Japanese Knotweed

David Percival, a property lawyer at Spire Solicitors LLP, discusses the problems associated with Japanese Knotweed when buying or selling a home.

Whether selling or buying a home, one of the greatest potential problem may be a plant growing in the garden.

David Percival

What is Japanese Knotweed?

Japanese Knotweed is native to East Asia and was first introduced to British gardens in Victorian times. It grows from small shoots which can then grow up to 3-4 metres in height and looks a little like bamboo but with more of a red or green colour. It has light green leaves and small white or cream flowers that usually appear in summer.

Why is Japanese Knotweed a Problem?

The problem with Japanese Knotweed is the rapid speed at which it can grow, the considerable damage it can cause and the difficulty in eradicating it once it is established. Just a small piece of a plant a couple of centimetres long can quickly grow into a large expanding plant. Drains, foundations, tarmac drives and even the walls and floors of houses can suffer structural damage from this fast growing plant. Proper treatment plans are required to deal with the plant which can take years to eradicate entirely from a site. The presence of Japanese Knotweed can therefore deter potential buyers or affect the price which they are willing to pay for a property.

What Should I Do If I Think I Have Japanese Knotweed in the Garden?

If you suspect that you may have Japanese Knotweed then you should consult a specialist contractor who is experienced and licensed to deal with the treatment of such plants and can identify whether the plant is present as other plants can be similar in appearance. If the contractor confirms the presence of Japanese Knotweed then they will be able to offer a programme of treatment which may depend on the size of the plant and its location. Proper treatment can take years to totally eradicate the plant and may not be cheap but simply cutting down the plant or treating it with normal weedkiller may make the problem worse. Even if only a small piece of root is left then the plant can grown again from this and it is an offence to remove soil with any Japanese Knotweed present as this will spread it to a new site.

How is Japanese Knotweed Treated?

Attempts to treat the plant with natural means, such as Aphids, have proved ineffective so most common treatments involve sprays and stem injections. A specialist contractor will need to monitor the site during and after treatment as it can take several years to eradicate the plant entirely.

Does the presence of Japanese Knotweed Need to Be Disclosed?

The Property Information Form which Sellers complete now includes a question about Japanese Knotweed to ensure that the Seller discloses this to any buyer if they are aware of it. However, buyers should look out for any plants which look like Japanese Knotweed and, if they have concerns, arrange for a specialist contractor to carry out an inspection.