What's Happening Now

National Invasive Species Week: Part 2

Japanese Knotweed and the Judicious Application of Herbicides

By Matt Eddy, MMOC Staff

Knotweed is a widespread invasive found throughout the Muddy River Restoration Project area. You may notice there’s a lot less of it along the Riverway than there used to be. The Emerald Necklace Conservancy, collaborating with Boston’s PowerCorps, has undertaken a significant removal effort that has opening up new views of the River.  

Removal isn’t a simple task because knotweed has the capacity to regrow and even expand from root stock if the plant is cut above ground. To address this, herbicide injection is sometimes used. A certified professional may inject herbicide (typically RODEO®, an herbicide similar to RoundUp® but permitted for use near bodies of water) into the cut stems of the knotweed. The effort is timed to match the season of greatest vulnerability for the plant (early fall). This is an environmentally safer method of herbicide treatment than spraying the leaves. Repeated cutting in conjunction with herbicide treatment has shown success as a management strategy and is recommended by the UMass Agricultural Extension.

Large patch of knotweed along the Riverway at Netherlands Road, October 25, 2022:

Same location one day later:

Knotweed stems are cut back so they can be injected with herbicide:

Mitigating the harmful impacts of invasive species along the Muddy River is a primary goal of the Muddy River Restoration Project. And the work is ongoing. Long after the last excavator leaves the Project area, we, as River stewards, must prioritize long-term monitoring and maintenance so the gains made to date continue.

Photos: Matt Eddy