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Water Chestnut Early Detection on iNaturalist

May 15, 2021 - May 22, 2021

Localities, pond management personnel and the general public are asked to look for a new species of Water Chestnut (genus Trapa) (http://mdinvasives.org/iotm/june-2018/) recently found in the
Potomac Watershed. Its name is Trapa bispinosa Roxb. var. iinumai Nakano. It has been spreading since 1995 so you may have already encountered this floating aquatic vegetation growing over the surface of a pond, lake or other fresh waterbody. This species of Water Chestnut is identified by the seed cases having two spines instead of four found on Trapa natans. Although we encourage to report any Trapa species you may see out there. Don’t forget to snap a picture of the seed cases!

Water Chestnut (an annual plant) will sprout in May, spread over the water surface and then flower and fruit by July; it drops seeds all season until it senesces after a hard frost. To stop the spread, management by harvesting the plants by early July is very successful in eradicating the plants but it may take several years of effort, if some seeds fall before harvesting the plants or lay dormant in the current year and sprout in a later

This is a project of the National Capital Region Partnership for Regional Invasive Species Management (NCR-PRISM). The NCR-PRISM aims to restore natural habitats and ecosystems and to protect biodiversity by managing invasive species and doing prevention efforts through a coordinated effort across political and ecological boundaries. The NCR-PRISM currently has 14 federal, local, and nonprofit member agencies and organizations.


May 15, 2021
May 22, 2021
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