You Can Beat Knotweed Without Chemicals—Here’s How

Japanese Knotweed, present in Vermont since before the 1920s, is a highly competitive perennial species native to Japan. Originally introduced in the U.S. to stabilize eroding hillsides, it’s since become a widespread and problematic invasive species. With bamboo-like stalks that can grow over 10 feet tall in dense thickets, Japanese Knotweed is a familiar—and unwelcome—sight near many riverbanks in the Lake Champlain Basin.

Because it spreads aggressively and outcompetes native vegetation, knotweed harms native plant communities, pollinators, and waterways. It’s most commonly found on streambanks, floodplains, and roadsides. It spreads during flood events—when rhizome fragments wash downstream—or via contaminated fill or roadside debris.

If knotweed shows up on your property, your choices are limited: watch it spread, use chemical herbicides, or engage in years of persistent physical removal. Chemical treatment is not tolerable to some landowners and watershed groups because it poses risk to other plants and wildlife and is not all that effective on deeply rooted rhizomes.

In 2021, a Vermont resident approached the Lewis Creek Association (LCA) to explore herbicide-free methods to tackle knotweed. In response, LCA launched a knotweed removal program with guidance from invasive species expert Mike Bald and funding from the Lake Champlain Basin Program/NEIWPCC.

That summer, the team, including LCA technicians and community volunteers, began treating a knotweed thicket along Lewis Creek in Ferrisburgh. In 2025, they have returned to manage that site and have begun new treatment at a location in Starksboro. In 2026, they hope to add a third site, also in Starksboro along Lewis Creek.

Each site presents different challenges based on sunlight, soil, surrounding vegetation, and infestation size. “Each site is really different,” said Kate Kelly of LCA. “Management depends on how much knotweed is present, how long it’s been there, the physical characteristics of the site, and what other plants are around. Some sites are simply too infested for us to tackle this kind of physical removal.”

For areas that are too far gone for full removal, herbicide may be option, or frequent mowing around the patch edges may help prevent further spread. In general, the earlier the intervention, the easier the job. Even just 5–10 minutes a week of cutting or pulling can make a difference, especially if you catch it while the patch is still small.

Mike Bald and the team at LCA outline the best management practices in this guidance and outline document. In it, they split up the management process into three distinct phases.

Phase 1: Gain Control
The first step is understanding the size and edges of the patch. To reveal the full underground extent of the rhizomes, the team applies stress by cutting or snapping flush to the ground every stalk once a week during the growing season. The idea is to deny photosynthesis, forcing the plant to use up stored energy. Cut stems are dried on site using wooden pallets (called "Weed Drying Stations") to ensure that any rhizomes are fully exposed to sun and air, and not touching the soil. Tarps may be used underneath to prevent rerooting if there are many rhizomes present.

Phase 2: Kill the Roots
Over time, persistent cutting causes the plant to overextend. As it pushes outward seeking better conditions, the rhizome network begins to weaken. This phase can last several years as the patch contracts and native species begin to reclaim the space.

Phase 3: Eradicate and Restore
Finally, the team focuses on preventing regrowth and supporting native plant rebound. This is where introducing species that provide shade such as white pines, cedars, and hemlocks could help support the site and stress the remaining knotweed.

“This is a long-term program,” said Kate Kelly from LCA. “Over the first few years, we don’t expect to see much progress—and may actually see the patch grow laterally as it responds to the stress. However, it should get easier to manage each year, eventually getting to the point of full removal.”

Looking ahead, successful management relies on early detection, frequent management, and community stewardship. “Presence is our most powerful tool,” Bald writes. “When we’re on-site, we can observe how the plant responds and adjust accordingly.”

If you have knotweed on your land or want to help eradicate it from public areas, LCA has created a management guide for landowners and encourages folks to explore resources and reach out. To learn more at in-person removal sessions, sign up on their website. We're learning that the physical removal of knotweed is possible, and we want to help Vermont residents do just that.