The land-owner is legally obliged to ensure that Japanese Knotweed does not spread from outside their boundaries, and by allowing this, they are subjecting themselves to prosecution, alongside a £2,500.00 fine. Although it is illegal to allow the Knotweed to spread, it is not illegal to have it on your land, and unless your neighbour has let it get onto your land, you are unfortunately unable to take them to court.

If the Japanese Knotweed is, however, within 7 metres of your boundary, you can take them to court for the devaluation of your property. In some severe cases, devaluation can occur for up to 50% of the estimated value of the property! This is a great risk, especially if you are wanting to sell your property in the future. We would then recommend that you proceed with a site survey report and management plan, this will give you a firm basis to argue to the courts why the neighbour is liable for the treatments of the Knotweed.