Do you have Japanese Knotweed in London?
Select Location
10%+
Property Devaluation
3m
Rhizome Depth
20cm
Daily Growth Rate
£166m
Annual UK Cost
The Risks of Japanese Knotweed in London
Japanese Knotweed is the UK's most destructive invasive plant. If left untreated on your property in London, it can cause serious financial and structural problems.
Property Devaluation
An infestation of Japanese Knotweed on your property in London could decrease its market value by 10% or more.
Structural Damage
Knotweed rhizomes can force through concrete, paving, drains and foundations — causing costly damage to homes across London.
Mortgage & Re-mortgage Issues
Most UK mortgage lenders will refuse a mortgage or re-mortgage on a London property unless a professional treatment plan is in place.
Neighbour Liability
If Knotweed spreads from your property to a neighbouring one in London, you could face legal claims for damages and removal costs.
Attention All Property Owners Across London!
Have you noticed Japanese Knotweed on your property? It can decrease your property value by 10% or more and cause problems with selling, re-mortgaging, getting a mortgage, or obtaining property insurance.
Japanese Knotweed in London — Advice from the Experts
What is Japanese Knotweed?
Native to Eastern Asia, Japanese Knotweed ( Fallopia japonica ) was brought to the UK in the 1850s as an ornamental garden plant. It has since become the country's most destructive non-native invasive species, affecting up to 950,000 properties across England and Wales.
Here in London, the plant thrives along the capital's extensive railway lines, riverbanks of the Thames, Victorian terraced housing and urban back gardens — all common features of the Greater London landscape. Its aggressive growth rate of up to 20cm per day and rhizome system that can extend 7 metres sideways and 3 metres deep make it extremely difficult to eradicate without professional help.
Japanese Knotweed costs the UK economy an estimated £166 million per year in treatment and property devaluations. We urge all homeowners and commercial property owners across London — from inner-city boroughs to the outer suburbs — to remain vigilant. You can check whether you live in a high-risk area using our live National Register.
How to Identify Japanese Knotweed in London
Japanese Knotweed changes appearance dramatically throughout the year, making it difficult to identify. Property owners in London should be vigilant in all seasons. Our extensive seasonal gallery provides detailed photographs, and our free identification service lets you submit photos for expert review within 30 minutes.
Identifying Japanese Knotweed Through the Seasons
Knotweed looks different depending on the time of year. Here's what to look for around your London property.
Spring
March – JuneRed/purple spear-like shoots emerge from mid-March. Stems grow rapidly, reaching over 1 metre within weeks.
Summer
June – SeptemberPlants reach 2–3 metres tall with dense foliage and bamboo-like stems. Creamy-white flowers appear in August.
Autumn
September – DecemberLeaves turn yellow, brown and orange before falling. Nutrients transfer down into the rhizome system.
Winter
December – MarchAbove-ground growth dies back, leaving hollow brown canes. Rhizomes remain alive underground, ready for spring.
What You Can Do Next
If you suspect Japanese Knotweed is present on or near your property in London, don't delay. The sooner you act, the easier and more affordable the treatment will be.
- Contact us on Freephone 03335 777 888 for free, no-obligation advice
- Email photos to contact@japaneseknotweedagency.co.uk for free identification within 30 minutes
- Book a professional site survey with one of our accredited specialists across Greater London
- Get a tailored treatment plan with an Insurance Backed Guarantee (IBG)
- Access legal support if the Knotweed has spread from neighbouring land
Free Identification & Expert Advice
The Japanese Knotweed Agency provides free identification and free expert advice. Our professional site surveys are competitively priced and include a full report. If treatment is needed, we refer you to an accredited removal specialist who provides their own quote — with no obligation.
If the Knotweed has spread from a neighbouring property, railway land or commercial site, our panel of specialist solicitors works on a No Win No Fee basis — so there are no upfront costs and no fees if your claim is unsuccessful.
Check Japanese Knotweed Sightings Near You
Our National Register contains over 23,000 unique records of confirmed Japanese Knotweed infestations across England and Wales. Check how many sightings have been recorded in London and surrounding areas.
Check the National RegisterOur Partners
Trusted by Clients Across the UK and Ireland
We work with property professionals, housing providers, local authorities, developers, and commercial organisations throughout the UK and Ireland, delivering expert Japanese Knotweed surveys, management plans, and remediation services with professionalism and reliability.
As Featured In
Recognised by leading publications and organisations across the UK
Mapping Knotweed Along Britain’s Rivers & Canals
We’re surveying waterways across the UK to map Japanese Knotweed infestations — 100% chemical-free, using our innovative thermo-electric remediation technology. Over 76,000 sightings mapped and counting.
Explore the Project100%
Chemical-Free
76k+
Sightings Mapped
Award Recognition 2026
Winner — International Green Apple Environment Awards 2026
Recognised for revolutionising invasive species management through chemical-free thermo-electric remediation. Presented at the House of Lords, Houses of Parliament.
Japanese Knotweed in London — Your Questions Answered
Here are some of the most common questions we receive from property owners across London.
Is Japanese Knotweed common in London?
Can I get a mortgage on a property in London with Japanese Knotweed?
How much does Japanese Knotweed treatment cost in London?
Is it illegal to have Japanese Knotweed on my property in London?
How do I report a Japanese Knotweed sighting in London?
Get in Touch About Japanese Knotweed in London
Whether you need free identification, a survey quote, or legal advice about Knotweed on your London property, our team is here to help. Fill in the form and we'll get back to you within 24 hours.