Knotweed News

How To Kill Japanese Knotweed The Experts Guide

Author: Site Admin

Date Posted: Tuesday 26th October 2021


Our Step by Step Japanese knotweed removal process

  1. Identify the Japanese knotweed
  2. Send a photo to JKSL for FREE confirmation
  3. Wait for the JKSL site team to come and inspect
  4. JKSL will provide a range of treatment options, bespoke to your sites requirements
  5. Get a quote, we’ll provide a detailed price breakdown. We include on going monitoring programmes and insurance backed guarantees
  6. Our experienced in-house team will carry out the treatment to the highest standards
  7. We provide a range of treatment solutions. From herbicide application to excavation and removal or burial

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This invasive plant has been known to impact entire gardens, properties, development sites, and cause thousands of pounds worth of damage to buildings and underground utilities when it hasn’t been eradicated early enough. Fully exterminating the weed has proved difficult due to the extensive rhizome network of roots associated with the plant, this is why you need expert advice on how to kill Japanese Knotweed.

Japanese knotweed is capable of growing rapidly in most environments and on average can grow some 4cm per day (and as much as 10-12cm per day in summer), resulting in a dense infestation in only a couple of weeks. More so, it only takes a small fragment of root or rhizome for the plant to grow and establish itself, either on a new or existing site. Knotweed fragments can be transported through soil importation, during construction, or even carried by footwear. Fortunately, with consistent and persistent efforts Japanese knotweed can be eliminated.

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Yes, it can be removed using herbicides but herbicide treatments do take time to work, and chemical treatments for Japanese knotweed control can take around 5 years. This is one of many methods used to Kill Japanese Knotweed. Chemical treatment is considered the most cost-effective method and is favoured by domestic premises where the time factor for treatment may not be quite as important, say when compared with a development site where swift removal may be of vital importance so as not to hold up a building project.

But it’s advisable to spray the Japanese knotweed through various stages of the plant’s development during the growing season. The infestation size, the presence of watercourses, and the general public all have to be considered during herbicide selection.

So, what chemical products can be used for Japanese knotweed treatments?

Herbicides, including Glyphosate based products, are highly effective at eradicating this notorious plant. Glyphosate based herbicides are applied on the foliage of the weed using a sprayer after being mixed in a tank. The Glyphosate herbicide can also be injected into the stem. This method is most suitable for ecologically sensitive areas where spraying is not suitable.

How often should you spray Japanese knotweed?

The best time to spray the leaves of Japanese Knotweed with herbicide is late summer or early autumn, when the plant is in full growth. During this period, the plant will be flowering and by spraying the foliage helps draw more nutrients, and the chemical spray to the rhizome, during the period where the plant would usually build its food reserves. Over time this will weaken and eventually kill off the plant, although repeat spraying could be required over multiple years to be fully effective.

By spraying Japanese knotweed at the right time will boost effectiveness as the herbicides travel down to reach the parts of the plant that are deep underground. While it will not kill off the plant after the first few sprayings, repeating the treatment over a number of years will have the desired effect.

How long does it take to remove Japanese knotweed?

Full treatment of Japanese Knotweed varies in time span depending on the extent of the infestation and the method that is chosen to remove it. The quickest though most expensive method is through excavation, which involves digging it up out of the ground, and is usually very effective when carried out by a professional Japanese knotweed removal company.

The most commonly chosen and cost-effective method of Knotweed removal is chemical treatments, but this type of knotweed treatment can take several years, sometimes as many as 5 years, to completely eliminate the plant. This method therefore requires spraying of the Knotweed each year at the point when the plant is at its full growth for that growing season. This should be handled by a recognised Knotweed company, using the right strength of herbicide, rather than tackled via your own DIY Knotweed removal method


Rhizomes digging is a highly effective but more costly method of Knotweed removal since it requires large amounts of soil removal over a wide area. It is usually the preferred option for those requiring a quick solution, such as developers, rather than for domestic gardens where it isn’t deemed necessary.

But how does it work?

Rhizomes (the extensive network of underground roots) are very proactive in the spreading of Japanese knotweed. Therefore, excavating the rhizome fully and either disposing them to a licensed landfill facility or an alternative mechanical remediation strategy is one of the best ways of removing the plant. It is essential to ensure that all the pieces have been removed and a clean site policy is implemented to prevent cross-contamination.


Chipping Japanese knotweed can be used as means of disposing of the stem cuttings to improve aesthetics and to facilitate access to the infestations. However, it is important to ensure that the cuttings have sufficiently dried out before being chipped to prevent regrowth. Ideally, these works should be undertaken within the winter period. Chipping on-site should be done in a controlled way to avoid cross contamination.

How can Japanese knotweed stems be disposed of?

Chipping on-site has replaced on-site incineration as a more environmentally friendly method of disposal. If the stems are to be chipped, it is vital that this is done in the winter months once the stems have died and dried to make sure they have no chance of spreading or regrowing.


The MeshTech method is an eco-friendly means of controlling the spread of Japanese knotweed. Designed by Dr Eric Connelly and JKSL, the method does not use any chemicals, and therefore leaves the lowest possible on-site footprint where it is used. It is also useful in preserving soil fertility and controlling soil erosion, especially along river banks.

MeshTech is effective as it forces the plant to sever its own stems on a wire mesh placed over it where it grows. This exposes the plant, leaving it open to damage by frost and rot. Eventually, the Knotweed plant will die off due to exhaustion of the nutrient stores in its root system.

What eco-friendly ways are there for Japanese knotweed treatment?

MeshTech can be a preferred methodology over herbicide use because it ensures that the surrounding environment remains as unaffected as it can be, conserving animal and plant life. It is an ideal deal technique for Japanese knotweed removal & eradication in ecologically sensitive areas such as riverside locations, railway embankments, and highways.


Although still being trialed, the biological method is one of the environmentally-friendly methods of how to kill Japanese knotweed. This method of control relies on the use of a tiny sap-sucking insect called the psyllid, which lays its eggs on Knotweed. The young nymphs eat the plants, preventing them from growing any taller, and this drains the life out of the weed.

JKSL closely follows the research work of CABI (Centre for Agriculture and Biosciences International) and DEFRA (The Department for Environment, Food and Rural Affairs), who began the psyllid release programme way back in Spring 2010 at several sites across England and Wales. A natural predator, the psyllids insect, has been discovered as a method of naturally keeping the plant under control.

Can biological methods be used for getting Japanese Knotweed removal?

Biological control will not kill Japanese knotweed but can slow the spread of the plant and make it more vulnerable to chemical control. The risk of damage to native plant species has been found to be low, meaning it could open the door to more biological control against Japanese knotweed and other invasive weeds. The hope is that the insects could eventually establish themselves across the nation to slow the spread of Knotweed.


There are several methods of Japanese knotweed treatment that are successful. (Find out more about potential Japanese knotweed removal costs.) Eliminating the weed often requires a multi-pronged approach by applying different methodologies.

Whether you choose chemical or mechanical methods of getting rid of Japanese knotweed, the job should always be handled by professional Knotweed removal experts. Often, hiring a professional service such as JKSL for Japanese knotweed removal is the only way that you can be sure the weed and its roots have been completely eradicated.

If you are still unsure of the best method of Japanese knotweed removal for you, then get in touch with JKSL. We can help you with Japanese knotweed identification to determine if you have a problem, and then give you advice on the Japanese knotweed treatment options best suited to your particular situation.

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I believe I have a Japanese knotweed infestation.
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