First introduced to the Lake in the 1940s, water chestnut (Trapa natans L.), is a nonnative plant that forms dense surface mats, crowding out other plant species, disrupting habitat, and severely limiting recreational enjoyment and commercial use of the Lake in some areas. Water chestnut grows each year from distinctive spiny seeds which are the key to controlling the spread of the plant.

If the plants are removed from the Lake before the seeds are dropped, water chestnuts can be eliminated. Water chestnuts are removed from Lake Champlain by both a mechanical harvester and by hand-pulling. The Water Chestnut Range graphic shows the extent of infestation on Lake Champlain from 1960 to 2003.

Since the early 1980s, the Vermont Department of Environmental Conservation, with support from the US Army Corps of Engineers, has run a harvesting program to control the spread of water chestnut in Lake Champlain and prevent its introduction to other areas. Funding is also provided through the Lake Champlain Basin Program. As shown on the Lake Champlain Water Chestnut Annual Funding chart, annual funding is critical to slow the northward spread of water chestnuts. Beginning in 2000, the New York State DEC and Canal Corporation also provided funding for mechanical harvesting in Lake Champlain's South Bay, which is near Whitehall, NY (not included on chart).

New infestations in 2003 were found on Porters Lake (Ferrisburg, VT), North Springfield Resevoir (VT), a private pond in Bennington, VT, and at Stoney Point on Lake Champlain (Benson, VT).

The Nature Conservancy (TNC) organizes volunteers to hand-pull water chestnuts that have established themselves in new areas of the lake, and where large mechanical harvesting equipment cannot be used. From 1998 to 2003, TNC pulled 207 tons of water chestnut by hand with the help of volunteers. Volunteers are needed each summer--call TNC at (802) 265-8645 to get involved. Volunteers to help survey in the Adirondacks are also needed by the Adirondack Park Invasive Plant Program.

A "northern" water chestnut colony was discovered in Quebec's Richelieu and South Rivers in 1998. These rivers are close to Missisquoi Bay, whose shallow waters would be prime habitat for water chestnuts. Perhaps more alarming is that some plants were found near the mouth of the Pike River in 2001, which drains directly into Missisquoi Bay. Fortunately, no water chestnuts have been found there since.

The Quebec Ministry of Environment is working closely with local groups in Quebec, as well as the VT DEC and the LCBP to control this spread and find funding for harvesting and hand-pulling. In 2002, Quebec began mechanical harvesting on the South River, and has worked with many volunteers to hand-pull the plants. To get involved with Quebec programs, call CIME Haut-Richelieu at (450) 346-0406.

Recreational boaters can help control the spread of water chestnut to more lakes and ponds by following some easy tips. Please read "Help Stop the Spread of Nuisance Species."

• Adirondack Park Invasive Plant Program
• Water Chestnuts (VT DEC)
• The Nature Conservancy