Glossary · UK
What is Japanese Knotweed?
An invasive plant whose presence near a property can damage structures, reduce value, and complicate mortgage lending and a sale.
Full Definition
Japanese knotweed is a fast-growing invasive plant that can spread through underground roots (rhizomes), potentially damaging foundations, drains, walls and hard surfaces. In the UK it matters chiefly to property buyers, sellers and lenders. Sellers must disclose its known presence on the standard TA6 property information form, and failing to do so can lead to a misrepresentation claim. Many mortgage lenders will refuse to lend, or require a professional treatment plan with an insurance-backed guarantee (often spanning several years), before approving a loan. It is not illegal to have knotweed on your land, but allowing it to spread onto neighbouring property can result in civil liability or action under anti-social behaviour powers. Treatment usually involves herbicide programmes or excavation, and remediation costs can be significant. Because of its effect on saleability, valuation and mortgageability, knotweed is a key issue to identify during surveys and conveyancing before committing to a purchase.