How to Kill Japanese Knotweed

What is the most effective Japanese knotweed treatment?


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Why Kill Japanese Knotweed?

Japanese Knotweed is a fast growing invasive plant that can have disastrous consequences to the structural integrity of a property if left untreated. Knotweed can grow up at an alarming rate of 10cm per day and can exacerbate tiny gaps and cracks in masonry and concrete with its tenacious root system. This is why so many homeowners want to kill japanese knotweed as soon as they notice it growing on or anywhere near their property. 

Professional buyers and sellers of property are well aware of the damage knotweed can cuase and this has led to the plant reducing the value of effected properties by thousands of pounds. In 2018, Japanese Knotweed cost Britain an estimated £200 million. 

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Killing Japanese Knotweed

There are several methods to killing japanese knotweed depending on the resources at your disposal. Methods involve using weed killer for japanese knotweed, digging under the roots or the "wise" option, leaving it to the professionals to treat the troublesome plant. 

Weed Killer for Japanese Knotweed

Chemicals that will attack knotweed are actually available in your local garden centre. Glyphosate based products, like Round Up, are effective against japanese knotweed. These herbicides can either be sprayed onto the leaves or injected into the stem of the plant. The plant should be sprayed with weed killer at several stages during its growth. If you are attempting some DIY Japanese Knotweed treatment it should be noted that this is a hardy old plant and it will take several treatments over a number of growing seasons before you can effective say that your knotweed problem is under control - and even then describing it dead might be a streach. It is also important to ensure that any product you use to kill japanese knotweed is used correctly and safely.  

Professional treatment with chemicals is reccomended if you want to sell a property affected by knotweed for the following reasons:

  • Trained surveyors know how to use weed killer effcively
  • A professional treatment plan can allow you to sell the property before treatment is completed
  • japanese knotweed treatment guarantee may be required by your mortgage broker


The roots of Japanese Knotweed are known as "rhizome" and are one of the main culprits for the spread of the fast growing plant. Therfore, digging out rhizomes is the most immediate method of japanese knotweed treatment. However, it is also incredibly difficult to do so correctly as if even 0.8g of the roots aren't gathered, the plant can re-grow to its full size once again. 0.8g is the equivelant of the size of a fingernail and as the roots grow 3 metres deep and 7 metres in any direction, it is easier said than done to completely kill a patch of knotweed through excavation. 

Also, it is important to remember Japanese knotweed is classed as "controlled waste" so legally it must be disposed correctly at a registered landfill site. Failure do so could result in a fine or even prosecution from the Environment Agency. Homeowners are also liable if any knotweed grows onto neighbouring land so it's important to make sure you dispose of the weed correctly.

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Professional treatment - The Wise Choice 

In an ideal world, you could kill Japanese knotweed yourself over a nice weekend in the garden and not have to worry about the troublesome plant again. However, due to difficulty of treatment, the legal complications surrounding disposal of the plant and its potential to reduce the value of a property by thousands of pounds, it is much wiser to have Japanese knotweed professionally treated.

A professional surveyor will be able to give you expert advice on the most effective and affordable method of treating Japanese knotweed all the while saving you any of the hassle you may have faced attempting to kill japanese knotweed yourself.

Show us your Knotweed 

If you suspect you have Japanese Knotweed on or anywhere near your property, you can upload photos of the suspect plant for free and one of our expert surveyors will tell you whether or not it's Japanese knotweed. 

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Free knotweed photo assessment

Have you seen a suspicious plant and want to know if it is the dreaded Japanese knotweed? Simply click the button below to upload your photos and we will get back to you with an answer.

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If you suspect you have Japanese knotweed, then contact Wise Knotweed Solutions today on 0808 302 6636 to talk to an invasive plants expert or simply for some help and advice. 

Alternatively, click the button below to arrange a Japanese Knotweed survey and one of our knotweed experts will examine the suspect plant on your property. 

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