Under UK law relating to Japanese Knotweed, homeowners don’t have to take any action if they so wish, but they do have a legal responsibility to make sure that Japanese knotweed does not spread from their land onto adjoining neighbouring land. There is no legal obligation for any homeowner or landowner to inform anyone that knotweed is present on their land, they are also not legally obligated to remove or even treat it. It is legal for adjoining land to have Japanese Knotweed present on their land; however, they would be breaking the law if they allow it to spread.