I live in the suburbs of Copenhagen, close to a lake which is a popular site for leisure activities. Unfortunately Japanese knotweed is taking over the landscape and shores of the lake. Local authorities are considering to allow the use of round up, allthough they have forbidden the use of chemicals in both private and public gardens. What is permaculture’s take on this?
It IS edible and has lots of uses. Knotweed grows strongly here in the Pacific Northwest too, Annette. Many consider it a pest…permaculturists, well, not so much. They use it for a lot of things (you’ll have to do your own research on that), pull it up in small areas if they want to say, grow a few fruit trees or a small vegetable garden, graze it with goats (that works really well), or try to change the conditions in some way, say by getting trees to grow that make shade. People blame the plants and want to eliminate them. The plants did not appear specifically to torment human beings. They are simply responding to conditions. What people should be thinking when they see Japanese knotweed everywhere is wow, we really messed up here. Instead, they do what they do best, go to war. Permaculture tries to find gentler methods, and using synthetic herbicides violates the ethics, therefore, we find another way. It’s really about adjusting one’s thinking.
Yes I completely agree with Larry. If you truly do want to get rid of it. The only reasonable ways are to outcompete it. Growing strong shading trees will diminish it’s growth with competition. knotweed are incredibly persistent plants repeatedly cutting won’t kill them or in even slow down their spread. The other less “permaculture” solution is to simply cut back just before they flower and cover with a black tarp strangling them with lack of light. Make sure the tarp does not allow any light through and that you inspect it for holes for 2 to 3 weeks during the knotweeds optimum growing season. This solution is only feasible if you only have a small patch.
Unfortunately unless the plant is small uprooting them is not really a solution.