What is it?
Japanese knotweed is an invasive, non-native plant that can cause physical damage to buildings and land, which in turn affects the value of the property, and can be expensive and difficult to eradicate or treat.
The Government has issued guidance on invasive plants such as Japanese knotweed, and it states that not only have you got to prevent invasive non-native plants spreading on your land, you also must prevent harmful weeds on your land spreading onto a neighbour’s property. You can be fined up to £5,000 or sent to prison for up to 2 years if you allow contaminated soil or plant material from any waste you transfer to spread into the wild. The most commonly found invasive non-native species are:
- Japanese knotweed
- Giant hogweed
- Himalayan balsam
- Rhododendron ponticum
- New Zealand pigmyweed.
For more information on how to identify these and what to do if you do find it, read the Government guidance.
Why is it a big deal?
When you are buying a property, you will receive a Property Information Form filled in by the seller. There is a standard protocol question on whether the property has been affected by Japanese knotweed and if so, whether there is a management plan in place. The form does not ask about other invasive plants.
However if the seller states there is not Japanese knotweed and there is, this may not necessarily be relied upon.
Building insurance may not cover for Japanese knotweed if it is found. Usually policies state the owner has to do everything they can to prevent damage to a home, and ignoring the presence of a plant may mean that any claim is denied.
Some mortgage lenders have made changes to their requirements for Japanese knotweed. For example, Coventry Building Society need to be informed if there is Japanese knotweed present within the boundaries of the property and is within 7 metres from a habitable space or that it is causing damage to outbuildings, structures, drains, paths, boundaries walls, or fences.
The recent case of Williams v Network Rail Infrastructure Ltd  EWCA Civ 1514 shows that the Court of Appeal accept that Japanese knotweed is a serious issue and this could raise further claims. In this case, the claimants were owners of two semi-detached bungalows in Wales that backed onto a railway embankment which had been infested by Japanese knotweed. The claimants brought a claim of private nuisance against Network Rail. The Court of Appeal decided that Japanese knotweed can be an actionable nuisance.
If you are concerned about Japanese knotweed on the property you are purchasing or a neighbouring property, then talk to your solicitor. There are a range of options available, including indemnity insurance, or having a specialist knotweed survey and assessment. If any work has been done to Japanese knotweed to eradicate it, it is worth considering using a specialist company that will provide a guarantee.