Japanese Knotweed and the property market

Japanese Knotweed has been described as the UK’s most destructive invasive plant, because its root systems often cause physical damage to man-made structures. It is a legal requirement to prevent its spread. The presence of Japanese Knotweed can affect property prices, and mortgage lenders may refuse applications if the plant is known at a site. Therefore estimating the risk from Japanese Knotweed to a property is clearly valuable.

Scientists from the UK Centre for Ecology & Hydrology (UKCEH), alongside partners in the Botanical Society of Britain and Ireland (BSBI) and the conveyancing company STL, developed a high-resolution model of Japanese Knotweed presence in Great Britain. Environmental data were combined with information on where the species occurs. The results from our predictive maps of Japanese Knotweed occurrence were combined with the data from actual Knotweed localities to produce a risk model covering every postcode in Britain. 

Our datasets and risk model have also been incorporated into a ‘hazard alert’ for Japanese Knotweed, currently offered by the conveyancers STL, who first helped to identify the need for such a product. We are also working to license our datasets and risk model to other conveyancing search providers. The product has the potential to help home-buyers, lawyers working in conveyancing and mortgage lenders to make decisions about the risk from Japanese Knotweed at any particular location. Such information should assist with subsequent decisions on the need for insurance or site surveys. Regular updates to the datasets underlying the hazard alert will ensure that the risk model remains appropriate and up-to-date.

Japanese Knotweed is a serious and necessary consideration for conveyancers and we are pleased to offer this new hazard alert service thanks to the input from our scientific partners.

Alan Thorogood
CEO of STL Group

BSBI volunteers have been recording the spread of Japanese knotweed since it was first recorded in the wild in 1886: this has formed the basis for a substantial body of research into its ecology, spread and invasiveness. Although still relatively uncommon in the wild, it can become very abundant in the right sort of habitat (disturbed places close to habitation), where it spreads through the dispersal of root fragments (usually in dumped soil). In these locations, it can exclude all other plants species and cause physical damage to man-made structures such as pavements, walls, foundations and roads.

Dr Kevin Walker
Head of Science at BSBI

Home buyers and owners, mortgage lenders and conveyancing search providers

Data sets and hazard alerts for Japanese Knotweed

Informing home buyers and owners, mortgage lenders and conveyance search providers about the risk of Japanese Knotweed presence and enabling evidence-based decision making