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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