Japanese Knotweed material is regarded as ?controlled waste? and not disposing of it properly would be an offence under the Environmental Protection Act, 1990. Allowing the spread of Japanese Knotweed into the wild is also an offence under the Wildlife and Countryside Act 1981. This is the best website I've found about knotweed: http://www.devon.gov.uk/index/environmentplanning/natural_environment/biodiversity/japanese_knotweed.htm This is quite good: http://www.environment-agency.gov.uk/homeandleisure/wildlife/130079.aspx