Japanese knotweed Reynoutria japonica

Photo: GBNNSS

• Appearance: Tall, perennial terrestrial plant with stems, typically 2 m in height, with extensive system of underground rhizomes. Hollow, green-flecked stems, leaves grow alternate in a zig-zag pattern.  White flowers. 

• Growth: Fast-growing, forms dense stands. Thrives in damp soil particularly in urban places. Spread through small fragments of stem or rhizome.

• Impact: Displaces native species, can contribute to erosion and flooding. Can have significant economic impacts and may be difficult and expensive to control.

• Pathway: Originally a garden ornamental plant that has spread, been deliberately planted or escaped into the wild.

• Legal status: Listed on Schedule 9 of the Wildlife and Countryside Act 1981. Section 14 of this Act makes it an offence to plant or otherwise cause to grow in the wild.  

• If an offence has been committed: Make a report to your local Police force.

• If Japanese knotweed is causing a nuisance: It is not an offence to have Japanese knotweed growing on your land but there may be a civil liability if it is allowed to encroach onto others’ land. Contact a solicitor for more information.  

• In some cases, a Community Protection Notice under theAnti-Social Behaviour, Crime and Policing Act 2014 could be issued by your local authority or local Police to individuals who “are acting unreasonably and who persistently or continually act in a way that has a detrimental effect on the quality of life of those in the locality”.  This could be in relation to Japanese knotweed.  Contact your local Police force or local authority to find out more.

• What to do if you see this plant in the wild: Record it with a photograph (where possible).

• Make sure you don’t spread this plant: Do NOT strim, flail, mow or dump plant material or contaminated soil. Check Clean Dry boots and equipment and Be Plant Wise in your garden.

• Links to more: Species information and ID sheet.