Biogen at the Arlington Reservoir, removing water chestnut.

Biogen at the Arlington Reservoir, removing water chestnut.

The Mystic River Watershed Association runs two volunteer-powered invasive plant management programs, one tackling the aquatic plant water chestnut and a second program removing Oriental bittersweet from waterfront parks. More than 700 volunteers participate in these programs each year, significantly improving the health and aesthetics of the river. Volunteer opporunities run from June - October.


Join the list of companies who make a difference in the Mystic! MyRWA can organize a fun and rewarding employee community service day for you. Learn more about our corporate opportunities here. If you would like to get your workplace, community organization, church, club or neighborhood involved in invasive plant management please contact us at 781-316-3438 or

Photo Oct 18, 10 00 09 AM.jpg

Oriental Bittersweet

As part of the Mystic Greenways Initiative and due to the popularity and success of the water chestnut removal project, the Mystic River Watershed Association launched the Oriental bittersweet removal project in 2016. Focusing on Medford's Macdonald Park this land-based stewardship activity tackles the invasive vine that can kill tress, impairs habitat value and degrades park aesthetics. 

Oriental bittersweet (Celastrus orbiculatus) is a woody vine that grows rapidly and can easily climb trees up to 90 feet tall. As Oriental bittersweet grows, it chokes or girdles the plant that it is clinging to, shades out other plants and makes trees top-heavy, making them susceptible to wind and ice damage. It is easily identifiable in the fall by its red and orange berries.

Water Chestnut

Photo Jul 14, 11 16 28 AM.jpg

Eradication efforts of water chestnut, an invasive plant clogging the Mystic River and elsewhere in the watershed, have been ongoing since 2010. MyRWA is aggressively combating water chestnuts by partnering with municipalities, local environmental organizations, boat clubs, corporations and community members to hand-pull the plant and obtain funding for a mechanical harvester. Because of all the works we are doing the volume of water chestnut in the river has drastically decreased! Check out a time-lapse video of volunteers in action.

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. In Medford, parts of the Mystic River were 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 that 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.


  • 2018: 793 volunteers removed 2,403 baskets of water chestnuts and 1,850 lawn bags of Oriental bittersweet.

  • 2017: 996 volunteers removed 5,200 baskets of water chestnuts and cleared 18 acres of parklands of invasive plants.

  • 2016: 835 volunteers attended 22 events, removing nearly 67 tons of plant material from the Mystic River and Arlington Reservoir.

  • 2015: 966 volunteers hand-pulled 94,160 lbs. of water chestnuts across 21 events. Program news coverage!

  • 2014: 941 volunteers attended 19 events removing 6,603 baskets of water chestnuts, clearing 2.3 miles of the Mystic River.