For one of the most invasive plants, Japanese Knotweed Removal can be very difficult. These plants were introduced from Japan into the UK and them to North America in the 19th century. It was used as an ornamental for landscaping but it spread terribly. They like warm and moist areas, riverbanks, roadsides and gardens. They will often spread with landfill being moved, all it takes is a section of root for it to grow.
The knotweed will not grown in forested areas as they tend to be too dark. In the right conditions, however, they will take over. They are so hardy that they will grow through the cracks of a sidewalk or driveway.
One of the first things you can do is to throw a tarp over the plants to prevent sunlight from getting to them. This will smother them and they will not have the nutrients to grow. You must make sure that the tarp is large enough to cover the plants and then some area and that it is weighted down with heavy objects so that no sun can get to the plants.
At this point you can leave the tarp there indefinitely and mulch over the top of it and put some decorative pots or a table and chairs in the space. You can also create raised beds as the plant will not be able to come through the plastic or poly material of the tarp that you have used. You can also throw an old carpet over the plants if you have a piece that is large enough to smother them.
Japanese Knotweed Expert Ltd say that weed killer is another method that works well for killing off knotweed. The active ingredient in the following brands is glyphosate, look for Touchdown, Rodeo, Pondmaster, Landmaster, Ranger or Roundup. As Roundup is the most well know, it works systemically to kill the plant after the leaves have been sprayed. It can also be administered into the roots by injection.
Persistent cutting can be effective but you must make sure to pick up all the cuttings or they will root and cause even more of a problem. Cutting can be done before spraying and covering with a tarp. It is a lot of work to get rid of this plant and you have to be aggressive about it.
A good thing to do is dig the plant up and remove the root system. You will need to make sure you do this a couple of times to get everything removed. Then spray the area and even put a tarp over it just to make sure. Japanese Knotweed removal is a big job that requires persistence and a lot of work.
Another effective removal method is excavation and burial. It must be buried to landfill site which is licensed. Excavation involves digging the whole plant with its root system which is very costly.
A root barrier is another way to remove the stubborn Japanese knotweed. The creation of a barrier would confine the weed to a certain perimeter. Soil sifting is also effective in removing the Japanese knotweed where the soil is excavated mechanically before sifting through to separate it from the weed.