Stop Invasive Water Chestnut this Spring

An invasive species of plant has recently arrived in our Potomac River Watershed. If we act soon we can still stop it. This new species of water chestnut is a relative of the well-known invasive species Eurasian water chestnut. Once water chestnut shows up in a water body, it spreads to cover large areas and, if allowed to flower and reproduce, can spread far and wide carried by Canadian geese and other wild life. This plant forms dense floating mats that cover the water surface, blocking sunlight and killing aquatic grasses and vegetation. Dr. Nancy Rybicki formerly of the U.S. Geological Survey and now teaching at George Mason University came to the Potomac River Watershed Roundtable to ask for our help in stopping the spread of this water chestnut.

Right now this new species of water chestnut is confined to Fairfax and Prince William counties, but its sites are doubling each year. It is spreading in stormwater ponds, farm ponds, golf water hazards, and ponds in parks. Once it flowers with a pink flower it produces a 2 horned fruit with barbs that attach to wildlife, but are sharp enough to puncture a shoe. The water chestnut is an aquatic annual herb. The fruit though horned and barbed is edible and has medicinal qualities. It sprouts from seeds in spring and the plants die off in winter after a hard frost, but the seeds can lie dormant for several years and be washed from a spill way down river. 

from USGS

It can still be stopped. If it is pulled out before it flowers in July, it can be easily killed with a little follow up in early summer and in the following couple of years. It can be eradicated in 2-5 years at a site. The photo below is from Pohick Bay in Lorton, Virginia in 2014 when the USGS and Virginia Game and Inland Fisheries Program studied and worked with Volunteers to remove the water chestnut from Pohick Bay. The picture is from John Odenkirk of VGIF. 

If you spot the plant please report it to John.Odenkirk@dgif.virginia.gov or 540-899-4169. If you would like more information or help in in spreading the word, please contact Dr. Rybicki at nrybicki@usgs.gov or call her at 703-624-1318