Towards the end of the 19th century, the knotweed was imported from Japan in order to be planted in this country as a rich forage crop for wild animals. These have not accepted the unknown plant to this day, but the giant knotweed has mutated into a plague that is difficult to combat in many areas of the country.
The Japanese knotweed should definitely be removed before flowering so that it cannot multiply any further
Mechanical methods - laborious but effective
The problem is not so much the Japanese knotweed's rapid and profuse growth as its sheer spread. The plant is a deep-rooter, which also sprouts from its rhizomes every year. In addition, it is able to generate its own offshoots from shoot axes - i.e. even the smallest root parts. Control is therefore only successful if all parts of the plant, including microscopically small ones, are carefully disposed of.
Completely remove the overgrown area
If you want to be on the safe side, there is only one radical measure that can be taken: Cut the plants down to just above the ground and burn the parts of the plants. Then dig out the entire overgrown area to a depth of about three meters - and dispose of the entire excavation. In order to render harmless any root parts that may have remained deeper, put a plastic film on the bottom of the pit. Fill in new topsoil on top.
mowing or grazing
If you don't want to be quite so radical, get some sheep and/or goats. After some time getting used to these four-legged lawnmowers, they will eat up the Japanese knotweed, although the roots remain in the ground. However, these die off after a few years if the plant is repeatedly prevented from growing again. If animals are not desired, mow the vegetation every two weeks with a lawnmower - but be careful: it must be cleaned thoroughly afterwards!
Cover with foil
Also tedious, but often successful is the covering of the overgrown area with a thick, black foil, which takes place in addition to keeping it short - this simply ensures that the plant starves to death from the ground up.
Tearing out / digging out
If you have only found a few shoots of the Japanese knotweed so far: pull them out or dig them up again and again!
tips
Many gardeners swear by broad spectrum herbicides, which are best injected directly into the rootstock, to remove Japanese knotweed. However, please bear 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.