Japanese knotweed – what you need to know when looking for your new home:

The words Japanese knotweed spark fear into property owners across the UK with stories about the cost of eradication, the damage it can do to buildings, driveways and gardens and the threat of being awarded an ASBO should you allow the invasive weed to grow onto your neighbours’ land. 


There is now thought to be an infestation of this invasive weed every few km in the UK but with particularly large pockets of difficult to treat growth in built up areas such as London, Cardiff and other major UK cities.


Japanese knotweed is a deciduous shrub that was introduced into the UK by the Victorians who considered it an attractive ornamental plant. What these pioneers had not appreciated was that Japanese Knotweed is deeply invasive, will spread relentlessly and will dominate native species. The roots of the plant can extend to 3m deep, and many meters across growing into building foundations and drains with the potential to cause serious structural damage.The plant can generate from a rhizome fragment as small is 0.7g (the size of your little finger nail) that can remain dormant in the soil for many years.

javanese knotweed summer growth

Control can be tackled in two main ways – through the use of chemicals in the growing season, or by “dig-out” methods which can take place at any time of the year. It is extremely difficult to eradicate and the home owner would be advised to approach a specialist removal company. It is impossible to give a ball park figure for the cost of this as it will depend on, amongst others, the size of the plant, the access to it and the methods to be used but an average infestation in an average UK garden could cost between £2,000 - £6,000.


The UK Environment Agency has described Japanese knotweed as:

"Indisputably the UK’s most aggressive, destructive and invasive plant"

How to identify Japanese knotweed?

In early Spring the plant pushes through with straight stems, reddish thenturning to green, and emerging heart shaped green leaves. It looks initially similar to asparagus.

Through the growing season Japanese knotweed can increase in volume by up to 1.2m per month, often reaching over 3m in hight. You will see long green stems and large green heart shaped leaves.

As the Summer progresses you will find purple speckles on the stems, and the plant will display small white flowers.

In Autumn, the leaves will turn yellow and fall from the plant, and in Winter all that is visible is the tall, bare and brown stems which some home owners cut back to ground level. The plant is not dead, it will regrow again in Spring. 

Estate Agents and Mortgage Lenders:

Estate Agents have an obligation under consumer protection regulations to advise any potential purchaser of any material facts that would affect the decision to buy. The presence of Japanese knotweed is considered to be “material” under these regulations. 


Equally, there is also now an obligation to disclose the presence of Japanese knotweed during the pre-contact enquiries made by Solicitors and failure to disclose could result in a legal claim of misrepresentation.


Many UK Mortgage Lenders will not lend against a property or land where Japanese knotweed is present and increasingly the majority of UK Mortgage Lenders will want to see evidence of a commitment by the current owner to fund and organise, in advance, a long term removal plan often referred to as a Japanese Knotweed Management Plan from a professional Japanese knotweed eradication company. In addition, many also insist that an Insurance Backed Guarantee is in place – this is to protect the lender in the case of the knotweedreemerging and the original eradication company – who should return to treat any regrowth - having ceased to trade.


Properly treated by a professional eradication firm Japanese knotweed does not have to be a deal breaker. Should you have a Japanese knotweed problem please contact me via email, phone or social media and we can talk you through your options in plain English, and help with all eradication alternatives.



For more advice, or if you have a Japanese knotweed issue, please contact me, Howard Downer, on:

info@t-c-m.co.uk, 01787 278086, tcmknotweedservices.co.uk and follow me on social media as:  


FB Doctor Knotweed at TCM Knotweed Services


Howard Downer has over 20 years’ experience in the invasive weed industry and is regarded by his peers as one of the most knowledgeable people within this field. TCM’s methodologies have been proven by extensive research and development and are now the industry standard.

Howard Downer & TCM have successfully completed projects for the London Olympics, the Commonwealth Games site in Scotland, Network Rail, Barratt Homes, Watkin Jones, Lovell Developments, Fairview Homes – and TCM continues to be the market leader in Japanese knotweed eradication.

November 21, 2017

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