How to eradicate Japanese knotweed

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Methods of Eradication Japanese Knotweed

It’s a notoriously fierce weed that can grow up to 4cm a day, quickly infesting land and property – but why is it so important to eradicate Japanese knotweed?

Once a Japanese knotweed infestation takes hold it poses a very real threat to the structural integrity of a property, which can then lead to problems later when it comes to mortgages and selling. It also comes down to the property owners who have noticed a knotweed problem to ensure the knotweed doesn’t begin to encroach on neighbouring land or properties. 

Japanese knotweed is a serious problem that should be tackled head-on, if not you’ll be leaving the weed to grow stronger and harder to treat. When it comes to how to eradicate Japanese knotweed, methods will usually depend on the location, the time-frame and the budget, and range from chemical extractions to traditional excavation. 

Although many find it tempting to dig the weed themselves, this usually makes the problem worse and can lead to further spreading. This article covers all of the potential methods that are effective, helping you choose the right one for your situation.


Chemical treatment

Also known as herbicide, chemical treatment for Japanese knotweed is typically the most cost-effective method of eradication. This method involves using preparation methods throughout the plant’s dormant months, such as flattening dead canes, before later spraying the foliage with a chemical treatment or injected herbicide into root stems. However, this is not the quickest option available as the process involves several treatments over the course of around 24 months, but sometimes longer.



This is a far quicker solution than chemical treatment, and often popular in cases where time is of the essence. This method involves a professional excavation of the knotweed, followed by the contaminated material being taken to a designated landfill where the plant cannot survive or reproduce. Clean material is then used to backfill the area that was excavated.



This is a method exclusive to JKQ that takes a different approach to eradicating Japanese knotweed. Meshtech is a patented technology devised by Dr. Eric Donnelly alongside JKQ. This method forces the knotweed to press against the mesh and sever its own stems, also exposing the plant to frost and rot, working to weaken the plant and drive it to its eventual death. 

Meshtech is more environmentally-friendly than other options such as chemical treatment, involving no chemical involvement and minimal ground impact. This method also comes at a lower cost than removal to landfill and is more attractive to those concerned with causing little disturbance to the surrounding land and wildlife.


Other methods for eradicating Japanese knotweed

Composting offers a lower-cost treatment and recycling option for your knotweed. The method uses the appropriate heat to cause a cellular breakdown in the plant, however, it should be noted that this method has the potential to increase spreading rather than eradicate it. 

On-site chipping is another method of eradicating Japanese knotweed that is being used as a more environmentally-considerate replacement for on-site incineration. This method involves controlled chipping of knotweed stands, carried out once they have completely dried out, and it offers a minimised risk of cross-contamination. 

Lastly, biological treatments are currently being trialled as a potentially eco-friendly option for eradication, using Japanese knotweed’s natural predators such as psyllid insects – which could be an option in the near future.


Best time of year to tackle the problem

When it comes to the best time of year to tackle your Japanese knotweed infestation, it will largely depend on the treatment method you choose. In general, the summer months are regarded as the most effective time for eradication as the plant is in flower and actively absorbing the most nutrients in its roots. However, chemical treatments are often best sprayed directly onto foliage in autumn. The winter months are when Japanese knotweed lies dormant, and despite out of sight often meaning out of mind, this is a great time to catch the problem while it isn’t growing.


How long the knotweed removal process takes

The length of time it takes to eradicate knotweed will vary depending on which treatment you choose. Excavation and on-site incineration methods are generally the quickest solutions, taking a number of weeks to take care of your problem. Chemical treatments, however, will take around 2-5 years, but are the most cost-effective option.

When it comes to how to eradicate Japanese knotweed, there are a considerable amount of options to choose from, each offering different benefits to different knotweed, lifestyle and ethical circumstances. The most effective methods often apply more than one option in a multi-pronged approach that nips the problem in the bud. For more information about which method of eradication is right for you, JKQ offers expert advice on identifying Japanese knotweed and the best option for its removal.