Like Balsam, knotweed is classified as "controlled waste" under the Environmental Protection Act 1990, meaning that any part of the plant and related material must not be removed from its original location except to be disposed of at a licensed waste facility. Many populations will have been treated with chemicals for removal and so harvesting this plant for consumption can also be problematic. Knotweed is delicious however and there are examples of it being carefully foraged and used on menus around the country. We certainly won’t be telling the Department for Environment Food and Rural Affairs.