Japanese knotweed

Japanese Knotweed is an invasive non-native plant (INNP). It has become a serious problem in some areas of the UK.

It can -

  • spread quickly
  • takes over other plants
  • cause damage to property.

It commonly spreads quickly by -

  • rhizomes - roots
  • crown - base of the stem
  • stem segments

if damaged or disturbed for example during -

  • garden clearance
  • construction work
  • garden waste.

The Non-native Species Secretariat website helps you to understand if you have found Japanese Knotweed. It also includes information on other forms of non-native invasive species.

It causes problems because it -

  • can force its way through concrete or brick, so can damage buildings or roads
  • grows in thick clusters, which means native plants can’t grow
  • is very difficult to get rid of
  • can result in a reduction in land values and affect the ability to get a mortgage

On your property

If you find Japanese Knotweed growing on your land, treat the plant as early as possible. This is to stop it from spreading and becoming a problem.

Tell your neighbours if you believe you have Japanese Knotweed on your land. They can then see whether it is present in their gardens.

Early identification and treatment will stop the plants from further spreading.

It usually takes at least 3 to 4 seasons to remove Japanese Knotweed using the appropriate weed killer. If using chemical treatments ensure these are used safely. Follow manufacturer's instructions and wear appropriate PPE at all times.

If you are considering using any form of chemical agent and your land is next to or near any watercourse, contact the Environment Agency prior to any treatment. You can do this by calling 03708 506 506. Avoid damage to non-target plants by spraying during still dry conditions without rain for 6 hours.

If you intend to spray any chemicals on any land which is not your own, you will likely need to be an approved contractor. The contractor must have a National Proficiency Tests Council Certificate of Competence if spraying not on your own land.

If you find this is ineffective, we recommend you contact professional contractors who have access to more powerful chemicals. This may reduce this period by half.

When dealing with Japanese Knotweed on your property, you must not -

  • dispose of any part of the plant in your brown wheelie bin, black wheelie bin or compost bin
  • spread soil contaminated with Japanese Knotweed as this could affect a greater area
  • take it to your local household waste and recycling site
  • dump or fly-tip cuttings

You must stop Japanese Knotweed spreading from your land. You could face legal action and costs if you allow it to spread onto someone else’s property.

On your neighbour’s property

Speak to your neighbour if you are concerned that Japanese Knotweed may be on their land. Make them aware what you have found as they might not realise that there's an issue.

If your neighbouring property is owned by us, contact us by calling 01482 300 300. Request to speak to our Housing or Property Team.

If this doesn’t work, we recommend you contact the Citizens Advice Bureau. You can also seek independent legal advice.

Speak to your home insurance company for help and advice if you feel your property is damaged. 

Further information can be found here.

On land around a railway

If you find Japanese Knotweed next to a railway line, embankment or station, contact Network Rail. Ask them to treat the problem and confirm.

In a park, public land, open space or other council land

To report Japanese Knotweed in any -

  • park
  • public land
  • open space
  • other form of council land

Contact us by telephone - 01482 300 300.

Giant hogweed

Giant hogweed is an invasive non-native plant (INNP). Advice should be followed, as above, about its removal and treatment.

You should follow the same advice on the removal of Japanese Knotweed. This will vary on whether this is on private land, council land, public open spaces or railway land.

Sap from this plant contains a chemical. In the presence of sunlight, it can cause a potentially dangerous skin reaction with those who come into contact with it. Symptoms may include -

  • burning
  • itching
  • blistering

Blistering can take 24 to 48 hours to appear after exposure. Dense pigmentation is visible after three to five days. Lesions caused from contact may be slow to heal. They could result in consequent scarring, which may persist for many years. Any reaction to giant hogweed can be especially acute in children.

If persons have come into contact with giant hogweed, they should cover the affected area of skin immediately from sunlight. They need to wash the affected skin with cold water as soon as possible. If contact is with the eyes or blisters occur, seek medical advice immediately.

For further advice about Giant Hogweed, visit the Royal Horticultural Society (RHS) Gardening Giant hogweed advice page.