Japanese Knotweed

Japanese Knotweed Japanese Knotweed is a strong-growing, clump-forming perennial, with tall, dense annual stems. Stem growth is renewed each year by deeply-penetrating rhizomes (creeping underground stems).

It is classed as an invasive species of plant, and is considered a particular problem as it can block footpaths and damage concrete, tarmac, flood defences and the stability of river banks.

Japanese Knotweed is spread when small pieces of the plant or rhizomes are broken off. One piece of rhizome or plant the size of a fingernail can produce a new plant.

Legal implications

  • it is not illegal to have Japanese Knotweed on your land
  • you must not allow Japanese Knotweed to spread onto adjacent land the owner of that land could take legal action against you
  • plant or encourage the spread of Japanese Knotweed outside of your property - this can include moving contaminated soil from one place to another or incorrectly handling and transporting contaminated material.
  • the Anti-social behaviour, Crime and Policing Act has been reformed so that community protection notices may be used to prevent growth of Japanese knotweed.

What should you do?

Digging out is possible, but due to the depth that the rhizomes can penetrate, regrowth usually occurs.  This method also creates problems over disposal as Japanese knotweed is classed as a 'controlled waste' under the Environmental Protection Act 1990. This requires disposal at licensed landfill sites.

Contractors

Specialist Japanese knotweed contractors are usually licensed to safely remove the weed from site but check first before employing their services. You can find contractors on the web but we recommend you get three quotes for any works.

Alternatively, it can be destroyed on site by allowing it to dry out before burning. On no account should Japanese knotweed be included with normal household waste or put out in green waste collection schemes.

Weed killer

The most effective and simplest method for the home gardener to tackle Japanese knotweed is with the glyphosate-based weed killer. This is often sold as Roundup, or ask your supplier for a suitable weed killer.  Glyphosate is usually applied to the foliage and is passed within the plant to the underground parts.

How the new powers can be used to tackle Japanese Knotweed?

The Anti-social Behaviour, Crime and Policing Act 2014 does not explicitly refer to Japanese knotweed or other, similar invasive non-native plants, as the new anti-social behaviour powers are intended to be flexible.

Community protection notices can be used to require someone to control or prevent the growth of plants like Japanese knotweed which are capable of causing serious problems to communities.  The test is that the conduct of an individual or body is having a detrimental effect of a persistent or continuing nature on the quality of life of those in the locality, and that the conduct is unreasonable (includes "a failure to act").

Local councils can issue notices for invasive non-native species like Japanese knotweed. The notice can require the person responsible for the land in which the knotweed is growing to take steps to rectify the problem.

Further information on 'Anti-social Behaviour, Crime and Policing Act 2014 and news article on anti-social behaviour powers of knotweed

Further general advice

Anti Social Behaviour Powers Knotweed

RHS advice