Herbicide applications alone can effectively work so the plant is unable to produce new growth (this is viewed as successful treatment) but are unlikely to remove 100% of the underground rhizome system. During and following treatment, the ground will still contain herbicide treated rhizome.
Under the Environmental Act 1990, Japanese Knotweed and material (soil) contaminated by Japanese Knotweed is classed as controlled waste (according to the Environmental Protection Act (Duty of Care) Regulations 1991), therefore it must be disposed of safely at a licensed landfill site.
Given the above, the ground should remain undisturbed within 7m of the Japanese Knotweed after successful treatment and during the Guarantee period to ensure that the Guarantee is not rendered null and void.
During this time, should you wish to make any changes to your garden, we advise they should only be aesthetical e.g. potted plants or laying gravel. You must not disturb or plant directly into the contaminated soil. If, during the Guarantee period, landscaping or development works are planned within 7m of the treatment area, then all works must be supervised by the Japanese Knotweed Specialists to ensure the terms of the Guarantee are observed.