There are few plants that can cause as much hassle and angst as japanese knotweed. It’s an indomitable scourge, one of the most invasive species on the planet and can grow with alarming speed to choke out native vegetation and damage structures like driveways, walls and railway lines.
Knotweed can be difficult to remove completely and even small clumps of the plant can cause problems. As a result, mortgage lenders are wary of lending against properties where Japanese knotweed is present and it can be very expensive to buy a property with an established Japanese knotweed problem that will require extensive treatment or complete removal.
However, there are steps that can be taken to reduce the problem. For example, a Japanese knotweed risk assessment can be carried out by an approved japanese knotweed specialist and an appropriate treatment programme can then be put in place. For larger infestations it may be necessary to have the site excavated and removed. This is a more expensive approach but it offers the best chance of eradicating the knotweed and ensuring that it cannot return.
In addition, a registered company can produce an insurance-backed guarantee to provide peace of mind that the knotweed will be eradicated and that the insurer will cover any resulting costs if it does occur. This means that buyers and developers can be confident that if they follow the correct procedures they will be able to get their mortgage and avoid expensive legal disputes with lenders over Japanese knotweed at a later date.
Small weed clumps are often easily controlled by digging or spraying with a weed killer but for large sites it’s essential to find a qualified and accredited japanese knotweed specialist. These companies can draw up a risk report and offer treatment plans with a guarantee of complete eradication, which are often accepted by mortgage lenders.
A recent development in the fight against Japanese knotweed is the release of a biological control insect. Aphalara itadori, a 2mm-long psyllid plant louse from Japan that has been shown to feed on knotweed, is thought to suppress its growth and may reduce the need for chemical controls. It’s not currently available to the public but is being tested in a number of areas.
The Royal Institution of Chartered Surveyors has worked with the PCA Invasive Weed Control Group to create a list of vetted Japanese knotweed specialists and the Association of Professional Landscapers has a ‘Find a Tradesman’ service that includes invasive weed control. In addition, the National Plant Protection Organisation keeps a database of vetted contractors. However, it’s always worth checking references before hiring a contractor to carry out any work. This is especially important for larger projects such as site excavations and construction works.