least for now. There are also the people who unknowingly transport water chestnuts. Over at Walden Pond in Concord, for example, they employ a boat ramp monitor to ensure boats coming in do not have any stowaways, that being the dreaded water chestnut. And it is working. The pond is one of the very few in the area that have no invasive or nonnative plant problems. The herbicidal control measures at Ellis Pond have been repeated all over the Northeast, and they are in fact just that – control. There simply is no magic bullet, much to the dismay of locals, and controlling the plant will be perpetual. It has taken decades to research how to control it and has costs millions. Take for example, Lake Champlain. They spend upwards of half a million dollars annually to keep the plants under control. There’s also neighboring Canton at Silk Mill Pond. A few years back there were no water chestnut growing there, but by 2020, nearly 80 percent of the pond was covered in it. They too employed numerous methods to contain it, including hand pulling and herbicides. But hand pulling is no easy task and requires hours of volunteer work - plants can reach up to 15 feet from the base of ponds and rivers. They reproduce primarily by the production of nuts, and each nut can produce 10-15 plants. And then each of these plants can produce up to 20 seeds. The 6-gram nuts are released in the fall and sink into sediments where they can stay viable for up to 12 years. Therefore, regardless of the type of treatment, it should take place before the fruit or nut has ripened and settled into sediment. 

Rising up out of this sediment of doom to save our beloved ponds and waterways could be beetles, Asian beetles, specifically. We cannot talk water chestnut problems without bringing in the work of Bernd Blossey, associate professor of natural resources at Cornell. Blossey has been conducting research for decades on controlling water chestnut through means of Asian beetles, a natural biocontrol. Blossey received permission to bring Asian beetles back to the U.S. in 2019, and since then has been conducting studies at Cornell on their effectiveness. Although more time is needed, it looks like Asian beetles may be our best bet in the very near future in getting our ponds and waterways back to good health. And for folks like Anderson, that help can’t come soon enough. 

“The west end of the pond is not navigable,” Anderson explained. “The water’s natural flow is being inhibited by the weeds.” 

Anderson has spent more time than most out on the water in his small motorboat RIGA. For decades he, like many others, have enjoyed Ellis Pond in its earlier healthier days. Now, in retirement, Anderson looks out onto the water, remembering how it used to be. 

“It’s disappointing that the town isn’t taking care of its only body of water,” Anderson said. 

Norwood, like so many other towns throughout the Northeast and beyond, waits patiently for that next line of defense against Asian water chestnut. That next defense will likely come-a-calling in the shape of a beetle, only this time, nature can’t call soon enough.