Harvesting Water Chestnuts

On Thursday, August 28, 2016, I had one of the more interesting and satisfying paddling experiences I have ever had. No, my day did not include an enjoyable and scenic float down one of our beautiful rivers. Instead, I spent a very hot morning harvesting (pulling, actually) and hauling away a very pernicious aquatic non-native invasive plant – water chestnuts.

We had been contacted by Cathy St. Andre, Park Ranger for the U.S. Army Corps of Engineers at West Thompson Lake, looking for volunteers to help pull non-native invasive water chestnuts from the lake. The Last Green Valley has partnered with Cathy and her team on several projects over the last few years so we were glad to help out. While I had heard about the water chestnut problem, I have to admit that I knew very little about the plant. That was about to change with an up-close and personal encounter!

I was joined by my TLGV colleague LyAnn Graff, TLGV’s Water Quality Monitoring Coordinator Jean Pillo, and several other TLGV volunteers. We arranged to meet Cathy and one of her colleagues at the West Thompson Lake boat ramp. I had the 17-foot TLGV canoe, Cathy had an Army Corps canoe, and everyone else was in kayaks. After a brief introduction to the removal process we paddled to the north end of the lake to a large 30 square foot patch of water chestnuts.

So what are water chestnuts? Here are some quick facts from a US Fish and Wildlife Service fact sheet:

• Water chestnut (Trapa natans family Trapaceae) is a rooted, aquatic plant with both floating and submersed leaves that grow in shallow areas of freshwater lakes and ponds, and slow-moving streams and rivers. The floating leaves form a rosette and are green, glossy and triangular with toothed edges. The submersed leaves are feathery, and are found whorled around the stem. Plant stems are cord-like and can attain lengths of up to 16 feet.

• Water chestnut is an annual plant, overwintering entirely by seed. In July the plant begins to produce seeds (called nuts) with 4 sharp spines. Mature seeds are green to greenish brown and sink to the bottom. Seeds may remain alive in the sediment for up to 12 years! (Please note: this plant species is not the same as the “water chestnut” used in Asian cooking.)

• Water chestnut’s native range is Europe, Asia and Africa. Since its introduction into North America in 1877 it has become a nuisance species because of its ability to reproduce rapidly and form dense floating mats severely limiting light – a critical element in aquatic ecosystems. Once established, it can reduce oxygen levels, increasing the potential for fish kills. It competes with native vegetation and is of little value to waterfowl. Water chestnut infestations limit boating, fishing, swimming and other recreational activities. Further, its sharp fruits, if stepped on, can cause painful wounds.

• Early detection is the key to control since smaller populations are easier to eliminate than larger ones. It also costs less to control a small infestation because plants can be individually hand-pulled. Large populations require the use of mechanical harvesters or application of aquatic herbicides to achieve control. Infested waters must be treated for 5-12 years to eliminate the invading population. However, some infestations are so extensive that complete eradication may never be achieved.

According to Cathy St. Andre, water chestnuts were first sighted in West Thompson Lake in 2011. Since 2012, she and her team have been working diligently to remove the non-native invasive water chestnut from West Thompson Lake. “Due to the nature of this plant’s life cycle, it is possible to control the spread of plants by physically pulling the plants every year to stop them from dropping seeds to grow in subsequent years. If left untreated, this plant can effectively choke out a water body, which would make boating and fishing at West Thompson Lake all but impossible and would negatively impact the aquatic habitat of the lake for both plant and wildlife species.”

As our small flotilla of boats approached the first large patch of water chestnuts, we were not quite sure what we had gotten ourselves into. We reached into the water, grabbed the root stems and slowly and gently pulled the plants, uprooting them from the muddy bottom and hauling them into our boats. The kayaks were soon covered with the wet green plants and my canoe was soon filled to overflowing.

This was a wet, muddy and dirty job, but we also quickly saw results and in just over an hour the large patch was completely removed from the lake. It took us three trips with the filled canoes and kayaks to a landing on a road near the lake. We hauled the plants from our boats and made a large pile that eventually reached over six feet high and twenty feet square. The plants were then picked up by a front-end loader and put into a dump truck for removal to an area far from the lake where they will rot and decompose.

After “harvesting” the first large area of water chestnuts, we paddled to another large patch and repeated the process of slowly pulling the plants from the muddy bottom and into our boats. This time we returned to the boat launch and loaded the plants into a waiting dump truck to be hauled away with the first patch.

Each of us was muddy, wet, hot and a bit tired. Despite this, we were also very satisfied that in just a few hours we had made a significant dent in the water chestnut infestation at West Thompson Lake.

Cathy and her team rely on help from volunteers to control this aggressive invasive plant and she is always looking for more assistance. If you are interested in helping remove water chestnuts from West Thompson Lake, please contact Park Ranger Cathy St. Andre at 978-318-8562 or Catherine.st.andre@usace.army.mil. She will be going out two more days this summer and also will be organizing a large-scale removal effort in late June 2017.

Volunteers are the life blood of many organizations that make a difference in our Last Green Valley communities. In many cases, volunteer opportunities with organizations working to preserve and protect our natural resources require getting outdoors and doing physical work. Take it from me, this can be very rewarding and worth the effort.

Last week the volunteers that joined Cathy St. Andre to pull water chestnuts at West Thompson smiled through the mud and wet, laughed at the huge piles of plants in our boats, and looked back with tired muscles on a job well done.

I hope you’ll join me and others in caring for, enjoying, and passing on the wonders of our beautiful region.

Bill Reid is the Chief Ranger of The Last Green Valley National Heritage Corridor and has lived in the region for more than 30 years. He can be reached at bill@tlgv.org

The Norwich Bulletin is granted first serial rights and associated electronic rights to publish the preceding article.  The Last Green Valley, Inc. retains all other rights to the work.