A Homeowner’s Guide to Controlling Japanese Knotweed


Although Japanese knotweed was initially brought to Europe as an ornament, it is something that you do not want to grow in your gardens. These plants are tenacious and invasive. Japanese knotweed is a big problem for property owners because it can grow up to 20 cm every day.

Aside from its incredible growth rate, these plants can even grow through tarmac and concrete. If you cut it down, it will just sprout because its roots can do down up to 3 meters deep. While Japanese knotweed does not produce seeds, it can grow from even the smallest fragments of rhizomes.

Rhizomes are the underground network of stems and roots. This means that Japanese knotweed spreads easily. If left unattended, Japanese knotweed is almost impossible to control. It acts like a monster – devouring any property. In fact, there are homeowners who have been told that it would be cheaper to tear their house and rebuild it rather than treating the knotweed problem.

If you do not want to tear down something and rebuild it again, it is time that you learn japanese knotweed control. Here are some control measures that you should consider:

Chemical treatment

If you want immediate control measure, you should consider chemical treatment or herbicide. For Japanese knotweed, the recommended products are called glyphosate-based herbicides. For glyphosate-based herbicides, water should be mixed before applying.

You can directly spray the herbicide to the leaves or you can inject it into the canes but before anything, you need to cut back the plant stems. The best time to spray the leaves is late summer or early fall. There are some gardeners who spray herbicide repeatedly throughout the growing season to ensure that the plants never get a chance to sprout.

Smother through tarps

The simplest method is getting a poly tarp to cover the patches. For this, you need to invest in tarps. By using tarps, you are not allowing the sunlight to penetrate the seams. Before anything, you need to cut the weed canes and remove the loose material. It is better to cover the plants in spring to keep the weed from growing.

Cutting and digging up

Cutting and digging Japanese knotweed can sound laborious but these are effective when it comes to controlling the plant. After cutting the weed, you can start digging it. Digging should be considered because Japanese knotweed root systems are extensive. By digging, you are getting rid of the underground shoots.

However, you need to be careful. Any waste that contains the plant must be disposed of properly. You can consider taking it to the landfill but you have to contact appropriate specialised carrier. Do not think about compost waste because it can survive the process. More importantly, do not expect immediate results.

Moving forward

When all else fails, you have to call the professionals. The good news is that there are many companies that offer services when it comes to controlling or removing Japanese knotweed. The key here is to find the right one. To help you get started, you should check out the British Association of Landscape Industries. The website will show a list of companies recommended by the Royal Horticultural Society.