Japanese Knotweed Fallopia japonica is perennial and spreads through underground stems (rhizomes) and can regrow from small fragments even though it does not set seed. It is very invasive. Digging out is possible, but as rhizomes grow deeply, regrowth usually occurs which needs destroying. This method also creates problems over disposal as Japanese knotweed is classed as ‘controlled waste’ under the Environmental Protection Act 1990. This requires disposal at licensed landfill sites. Alternatively, it can be destroyed on site by cutting or digging it repeatedly and burning it when dry. In this way the energy reserves in the remaining underground parts will be gradually exhausted; a process which may, however, take several seasons. Similarly treatment with herbicides will require several repeated applications. On no account should Japanese knotweed be included with normal household waste or put out in green waste collection schemes.