Japanese Knotweed: Who Is Responsible?

Why Japanese Knotweed Causes So Many Problems

Japanese knotweed can make a property extremely difficult to sell. Many mortgage lenders are cautious about properties with an active infestation, and while policies vary between lenders, most will want to see a management plan and proof of treatment before proceeding with an application.

This makes knotweed spreading from a neighbouring property a serious concern. What might look like just another weed can affect your home's value, your ability to remortgage, and your chances of selling in future.

The plant spreads aggressively through its root system, which can extend several metres from the visible stems. It can push through tarmac, damage drainage systems, and exploit any weakness in built structures. A small patch in a neighbour's garden can become your problem within a growing season or two.

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Is Your Neighbour Legally Required to Remove It?

There is no law in England and Wales that forces a homeowner to remove Japanese knotweed from their own land. Many people assume otherwise, but simply having knotweed in your garden is not itself illegal.

What is illegal under the Wildlife and Countryside Act 1981 is causing knotweed to spread into the wild. This applies to disposing of contaminated soil or plant material incorrectly, which must be taken to a licensed landfill site.

The more relevant issue for neighbours is private nuisance. Under common law, if knotweed spreads from your neighbour's property onto yours, you may have grounds to take legal action against them. The spread itself can be treated as a nuisance, regardless of how the knotweed got onto your neighbour's land in the first place.

The Court of Appeal confirmed this principle in Network Rail Infrastructure Ltd v Williams in 2018. The ruling established that allowing knotweed to encroach onto neighbouring land is actionable as a nuisance, even if the landowner did not plant it themselves. The duty is to take reasonable steps to prevent spread once you know or ought to know the plant is there.

Your situation may be slightly different. ask a question below ↓ and our editorial team will reply with our advice.

What Can You Actually Do?

Start by speaking to your neighbour directly. Many people do not realise they have knotweed or understand how quickly it spreads. A straightforward conversation sometimes prompts them to arrange treatment, though results will depend on the neighbour. Removal costs vary significantly based on the extent of the infestation and treatment method, so obtaining quotes from multiple specialist contractors is advisable.

If your neighbour refuses to act or cannot be contacted, you have a few options:

• Write a formal letter explaining the problem and asking them to arrange treatment within a reasonable timeframe. Keep a copy.
• Consider mediation as an alternative to immediate legal action. This can be quicker and less costly than court proceedings.
• Instruct a solicitor to send a letter before action. This sets out your intention to pursue a civil claim if the problem is not addressed.
• As a last resort, you can bring a claim in nuisance through the county court. You may be able to recover the cost of treating knotweed on your land and any reduction in property value.

Keep records of the infestation, including dated photographs showing the spread over time. Maintain a log of all communications with your neighbour about the issue. If you commission a professional survey, retain the report. This evidence will be useful if the matter escalates.

Getting Professional Help

Treatment should be carried out by a specialist contractor with experience in knotweed removal. The Property Care Association maintains a list of qualified professionals who can provide insurance-backed guarantees, which many mortgage lenders now expect to see.

You can treat knotweed on your own land without waiting for your neighbour to act on theirs. However, for any long-term solution to work, the source next door will eventually need treating too, otherwise the plant will continue to spread back across the boundary. Coordinating treatment with your neighbour, where possible, produces far better results.

Knotweed waste must be disposed of through licensed facilities to comply with legal requirements. For detailed guidance on disposal and your responsibilities as a landowner, consult the information available on GOV.UK. If you are unsure of your legal position before taking action against a neighbour, seek advice from a solicitor familiar with property disputes.

The Next Step

Now that you have read through the advice above, you might want to put it into practice. Our Neighbour Rights Checker lets you check your legal rights in any neighbour dispute. Takes 1 minute. Try it now →