Huron Pines and the City of Harrisville Working Together to Eradicate Japanese Knotweed

Harrisville, MI—Huron Pines, is helping the City of Harrisville remove an invasive plant that can wreak havoc on building foundations and underground utilities like sewer and water lines. Japanese knotweed is a legally prohibited invasive species in Michigan, that grows aggressively and gets even bigger when mowed, plowed or cut. The only way to treat it is with herbicide application, which is precisely what the Huron Pines field crew has been contracted by the City of Harrisville to do this summer.

In 2014, representatives from the city of Harrisville, Huron Pines, Alcona Conservation District and Friends of Negwegon State Park met to discuss management plans for an outbreak of Japanese knotweed across the city. The plants were likely decades old and were found in patches ranging from 100 square feet to half an acre in size. Knotweed not only damages foundations, sidewalks, driveways and substructures, it can also take over yards and open spaces due to its rapid growth. It was a priority for the city to keep it from spreading and develop a plan for removal.

“The City of Harrisville continues to have an ongoing, working relationship with Huron Pines in their effort to eradicate the invasive species of Japanese Knotweed within the city,” explained Barbara Pierce, Clerk for the City of Harrisville, who has been involved with the project since the beginning. “The City of Harrisville realizes this continues to be a work in progress and is encouraged with the progress made thus far.”

Since 2015, Huron Pines has been treating the plant with repeated and targeted chemical application. The targeted application makes it possible to treat the knotweed without damaging desirable plants that are meant to be part of the landscape. It can take multiple applications over several years for the plant to be eradicated. Over the last three years, Huron Pines has been able to reduce the size and scope of the treated knotweed by 50 percent. Each year, a new inventory is conducted ahead of treatment to identify any new growth and to determine how effective previous treatments have been in order to make any adjustments.

“We want to make sure we are treating all of the knotweed across the city so that we can keep it from spreading any further,” said John Frye, Huron Pines Habitat Project Manager. “The ultimate goal of eliminating invasive species is to protect and restore the native plants to support wildlife and the overall health of the ecosystem.”

The Huron Pines field crew was out taking inventories around the city the week of June 18 and will be back to treat the plants in July and again in September with the hopes that two treatment rounds will accelerate the progress. If you have any questions about the treatment or have Japanese knotweed on your property that you would like to have treated, please email

basement knotweed (1)Japanese knotweed growing through a basement foundation next to an egress window.