OARS Water Chestnut Project

Name: Alison Field-Juma  Organization: OARS  Phone: 978-369-3956

Site location:
Assabet River, Hudson through Concord, MA; Concord River from confluence with Assabet to Lowell.

Basic property description:

Assabet and Concord Rivers, in Westborough and Hudson to Lowell, mainly the impounded sections

Management area description:


Acres in the management area: 550  Listed on EDDMaps? No

Habitat type: River

Was this Early Detection Rapid Response (EDRR)? No

Initial Overall Invasive Distribution Description:

Scattered to heavy, mainly in the shallow, slow-moving sections of the impoundment area of the river. Maps available at CISMA webpage.

Initial Overall Percent Cover of Invasives: 76 - 100%

Target species:

Invasive Species
Initial Percent Cover
Water Chestnut (Trapa natans)  

Management objectives:

Reduce the populations of water chestnut to levels that can be managed, with relatively low effort, by hand-pulling. Prevent new areas of infestation and prevent the spread from existing areas.

Approximate project start date: June 1, 2019

Years this project has been ongoing: 4

Project summary:

OARS’ Rapid Response Team is hired from June-August to hand-pull water chestnut along the Assabet and Concord Rivers everywhere that it was found. Volunteers also engaged in hand-pulling on several impoundment sections of the river plus the Sudbury River at Rte 2.


Control method: Manual

Disposal method: Composting off site (away from river edge)

Detailed project timeline:

June-Aug: Survey the sections to be managed before pulling
June-Aug: Repeat hand-pulling every summer with hired help and/or volunteers

Funding sources: 2016 funding came from two Supplemental Environmental Project penalty funds

Final acres in management: 550

Open to the public: Yes

Able to Provide Tours: Yes

Success Rate: Moderately successful

Current Overall Percent Cover of Invasives:

Comments / Takeaways

The population of water chestnut varies in response to summer conditions (rain and temperature), although the plant is an annual the seeds have a long (12+ years) viability in the sediment, and new seeds are transported by wildlife and flooding to new areas. Maintaining consistent control efforts indefinitely is thus essential.

Last Updated: July 21, 2020