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What you can do to help prevent the spread of invasive plants

There are several steps you can take to stop the spread of invasive plants:

• know what you are growing - take care when swapping plants
• dispose of all plant waste responsibly
• know what you are buying - avoid buying plants or seeds known to be invasive

For more information on how to help prevent the spread of invasive non-native plants
follow the link below.

• The Horticultural Code of Practice: Help to prevent the spread of invasive non-native plants leaflet (PDF document 1.87M) Opens new window
• Help with PDF files

Identifying common invasive non-native plants

Three of the most invasive non-native plants are Japanese Knotweed, Giant Hogweed and Himalayan Balsam.

Japanese Knotweed
Japanese Knotweed appears to have no natural enemies in Britain and is difficult to control, tiny fragments (as little as 0.7g of its rhizome, or root) can produce a viable plant. This plant can grow as much as two centimetres per day, will grow in any type of soil, no matter how poor, and can grow through walls and concrete.

The plant forms dense clumps up to three metres in height. It has large, triangular green leaves and a hollow stem, similar to bamboo but often flecked with dark red. Japanese Knotweed produces fleshy red-tinged shoots that can reach a height of 1.5 metres by May and 3 metres by June.

You can find out more about this plant and how to control and dispose of it from the Environment Agency, the Devon Knotweed Forum and Natural England (tel 0117 959 8622).

• Download Environment Agency advice on management and disposal of Japanese Knotweed Opens new window
• Download advice from the Devon Knotweed Forum on management and disposal of Japanese Knotweed Opens new window

Giant Hogweed
Giant Hogweed has a green stem with dark red or purple blotches and spiky dark green leaves. The plant can grow up to 5m tall and grows mainly in areas of damp soils, such as river banks.

Each flowerhead can produce up to 50,000 seeds, which are easily dispersed by water. Seeds can remain viable for up to 15 years so disposal has to be carried out very carefully.

Giant Hogweed can have adverse effects on skin following contact. Symptoms are usually noticeable within 24 hours including blisters and swelling on the skin, which may be made worse by exposure to the sun. If you feel unwell after contact with Giant Hogweed speak to your doctor.

Japanese Knotweed and Giant Hogweed are listed in the Wildlife and Countryside Act 1981. This means that it is illegal to plant it in the wild. Waste from some non-native plants is controlled by law and so certain regulations have to be complied with when disposing of such material.

• Further advice on how to identify, control and dispose of invasive plants is available from the Environment Agency Opens new window

Himalayan Balsam
Himalayan Balsam was introduced into Britain in the 19th century. It has pinky red stems with dark green leaves. It grows fast and can reach 2 to 3m in height. The plant can produce large quantities of seed in exploding capsules that can throw seed several metres.

Controlling harmful weeds

Five particular plants are classified as 'injurious', or harmful weeds under the Weeds Act 1959. These five plants are:

• Common Ragwort
• Spear Thistle
• Creeping or Field Thistle
• Curled Dock
• Broad-Leaved Dock

Ragwort is harmful to, and can kill, horses and livestock. All parts of the plant are poisonous.

Contact the National Association of Agricultural Contractors for a list of approved contractors to control harmful weeds - or call 01733 362 920.

• National Association of Agricultural Contractors Opens new window
• More information on controlling the spread of harmful weeds from Natural England Opens new window
• Guidance on the disposal options for Common Ragwort Opens new window

Legal status of harmful weeds

It is not an offence to have these weeds growing on your land. However, they must not be allowed to spread to agricultural land, particularly grazing areas or land used to produce animal feed. Natural England may issue enforcement notices to prevent the spread of harmful weeds to agricultural land.

If you suspect harmful weeds are on land near you there are several organisations you can contact:

• the Wildlife Licensing Unit of Natural England for privately owned land
• the Highways Agency for verges of large main roads (trunk roads) or motorways
• your local council for all other roadside grass verges or council owned land
• Network Rail for railway land or embankments
  

• Contact the Highways Agency about weeds Opens new window
• Network Rail injurious weed information Opens new window
• Search for your local council in England Opens new window

More useful links

• Weed control advice from the Royal Horticultural Society Opens new window