Hi there. I just moved in to a new house and there’s an area of the backyard filled with knotweed. I’ve been cutting and pulling it out, but I just read that I should spray it instead. Is that really the best option? Where do I go from here?
Clatsop County Oregon
Hi and thank you for your questions regarding Japanese knotweed. It sounds like you have been busy attempting to remove this noxious weed from an area in your backyard.
Yes, you are correct; cutting and pulling is strongly discouraged, as doing so only encourages denser new growth. I recommend checking out this free publication from OSU Extension Service titled Biology and Management of Knotweeds in Oregon: A Guide for Gardeners and Small-Acreage Landowners: https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em9031.pdf. I am not a licensed pesticide applicator, so I am unable to recommend a specific chemical treatment. However, this publication goes over in detail some options available to you. Check it out! It contains a lot of useful information.
I also recommend reaching out to the Clatsop Soil and Water Conservation District for assistance. Japanese knotweed is classified as a noxious weed and therefore they can provide free technical assistance. Find out more here: http://clatsopswcd.org/?page_id=1004. You can also call them at 503-325-4571 or email email@example.com.
I wish you the best of luck with these efforts, and let me know how things work out!