Towards the end of the 19th century, knotweed was imported from Japan to be planted in this country as a productive food plant for wild animals. To date, these have not accepted the unknown plant, but in many areas the giant knotweed has mutated into a pest that is difficult to control.
How to remove Japanese knotweed?
There are various methods available to effectively remove Japanese knotweed: radically remove the growth, mow regularly or graze with animals, cover the area with foil, or pull out or dig up individual shoots. Please note that all plant parts must be disposed of carefully.
Mechanical methods – complex but effective
The problem lies less with the rapid and lush growth of Japanese knotweed, but rather with its sheer spread. The plant is a deep-rooted plant that also sprouts from its rhizomes every year. It is also able to generate offshoots from shoot axes - even the smallest root parts. Therefore, control is only successful if all parts of the plant, including microscopic ones, are carefully disposed of.
Completely remove overgrown area
If you want to be on the safe side, only one radical measure can help: cut the plants down to just above the ground and, best of all, burn the plant parts. Then excavate the entire overgrown area to a depth of around three meters - and dispose of the entire excavation. In order to render any root parts that may remain deeper harmless, a plastic film is placed on the bottom of the pit. Fill in new topsoil on top.
Mowing or grazing
If you don't want to go quite so radically, then get a few sheep and/or goats. After some time of getting used to it, these four-legged lawn mowers will eat up the Japanese knotweed, although the roots will remain in the ground. However, these die after a few years if the plant is repeatedly prevented from sprouting again. If animals are not desired, mow the vegetation briefly every two weeks with a lawnmower - but be careful: it must be cleaned thoroughly afterwards!
Cover with foil
Also tedious but often successful is covering the overgrown area with a thick, black film (€34.00 on Amazon) in addition to keeping it short - this simply ensures that the plant starves from the ground up.
Tear out / dig up
If you have only found a few shoots of Japanese knotweed so far: pull them out or dig them up immediately and again and again!
Tip
Many gardeners swear by broad-spectrum herbicides when removing Japanese knotweed, which are best injected directly into the rootstock. However, please keep in mind that Roundup & Co. are generally not approved for private use and therefore require approval. They also harm the environment, microorganisms, insects and yourself.
