Japanese Knotweed And The Law: What Property Owners Need To Know

Introduced to the UK in 1850, Japanese knotweed was once admired as an ornamental garden plant. 175 years later, it has become one of the UK's most invasive and problematic species, and not just for the environment. For property owners, buyers and developers, its presence can cause serious legal and financial complications.

We know that discovering Japanese knotweed can feel overwhelming and frustrating, especially when you are worried about your home, a sale falling through or unexpected costs. You deserve clarity and the right support from the outset, and we are here to help you understand your options.

In this article, Francesca Harris, Solicitor in our Litigation and Dispute Resolution Department, explains what Japanese knotweed is, why it matters in property law within England and Wales, and what steps landowners, sellers and buyers should take to protect themselves.

What is Japanese knotweed and why is it a problem?

Japanese knotweed (Fallopia japonica) is a fast-growing, bamboo-like plant with deep roots that can extend several metres underground.

As an invasive species, its ability to spread aggressively means it can cause significant structural damage to:

• Buildings and foundations
• Roads and drainage systems
• Retaining walls and hard surfaces

Even where no physical damage has occurred, the plant's presence alone can complicate property transactions and expose owners to legal claims.

What does the law say about Japanese knotweed in the UK?

This plant creates various complications for property owners and developers for several reasons, and it is crucial to understand its role in a sale, purchase or development before proceeding.

1. Owning it is not illegal, but letting it spread is

Under the Wildlife and Countryside Act 1981, Japanese knotweed is a controlled plant. Having it on your land does not mean you are breaking the law, but allowing it to spread into the wild or onto another property is an offence.

When disposing of knotweed, you must follow the Environmental Protection Act 1990, as it is classed as controlled waste. It must be taken to a licensed disposal site; you cannot simply place it in a skip or compost heap.

Allowing knotweed to spread can lead to costly legal claims.

2. You could be served with a Community Protection Notice (CPN)

Local Councils have powers under the Anti-Social Behaviour, Crime and Policing Act 2014 to issue a Community Protection Notice if you fail to manage knotweed and it affects neighbouring properties or the wider community.

3. Knotweed can amount to a private nuisance

In the landmark case of Williams v Network Rail Infrastructure Ltd [2018] EWCA Civ 1514, the Court of Appeal found Network Rail liable for creating a nuisance by allowing knotweed to spread onto neighbouring land.

The Court held that even though there was no physical damage, their failure to control the knotweed interfered with neighbours' use and enjoyment of their property.

Subsequent cases have clarified that liability may arise even without encroachment if the landowner fails to take reasonable steps to control the spread, or misleads buyers by not disclosing knotweed during a property transaction.

Even if you have done nothing wrong, the presence of Japanese knotweed can lead to challenging conversations with neighbours, buyers or lenders. Our role is to protect you, minimise the impact and keep matters moving forward.

What legal claims can be made if Japanese knotweed spreads?

Allowing knotweed to spread can expose you to several legal claims, including:

• The cost of knotweed treatment and removal
• Loss of property value, also known as diminution in value
• Legal expenses
• Compensation for inconvenience or stress
• Claims for private nuisance
• Misrepresentation after a property sale

Should you find yourself facing legal claims, or you have discovered knotweed on your property, we are here to help. We can:

• Review your legal responsibilities and rights as a property owner
• Advise you on disclosure obligations when selling the property
• Support you during disputes or misrepresentation claims
• Work alongside surveyors and treatment specialists
• Help you communicate and negotiate with neighbours or buyers
• Take swift legal action if a third party has caused knotweed to impact your property

Our priority is to protect your property, your financial position and your peace of mind.

Do you have to disclose Japanese knotweed when selling a property?

When selling a residential property, you are required to complete a TA6 Property Information Form. Question 7.8 of the form asks whether the property is affected by Japanese knotweed.

Answering this question dishonestly or carelessly, even if you are unaware of an infestation, could lead to a misrepresentation claim after the sale. Courts have found sellers liable for answering "No" when knotweed was later discovered, especially where a reasonable inspection would have revealed it.

How property buyers should investigate Japanese knotweed

If you are buying land or property, particularly in high-risk areas, consider taking the following precautions:

• Commission a professional knotweed survey.
• Request evidence of any past treatments and warranties.
• Check with your mortgage lender; some banks may refuse to lend on properties affected by knotweed.
• For developers, early identification and treatment can prevent costly delays to projects.

Practical tips for property owners

If you discover Japanese knotweed on your land:

• Act quickly – ignoring it will only make the problem worse.
• Seek professional help – use a qualified specialist with an insurance-backed treatment plan.
• Keep detailed records – maintain evidence of your actions to show you are managing the issue responsibly.
• Communicate with neighbours – joint action can prevent disputes and strengthen your position.

Key takeaways for property owners

• Japanese knotweed is not illegal to own, but allowing it to spread is a criminal offence.
• Its presence alone can impact property values, lending decisions and the ability to sell.
• Landowners may face nuisance and misrepresentation claims if you do not act responsibly.
• Sellers must accurately disclose knotweed using the TA6 Property Information Form.
• Buyers should carry out inspections and request treatment records before committing to a purchase.
• Prompt action and professional advice are essential to reduce both legal and financial risk.

Japanese knotweed is more than just a gardening nuisance; it can feel like a threat to your home, your sale or your investment. You do not need to manage that stress alone.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.