National Invasive Species Awareness Week – Water Chestnut

Posted on: March 2nd, 2018 by Samantha Kahl

Welcome to the final day of National Invasive Species Week! Thank you all for sticking with us. We hope you’ve learned a great deal and will continue efforts in preserving our native species! Last, but not least, we look at the aquatic invasive Water Chestnut.

Water Chestnut is native to Eurasia and Africa, introduced to the U.S. in the mid-1800’s as an ornamental plant. It is found in freshwater lakes and slow-moving streams and rivers. First notice in Scotia, NY, Water Chestnut occurs in 43 counties across New York State.

Indentification

Water Chestnut is an annual plant with floating triangluarly-shaped leaves containing saw-toothed edges. The submerged, hollow air-filled stems grow 12 to 15 feet in length that anchor themselves in the soil. Four-petaled, white flowers bloom in June, with fruits containing 4-inch spines with barbs. Seeds within the fruits remain viable up to 12 years. The fruits are key in spreading Water Chestnut, as they detach from the stem and float to another area. The barbs aid in attaching the fruit to recreational watercrafts and fishing equipment.

Leaf system of Water Chestnut. photo courtesy of Northeast Aquatic Nuisance Species Panel

Leaf system of Water Chestnut.
photo courtesy of Northeast Aquatic Nuisance Species Panel

Water Chestnut. photo courtesy of Northeast Aquatic Nuisance Species Panel

Water Chestnut.
photo courtesy of Northeast Aquatic Nuisance Species Panel

Fruit of the Water Chestnut. photo courtesy of NYS Parks Boat Stewards

Fruit of the Water Chestnut.
photo courtesy of NYS Parks Boat Stewards

So what’s the problem?

Water Chestnuts contain dense root mats that make water recreation extremely difficult to get through. These dense mats also shade out native plants, which provide food and shelter to native  fish, birds, and insects. When the dense mats decompose, the chemical processes involved decrease the amount of dissolved oxygen in the water, potentially suffocating fish and plant species. The fruits of the Water Chestnut are often found along the shoreline and bottom of waterways, making the barbs of the fruits extremely painful if stepped on.

What can be done?

A variety of methods in controlling Water Chestnut include manual, mechanical, and chemical methods. Early detection is the best way to control and even eradicate this invasive aquatic plant, keeping costs and ecological impacts low. Hand-pulling is often done to smaller infected areas, though, when a site is too large, harvesting machines can also be used. Chemical treatments should be done by NYS DEC professionals only.

As a local community member, make sure to Clean, Drain, and Dry your watercraft and equipment before and after each use. Be sure to dump your bait bucket water where it came from or on land.

If you think you have found Water Chestnut, take a look at the Water Chestnut Fact Sheet. If confirmed, the NYS DEC asks you take many photos and submit a report to iMapInvasives. Please share this information with others!


For more information regarding local infestations of Water Chestnut, check out the Esopus Creek Conservancy here. Thank you again for taking time to explore invasive species with us during National Invasive Species Awareness Week! Check back soon for more updates from the Ashokan Watershed Stream Management Program!

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