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September 24, 2018

Volunteers Help Curb Spread of Water Chestnuts


FULTON, NY – This past Saturday, a group of 12 volunteers hand-pulled the invasive water chestnuts from the Battle Island area of the Oswego River.

At the Battle Island  Cove entrance, Sandy Davis in foreground pulls up several rosettes growing from one stem and nutlet. In the background are Naneen Drosse, Mary Gillen and Brian Levendusky. (Photo by Dick Drosse)

At the Battle Island Cove entrance, Sandy Davis in foreground pulls up several rosettes growing from one stem and nutlet. In the background are Naneen Drosse, Mary Gillen and Brian Levendusky. (Photo by Dick Drosse)

The Battle Island area along with the old Oswego lock nearby, are of significant historical importance and a popular fishing and canoeing/kayaking location.

The water chestnut (Trapa natans) has small triangular toothed leaves growing together in a circular form known as a “rosette.” Its small, white, four-petaled flowers grow into black, four-pointed “nutlets” commonly encountered when they wash up along the shore.

If stepped on, they can cause painful injury.

Water chestnut can form dense mats, interfering with boating, fishing and swimming.

Local groups hold water chestnut “pulls” to reduce their spread.

It is critical that these pulls take place before the seeds are released. The seeds may remain viable for up to 12 years.
Each rosette (the floating top pad) can produce multiple nutlets, which in turn, each produce new water chestnuts, according to Dick Drosse, one of the event’s organizers.

Mary Gillen in the foreground, snaps off  the rosettes (which grow the nutlets) killing the plant. Photo by Brian Levendusky)

Mary Gillen in the foreground, snaps off the rosettes (which grow the nutlets) killing the plant. Photo by Brian Levendusky)

The dormancy of a nutlet can be up to 10 years, so rechecking and annual pulling is necessary.

Where water chestnuts have been pulled for the last seven years, results have been positive with no or little growth showing.

The establishment of water chestnut can result in large floating mats of vegetation that “clog” aquatic habitats and limit the penetration of sunlight into the water column, impeding the growth of native plants and ultimately disrupting the food web.

Hand-pulling where individual or clusters of the water chestnuts are found growing can greatly reduce and eliminate the water chestnuts from those locations.

Key areas where the hand-pulling was done were at the cove entrance of the west side of Battle Island, an area with clusters near the Battle Island Golf Course and in a section of the historic Oswego Canal.

A positive reduction in growth of the chestnuts in these locations has been identified over the last several years, from the hand-pulling efforts.

Pulling water chestnuts near Battle Island Golf Course is,  Margaret Bocsor in foreground. (Photo by Brian Levendusky)

Pulling water chestnuts near Battle Island Golf Course is, Margaret Bocsor in foreground. (Photo by Brian Levendusky)

Water chestnut, native to Europe, Asia and Africa was unintentionally released into the Charles River from a Harvard University botanical garden in the late 1800s.

It was known to exist in the Great Lakes Basin by the late 1950s.

The nutlets from the water chestnuts can stay dormant for more than six years, so continued inspection is necessary.

Each nutlet of the water chestnut plant can produce multiple plants, with each plant producing an average of 6 -10 nutlets.

On average, a water chestnut plant can produce as many as 300 seeds per year.

By snapping off the stem about 18″ below the floating rosette, the plant will die.

As advocated by Oswego County Soil and Water Conservation District, a grassroots effort by hand-pulling can remove the water chestnuts from thinly spread out areas, where the mats of chestnuts have not formed yet.

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