Japanese Knotweed In A Neighbour's Garden

What's happening?

GOV.UK's guidance for England says you must stop Japanese knotweed on your land from spreading off your property, that you do not legally have to remove it unless it is causing a nuisance, and that you can be prosecuted for causing it to spread into the wild. The RHS adds that it is an offence under the Wildlife and Countryside Act 1981 to plant or cause it to grow in the wild, and that knotweed material is controlled waste under the Environmental Protection Act 1990. The RICS professional standard says courts have confirmed that knotweed is an actionable nuisance and that neighbouring owners have been required to control it to stop spread onto neighbours' land, citing a 2018 Court of Appeal case in England. A legal claim is for a solicitor.

What usually causes it?

• Knotweed established in the neighbour's garden or on land they own, spreading by rhizomes under the boundary
• A neighbour who has not noticed it or has not treated it
• Digging, strimming or cutting by the neighbour, which spreads fragments
• Soil or plant material moved from an infested site
• A plant that has been mistaken for something else, so check identification before accusing anyone

Is it dangerous?

Not to health. The risk is damage and spread: the RHS says knotweed regenerates from small fragments and forms dense thickets, and GOV.UK says contaminated soil and plant material may be controlled waste. A neighbour who allows it to spread may face prosecution, and you could face the same if you spread it yourself.

Can I fix it myself?

Check it is knotweed: the RHS page has identification help. Photograph it and note where it is and where it comes over your boundary. Talk to your neighbour, bring the photographs and ask them to arrange treatment. Keep copies of what you send. Do not cut, dig, strim or move it yourself, and do not put any in a household bin or green waste: the RHS says it is controlled waste, and GOV.UK describes how treatment and disposal must be done. If your neighbour will not act, you can ask your council about its powers, and take advice from a solicitor about a civil claim for nuisance. This page describes England; GOV.UK links to guidance for Scotland, Wales and Northern Ireland.

When should you call a gardener?

Use a specialist knotweed contractor for treatment and disposal, because the waste has to be handled as controlled waste. A gardener can help with identification and with your own beds once a specialist plan is in place, but should not dig or strim a knotweed stand.

What will the gardener actually do?

• Confirm the plant is Japanese knotweed and map the extent on both sides of the boundary
• Prepare a treatment and management plan, including an insurance-backed guarantee where one is wanted
• Treat with approved herbicides as GOV.UK describes, with the permissions it lists
• Dispose of the waste at a permitted facility with the right paperwork
• Monitor for regrowth after treatment

Questions people ask

Sources & References

1. GOV.UK: how to stop Japanese knotweed from spreading
2. RHS: Japanese knotweed
3. RICS: Japanese knotweed and residential property