Japanese knotweed - Ask Extension
How do I get rid of Japanese knot wood? I’ve been ripping it out by the roots for years and it never goes away.
Knowledgebase
Japanese knotweed #872826
Asked June 12, 2024, 3:15 PM EDT
How do I get rid of Japanese knot wood? I’ve been ripping it out by the roots for years and it never goes away.
Ingham County Michigan
Expert Response
Hello Jennifer
As you have found, cutting alone does not control knotweed. Here are a couple bulletins that describe control options.
https://extension.psu.edu/japanese-knotweed
https://mnfi.anr.msu.edu/invasive-species/JapaneseKnotweedBCP.pdf
The best time to apply herbicide for control is in early fall when plants are moving nutrients from leaves down to the roots. As you will read, a combination of cutting and herbicides is most successful. This will take more than one season if you haven’t been removing flowers so that seed is not dropped.
As always, please read and follow all directions and precautions on any chemicals you use.
