Japanese Knotweed Removal

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Last Updated: 13/03/2022

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Japanese Knotweed Removal should be handled by professionals because of how extensive the problem can become and the issue of removing and destroying all traces of the plants' rhizomes. Because of the righteously fearsome reputation of Japanese Knotweed (click to find out more), as a house owner, you have to consider that there might be challenges when it comes to selling the property if it has been affected by it and how lenders will view the situation.

The cost to remove Japanese Knotweed is expensive which is why many people choose to use their own methods of removal and find that they are left with a battle as the weed keeps growing back: the 'DIY' method is not recommended unless you yourself are a knotweed removal professional.

What are the methods of Japanese Knotweed Removal?

Digging Japanese Knotweed out

This has to be done to exacting standards because it can cover a large area, including its large underground roots and it only requires 0.8g of a root for a new plant to grow again.

Additionally, the plant is classified as controlled waste under the Environmental Protection Act 1990 meaning it can ONLY be disposed of at licensed landfill sites with failure to do so putting you at risk of a huge fine or even imprisonment. This is a further reason to do this professionally as professionals will have indemnity insurance.

Professional Japanese Knotweed removers can also dig out the weed then dry it out and burn it on site or even bury it 5m deep.

Killing the plant with chemicals

Various chemicals can be used to kill Japanese Knotweed, particularly treatments which contain glyphosphate, but it can take some years - possibly 5 - to be sure you are finally rid of the plant. Professional repeated chemical treatment can cost £1,000s.

Biological Control

In 2010, experts introduced a Japanese bug (aphalara itadori) which feeds almost exclusively on the weed. The UK Government has now licensed this bug for this purpose, which is the first time the EU has sanctioned biological control of a weed.

Although biological control might cause the least long term disturbance of the habitat and ecosystem, it is likely to take years for the bug to make a serious impact and this is not a commercially available method of Japanese Knotweed removal at present.

What happens if you want to buy or sell a property affected by Japanese Knotweed?

If you are selling the property (or buying it) a mortgage lender will want to see evidence that there is a fully funded Knotweed Management Plan (KMP) including guarantee in place for a minimum of 5 years.

The KMP, issued by a Japanese Knotweed removal company, should include -

A Knotweed Survey – The survey drawing and findings accurately record the location and area of knotweed contamination and the level of risk it presents to the property.
A Treatment Guarantee Programme – A 5 year treatment and monitoring programme for the knotweed identified on the survey drawing and any knotweed if it emerges anywhere within the subject property.
Option to have a 5 year Guarantee – This gives you and the lender peace of mind that if there is any re-growth of knotweed within the property boundary during the guarantee period it will be treated at no extra charge.
A Completion Certificate – As soon as there has been 2 years without regrowth of knotweed your practitioner issues a completion certificate confirming the date that the treatment is complete.
Receipted Invoice – A copy of the receipted invoice confirming and providing evidence to the lender that the KMP is fully funded and that the work has commenced.
Bond Pay - This ensures that money you pay to the company is released to the company as and when it is needed according to the treatment plan.

How much does a Knotweed Management Plan cost?

This varies according to the specification of the plan. You can expect to pay around £1,000 for a 5-year plan, but if you want a further guarantee for 5 years after that, this is likely to cost around £1,500. To get comprehensive insurance that covers you for 10 years, you might have to pay up to £2,000.

Prices also depends on the size of the affected ground. The examples given would be applicable to ground of 50 metres squared or less: if your grounds are more expensive than this, you can expect to pay proportionally more.

What if I just want to get a property surveyed for Japanese Knotweed?

You can get a specialist survey to test for the presence of Japanese Knotweed for a few £100s - the exact quote figure depends on factors such as the scale of the property's grounds. Please fill out the Japanese Knotweed site survey quote form, which appears both above and below the following map. If you need to get an excavation quote, this is likely to cost around perhaps double this figure.

Written by: Andrew Boast

Andrew started his career in 2000 working within conveyancing solicitor firms and grew hands-on knowledge of a wide variety of conveyancing challenges and solutions. After helping in excess of 50,000 clients in his career, he uses all this experience within his article writing for SAM, mainstream media and his self published book How to Buy a House Without Killing Anyone.

Reviewed by: Caragh Bailey

Caragh is an excellent writer and copy editor of books, news articles and editorials. She has written extensively for SAM for a variety of conveyancing, survey, property law and mortgage-related articles.

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