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Japanese knotweed

What should you do if a survey mentions Japanese knotweed?

Japanese knotweed matters because it spreads, not because a garden clump is automatically a crime. In England you need not remove it unless it is a nuisance, but you must stop it leaving your land. Causing it to spread into the wild can be prosecuted. A survey note asks for identification, not a species certificate.

Last reviewed 24 October 2026. Written for buyers in England and Wales unless a source says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.

Is it illegal to have Japanese knotweed?

In England, no, not merely by having it. GOV.UK’s guidance, updated 12 February 2026, says you do not legally have to remove Japanese knotweed from your land unless it is causing a nuisance, but you can be prosecuted for causing it to spread into the wild. You must stop plants on your land spreading off your property. The same guidance says not to treat it yourself unless you have the appropriate skills and experience, and it sets strict rules for burial, burning and taking waste away. Soil that contains it is controlled waste. You must not sell that soil as topsoil or mix it into ordinary spoil.

Causing it to grow in the wild is the offence people half-remember. Dumping cuttings over the fence, fly-tipping crowns, or letting a contractor take it away as ordinary green waste are the ways buyers get into trouble. A managed stand, treated by someone who knows what they are doing, is a different set of facts from a pile of canes in a neighbour’s skip. This page is about England’s published guidance. Scotland, Wales and Northern Ireland have their own rules. Do not assume the sentence travels unchanged.

What does a surveyor’s knotweed sentence actually mean?

RICS members who survey homes use the professional standard Japanese knotweed and residential property, 1st edition, effective 23 March 2022. It is there to help them make a preliminary assessment, not to turn them into botanists. If the report says the plant has the appearance of Japanese knotweed, or that it could not be confirmed out of season, believe the limit. Dead winter canes and bindweed get misnamed both ways. The next step is a specialist who will identify it, not a price reduction invented from a hedge.

The 2022 standard replaced a crude distance rule. Writing in the RICS Property Journal on 21 March 2022, the standard’s author described four management categories. Category A, Action: knotweed is causing visible material damage to a significant structure. Category B, Action: no such damage, but knotweed is likely to prevent use of amenity space. Category D, Report: knotweed on neighbouring land, with the relevant distance reduced to three metres, where a lender retention was not expected because the owner cannot control that land. Lenders do not have to follow RICS’s expectation. Ask your lender what they will require. Do not rely on a blog that still quotes a seven-metre mortgage ban as if it were the current RICS method.

Will a lender refuse the mortgage?

Some will want a management plan from a specialist, some will want a retention until treatment starts, and some will lend with the category on file. RICS’s journal said most lenders were expected to look for a specialist report where the assessment is Action, category A or B, and were not expected to retain money for the neighbouring-land report category. “Expected” is not “your lender will”. The only reliable version is the condition in your mortgage offer.

On price, pay for identification and a management plan before you invent a figure. Treatment is often a programme over more than one growing season, not a single visit. Costs vary with the area of the plant, access, and whether waste must leave the site. We are not publishing a typical fee here because no official tariff exists that we can cite. Get two written plans. Then decide whether the seller reduces the price, starts the plan, or you walk away. A plant the surveyor could not confirm is not yet any of those things.

What should you not do with the canes?

Do not strim it, compost fresh growth, or put it in the council green bin. GOV.UK allows composting of dead brown canes on site only if they are cut, not pulled, at least 10cm above the crown. Fresh material is a different problem.
Do not bury it because a forum said two metres is fine. GOV.UK requires burial on the site it came from, at specified depths, with Environment Agency notification, and membranes that meet the rules if you use them.
Do not hire a person who will not say where the waste is going. You must use a registered carrier and a site permitted to take it, and tell the Environment Agency where it went.
Do not rely on the survey as an identification. Commission someone who will put the species in writing.

Common questions

What if the knotweed is in the neighbour’s garden?

You still care, because it can cross the boundary, but you do not control their land. RICS’s 2022 approach put nearby neighbouring growth in a report category rather than treating a wide radius as automatic damage. Your lender may still ask questions. Your solicitor can enquire. You cannot lawfully march next door and spray. GOV.UK’s duty not to cause spread runs both ways.

Can a survey miss it in winter?

Yes. The plant dies back. A visual inspection out of season can miss crowns, and a careful surveyor will say so rather than certify the garden clear. “No knotweed seen” in January is not a guarantee. If the seller’s form says it was treated, ask for the plan regardless of the season.

Where does the seller have to declare it?

On the property information form your solicitor receives, where the question is asked, and in answer to enquiries. The form’s wording changes over editions. Your solicitor knows which questions were put. A survey note and a seller answer that contradict each other are exactly what enquiries are for. Do not resolve the contradiction yourself in a text to the agent.

Does the seven-metre rule still decide mortgages?

Not as a RICS method. The 2022 professional standard moved off that crude distance. The Property Journal summary describes three metres for the neighbouring-land report category. Individual lenders can still ask for whatever their credit policy says, including a distance. Ask the lender. Do not pay for a strip of land to be excavated because a 2012 blog said seven metres.

Does knotweed always damage foundations?

No. RICS created a category for visible material damage to a significant structure precisely because that is a different case from a clump in the lawn. The dramatic claim that it always destroys houses is not the professional standard. Damage that is actually there is category A, and it needs a proper repair as well as a plant plan. Absence of damage does not mean you can ignore spread onto a neighbour.

Who should identify it?

Someone who will put their name to the species and a management plan, and who is not the cheapest person with a van. GOV.UK says not to treat it yourself without the skills. A surveyor’s “consistent with” is the reason you book that person. It is not itself the identification.

How much does treatment cost?

There is no official price we can cite. Herbicide programmes, excavation and supervised disposal are different jobs, and disposal of contaminated soil dominates the excavation figure. Treat any number on a forum as indicative gossip. Two written plans, reviewed against your site, are the price. Label anything else as not a quote.

The lender has declined. Is that the end?

It is the end of that offer, not a statement about every lender. Some will proceed with a specialist plan in place. A broker can ask. You can also decide the plant plus the lending friction is a reason to withdraw. Get the decline in writing so you know whether it was knotweed, valuation, or something else.

The seller says it was removed years ago. Is that enough?

Only with the paperwork: who did it, where the waste went, how many seasons of follow-up were completed, and whether any guarantee transfers. Rhizome can persist. GOV.UK’s disposal rules exist because fragments regrow. A sentence in an email from the agent is not a completion certificate.

Can you just buy and deal with it later?

You can if you have identified it, told the lender, and budgeted for a plan you are allowed to carry out. You should not if you have not told the lender something their form asks about. Spreading it later, including by DIY clearance, is the prosecution risk GOV.UK describes. Later is fine. Casual is not.

Sources

Key facts

England, legal: GOV.UK, updated 12 February 2026: you do not legally have to remove it unless it is causing a nuisance. You can be prosecuted for causing it to spread into the wild. You must stop it spreading off your property.
Disposal: GOV.UK: do not put it in ordinary green waste. Off-site disposal needs a registered waste carrier and a site permitted to take it. Burial on site has depth and notification rules, including telling the Environment Agency.
DIY: GOV.UK: do not treat it yourself unless you have the skills and experience.
RICS categories: The 2022 RICS professional standard uses management categories. The RICS Property Journal (21 March 2022) describes A and B as Action, and says the old seven-metre distance was replaced by a three-metre neighbouring-land category D that is Report, not an expected lender retention. Lenders still set their own rules.
Survey limit: A Home Survey is not a botanical identification. Winter die-back is easy to miss. “Appearance of” means what it says.