What to do about Japanese knotweed from a neighbour

Spotting knotweed creeping under the fence from next door is frustrating. The good news is that the first steps cost nothing and are often all it takes. Most of this you can do yourself.

New to knotweed? Our Japanese knotweed overview covers the basics.

Start with the free options

Plenty of neighbours will be just as keen as you to get it sorted. If that’s how it goes, agree who’s doing what and keep the record going until it’s dealt with.

If you’re not sure it’s knotweed

Before you raise it, it helps to be fairly confident of what you’re looking at. Good photos and a look at reliable identification guidance are a sensible start. GOV.UK’s knotweed guidance links to a description and photos from the GB Non-native Species Secretariat, and the Royal Horticultural Society has a free page with photos of the plant at different stages of the year.

If you need certainty, a knotweed survey gives you a written report you can share.

Who’s responsible for knotweed on someone else’s land

This is where it gets more formal, and where the details matter. It isn’t against the law to have knotweed on your land. GOV.UK guidance for England says an owner doesn’t legally have to remove it unless it’s causing a nuisance, but they must stop it spreading off their property. Under the Wildlife and Countryside Act 1981 it’s also an offence in England and Wales to plant knotweed or otherwise cause it to grow in the wild, and Scotland has its own version of that offence. If it spreads onto your land, you may have a claim in private nuisance. That’s a civil claim for unreasonable interference with your use and enjoyment of your land. In Network Rail v Williams (2018), the Court of Appeal in England and Wales held a landowner liable where knotweed roots had spread from its land into neighbouring gardens, it knew or should have known about the risk, and it hadn’t taken reasonable steps to deal with it. The same court said a drop in your home’s value is not, on its own, enough for a claim. Councils and the police in England and Wales can use a community protection notice under the Anti-social Behaviour, Crime and Policing Act 2014. Home Office guidance says this can require someone to control knotweed where their failure to act is having a persistent, unreasonable and harmful effect on the quality of life of people nearby, and that in most cases it will be the council that uses it. A written warning must come first, and breaking a notice is a criminal offence. You can’t issue one yourself, but you can report the problem to your council and ask it to look into it.

Your paper trail matters most here. Clear notes and photos make any of these routes easier to follow, and they’re the first thing anyone advising you will ask for.

Reporting Japanese knotweed

If talking to the owner hasn’t worked, or you can’t find out who the owner is, you can report it. Who to report it to depends on whose land it’s on. Your photos and log do most of the work.

• The landowner or managing agent. For land owned by a business, a housing association or a landlord, a written report to whoever manages it is the first step. If you rent your own home, tell your landlord too.
• Your local council. A council can investigate and, if the informal route fails, may serve a community protection notice on whoever is responsible for the land (see above). Many councils say they don’t treat knotweed on land they don’t own. At many councils the environmental health team deals with complaints about knotweed on private land, and some have an online form for reporting it on council land such as parks.
• Rail land. If it’s growing from a railway embankment or other rail land. Network Rail asks lineside neighbours to raise knotweed enquiries through its national helpline on 03457 11 41 41 or the contact page on its website. Network Rail is under the same rules as any other landowner: in Network Rail v Williams (2018) the Court of Appeal held it liable in nuisance for knotweed that had spread from its land into neighbouring gardens.
• Roads and verges. If it’s on a roadside verge or highway land. In England, National Highways looks after motorways and major A roads. You can report a problem, including overgrown vegetation, through its online Report a problem service or on 0300 123 5000. Other roads are run by the local council. In Scotland, Transport Scotland takes reports about trunk roads on its Traffic Customer Care Line, 0800 028 1414, and local roads go to the council. In Wales, Traffic Wales takes reports about the motorways and trunk roads it manages, online or on 0300 123 1213 for urgent issues. We couldn’t find guidance written specifically for highway authorities. The general rule in GOV.UK guidance is that anyone with invasive non-native plants on their land must stop them spreading and causing a nuisance or damage to other land, or they could be responsible for the damage.
• Rivers and other public land. There’s no single body for this. The Environment Agency says it isn’t responsible for dealing with knotweed, although you can contact it for guidance. Responsibility sits with whoever owns the land. If that’s the council, for example a park or a riverbank it owns, many councils let you report it online.

When you report it, include where it is (a postcode and a short description of the spot), dated photos and a short note of what you’ve already tried. Keep a copy of what you sent and any reference number you get back. Reports have a way of disappearing into a queue, so a reference makes the follow-up email much easier.

When to take action beyond a conversation

Sometimes the friendly route stalls. The neighbour doesn’t reply, says they’ll deal with it and doesn’t, or disagrees that it’s knotweed at all.

That’s the point to think about getting help. A specialist can survey the plant on your side, set out how far it has spread and write it down. That report is useful in any later conversation, with your neighbour or anyone else. If talking, writing and mediation haven’t worked and you’re thinking about a claim, that’s the time to take legal advice. GOV.UK describes going to court as a last resort because of the cost, and says you can get free legal advice from a law centre, an advice centre or Citizens Advice.

When a specialist helps

You can handle the conversation, the letter and the records on your own. A specialist is worth it when you need a firm answer on what the plant is, how far it has spread or what it will take to deal with. Ask for their findings in writing, separate from any quote for treatment.

If you’re thinking of selling, it’s worth getting this in order early. Our guide to selling a home with Japanese knotweed explains why.