Japanese Knotweed

Japanese Knotweed is potentially as great a risk to property as flood for the conveyancing process; the speed at which the plant has spread, and continues to spread, throughout Britain is nothing less than spectacular. As a result, the Environment Agency describes Knotweed as ‘the UK’s most aggressive and destructive invasive plant’.

As featured in The Telegraph

Japanese Knotweed Hazard Alert

STL’s new and unique Japanese Knotweed Hazard Alert immediately informs you of the risk of Japanese Knotweed at residential properties when you order your usual property searches. This free alert automatically identifies if the risk is medium or high and is based on exclusive data from the Centre for Ecology & Hydrology

Japanese Knotweed Insurance Policy
Then, with just a couple of clicks, you can order an insurance policy to help protect your buyer and the lender in the event that Japanese Knotweed is identified on the property within 5 years. This highly affordable insurance is provided by CLS Risk Solutions and covers properties of up to 0.5 acres (larger properties quoted on application). It covers up to £20,000 towards financial loss if Japanese Knotweed is found at the property including:

  • Costs arising from a Japanese Knotweed survey
  • Remediation and repair work
  • Legal fees and expenses

The policy covers the buyer and successors in title, including any mortgagees, lessee or changes of the property or any part thereof

Download Product Card
Download Insurance Policy – Medium Risk
Download Insurance Policy – High Risk

Do you have a question about our Japanese Knowtweed Hazard Alert and Insurance Policy? If so, check out our FAQ page.


This highly invasive plant penetrates drains, paths and driveways, boundary/retaining walls, outbuildings, conservatories and gardens. Japanese Knotweed is therefore a serious and necessary consideration for conveyancers and this is reflected in the TA6 form question ‘is the property affected by Japanese Knotweed? (Yes / No / Not Known)’.

Japanese Knotweed: Did you know…

  • The Council of Mortgage Lenders (CML): Makes note of Japanese Knotweed as an environmental risk under contaminated land. They also state that valuers, inspecting property for mortgage purposes, must report to lenders where knotweed is present.
  • The Law Society Conveyancing Handbook refers to Japanese Knotweed under ‘Non-legal risks and liabilities’. Also the TA6 / Seller’s Questionnaire forms asks ‘is the property affected by Japanese Knotweed? (Yes /No/Not Known)’
  • The Society of Licensed Conveyancers (SLC) recognises the Invasive Non Native Species (INNS) Code. The INNS Code is regulated by the Property Codes Compliance Board (PCCB)
  • RICS Red Book guidance requires the valuer to indicate the presence of ‘invasive vegetation’
  • Classed as ‘controlled waste’ under the Environmental Protection Act 1990. It must be disposed at licensed landfill sites.
  • It is an offence to cause / allow the plant to spread in the wild under the Wildlife and Countryside Act 1981.
  • Under the Law of Nuisance and Third Party Litigation landowners can be sued if they fail to prevent knotweed from spreading to a neighbouring property.
  • The below ground rhizomes can spread up to 7m from the parent plant.
  • It can grow up to 4.5cm a day during Apr-Oct.