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upcoming events

Dec 12
Friends of the Malden River meeting, 6:30-8PM Cambridge Health Alliance, 195 Canal Street, Malden

Jan 3
Committee Meeting, 7-9PM
Tufts University, Tisch College of Citizenship & Public Service, Lincoln Filene Hall, Rabb Room, 10 Upper Campus Road, Medford




Water chestnut (Trapa natans) is native to Asia, Europe and Africa. It was introduced in 1897 by a gardener as an ornamental plant in Fresh Pond in Cambridge. Water chestnut has no primary consumers in the US, allowing for its unchecked spread. Read more about invasive species.


In Medford, parts of the Mystic River are barely passable due to water chestnuts that are working hard to extend their habitat from shore to shore. These floating-leaved plants form dense, continuous mats over the water surface of lakes, ponds and slow-moving waters. The mats in turn impede boating, fishing, and swimming, and crowd out native plants. Decomposition of large quantities of water chestnuts may result in lower dissolved oxygen levels, which can lead to fish kills. The plant’s growth is propelled by high levels of nutrients, such as phosphorus, in the Mystic River. One acre of water chestnut can produce enough seeds to cover 100 acres the following year. Each seed can give rise to 10-15 rosettes and each rosette can produce as many as 20 seeds. And if that wasn’t enough, seeds can remain viable for up to 12 years!



Hand harvesting Water Chestnuts in the Mystic RiverManaging water chestnut is a major goal of neighboring towns, boat clubs, river advocates, and citizen groups. MyRWA is leading a multi-year Water Chestnut Removal Project - read more here!

Volunteers have worked with local and state officials to organize removal of the plants by hand. Many areas including Little Pond, Little River, Yates Pond, Alewife Brook and Spy Pond are now free of water chestnuts since these vigilant water stewards have hand-pulled the plants year after year, assuring and tracking their demise. (For example, Roger Frymire, a long time volunteer in the Mystic River watershed, has completed the Ten Year Project Review of water chestnut eradication in the Alewife Brook sub-watershed.) 

However, the spread of the chestnuts now appears beyond the abilities of the hand-pullers in the Arlington Reservoir and the Mystic River in Medford and Somerville. Partnering with Massachusetts Department of Conservation and Recreation, Massachusetts Water Resources Authority, community groups such as Groundwork Somerville and Friends of the Mystic River, boat and yacht clubs, local businesses, and many volunteers, MyRWA is participating in a multi-year effort to address the problem and are researching potential sources of much-needed funding for mechanical harvesting on the river. Mechanical harvesting of water chestnuts occurred in 2011 - 2015.



Mechanical Harvester removes Water Chestnuts in the Mystic River 2010

Every volunteer hand-pulling water chestnuts makes a big difference! Join our team of volunteers at a Community Water Chestnut Event!



Do you have a group of people that would be interested in some fun team-building? A four-hour event with 25-80 people in canoes can have a tremendous effect, clearing acres of this invasive plant. By sponsoring a corporate event, your company can participate in a major green initiative while providing a great team-building opportunity and rewarding day on the river for your employees. We have worked with many organizations and companies over the past four years, and supply all the materials and expertise

Get your business or group involved to remove water chestnuts today! Contact for more information and to schedule events.


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