Invasive plants

Plants that have been introduced to a place where they do not naturally occur are known as non-native species. Many of these live happily in the UK without causing a problem, but a few become what's called invasive; a foreign invader.

Invasive species upset the balance of the ecosystem as they may be bigger, faster growing or more aggressive than the native species. They may also have fewer natural predators to control numbers. The native species are often unable to compete and fairly quickly the invasive species take over and can displace native plants, reduce wildlife interests and could cause damage to roads, footpaths and structures, such as building foundations.

Helping to prevent the spread of invasive non-native species

• Horticultural code of practice leaflet (PDF)
• Handling and working with invasive plants
• Prevent the spread of harmful invasive and non-native plants

Treat/dispose invasive non-native plants

• Treat invasive non-native plants

Japanese knotweed

Japanese knotweed grows pretty much anywhere and can block footpaths, damage concrete, tarmac, flood defences and the stability of river banks.

Japanese knotweed is probably the most invasive plant in Britain and is scheduled under the 1981 Wildlife and Countryside Act, so that it is an offence to plant or cause it to grow in the wild. In addition under the Environment Protection Act (1990) Japanese knotweed is classified as ‘controlled waste’ and must be disposed of at a licensed landfill site in accordance with the Environment Protection Act (Duty of Care) Regulations 1991. If it spreads onto a neighbour's land, you could be taken to court.

More details on knotweed and its code of practice can be found on the Environment Agency website.

Whose responsibility?

Managing Japanese knotweed is the responsibility of the owner/occupier of the site. While there is no statutory requirement to control/eradicate this invasive, nor is it necessary to report its presence (it is not listed in the Weeds Act 1959), it is prudent to take action to control its spread quickly.

Giant hogweed

Giant hogweed is a species with both occupational health and environmental problems. When giant hogweed sap comes into contact with skin, it reacts with sunlight and causes chemical skin burns. Giant hogweed sap becomes more toxic as the year progresses and the plant is exposed to more sunlight.

Himalayan balsam

Himalayan balsam or Indian balsam grows in dense stands that suppress the growth of native grasses and other plants.