Whilst Japanese Knotweed is not yet set on world domination, it is causing some considerable problems in the Housing Market. Failure to treat knotweed can lead to an Antisocial Behaviour Order (“ASBO”).

Fallopia japonica, commonly known as Japanese Knotweed, is a large, herbaceous perennial plant native to East Asia in Japan, China and Korea. In North America and Europe the plant has been classified as an invasive species in several countries and in Australia it is illegal to have any of this species growing on your property.

Described by the Royal Horticultural Society as a “real thug”, the plant grows at up to 10 centimetres a day, up to 3 metres high and has a root system of up to 7 metres, which can grow under concrete, tarmac and can damage drains, underground cables and house foundations. Its spores can lie dormant for many years. It’s estimated that it causes £166,000,000 of damage a year.

It can and does cause housing transactions not to proceed, usually being spotted by a building society valuer during the lenders survey. The standard property information also asks the sellers to declare if the property is affected by the plant. Treatment is expensive, with a relatively small area costing in excess of £1,500 to treat by the increasing number of specialist firm offering this service. Larger affected areas can be subject to a long term management plan, especially where it affects apartment blocks and common areas.

If you are considering marketing your property, or you are concerned that a property that you are buying is affected, it is essential to have an early professional survey. Some lenders will not lend if a property is affected, whereas others will only lend once professional treatment schemes are implemented. Dealing with this issue early in a transaction is essential if delays and unforeseen costs are to be avoided. Some insurance companies are beginning to offer policies against the cost of treatment.