Japanese knotweed

What is Japanese knotweed?

The Japanese knotweed is a perennial plant originally from Asia.

Although it is known for its medicinal properties, in Belgium it is considered a weed and is widely distributed throughout Wallonia.

Asian knotweeds survive the winter through the underground buds on their rhizomes. 

In spring, these plants grow very quickly and their aerial stems can grow more than 10 cm per day. The rhizomes can grow up to 1 m per year and can spread laterally for more than 5 m around the aerial stems. They sink up to 2 m deep into the ground, sometimes more (landfill).

Why is it considered harmful?

Apart from the fact that the plants are dense and disrupt road and waterway maintenance, Japanese knotweed is a threat to biodiversity as it grows very fast and prevents indigenous vegetation from developing.

How can you get rid of it?

Japanese knotweed is difficult to eliminate owing to its high growth rate and high regeneration capacity. 

Although certain techniques exist to control this plant, they only rarely serve to eliminate it permanently. It is sometimes preferable not to take action if these plants are not an obvious nuisance, because although they grow rapidly, knotweeds rarely produce viable seeds; they reproduce mainly by cuttings from stem fragments or pieces of rhizome. These are most often produced by management related to roadside maintenance and ground movement.

However, a methodological decision tree has been developed by the CiEi (Interdepartmental Invasive Species Unit) in the event removal is called for.

Which treatments does your contaminated soil require?

The methods of treatment/development of land contaminated by Asian knotweed propagules are currently as follows:

The transport of contaminated soil also requires special arrangements to be in place:

It is also recommended to avoid moving around in the vicinity of an area contaminated by invasive plants as much as possible. Any construction equipment that has come into contact with soil contaminated with invasive plants must be washed before leaving the site. Special attention must be paid to the wheels and/or tracks.

Japanese knotweed rhizome


What about adding ABV?

Thanks to their experience, ABV Environment experts can easily help you identify knotweed, advise you on the best way to take action if necessary and estimate the cost of cleaning up your land contaminated by rhizomes. The work of our experts will also involve checking whether your contaminated land is properly evacuated as well as attesting to the absence of residual rhizomes on the rest of your land.

Please feel free to get in touch with us! With or without knots, your project must be a success!


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