A study by Horticulture.co.uk has indicated that over the last 5 years, cases of Japanese Knotweed have increased by a national average of 27.91%. They have also produced an interactive map searchable by postcode to show live and resolved cases by area: Click here
A YouGov survey of homeowners in July last year suggested 80% of potential buyers would walk away from buying a property affected by Knotweed and even if they were still considering the purchase they would expect a discount of 5-10% on the asking price.
Dean Wilson of Horticulture.co.uk commented: “When instructing a surveyor for your new home purchase, always ask them to look for Japanese Knotweed and other invasive plants.”
“This is especially important if the property borders an old or existing railway line, or is close to a river, canal or stream where the plant is known to spread via small fragments of root that work their way downstream.”
The non-indigenous plant was originally introduced from Japan in the 1800s to stabilise railway embankments and to make them look more attractive. Unfortunately, it can grow 10cm per day and can cause structural damage and crowding-out of native species. The plant is particularly difficult to remove due to its complex root systems.
Although it is not illegal to have the plant on your property, it is against the law to allow it to spread into the wild or onto a neighbouring property. Homeowners who allow this to happen can be fined or taken to court.
Below is a table breaking down the 29,536 confirmed cases and the regions with the greatest increase in the last 5 years: