Japanese Knotweed has become something of a legend in UK property; part horticulture, part horror story. Its roots can disrupt paving and outbuildings, but the real power of knotweed is the fear it strikes in buyers, lenders and valuers.
And with recent changes to the TA6 Property Information Form and updated RICS guidance, this is one red flag every property professional needs to understand clearly.
Let’s get you up to speed in five minutes.
Why knotweed still matters
Knotweed spreads quickly through tiny fragments of rhizome – a piece the size of your little fingernail can create a whole new plant. While it rarely damages homes directly, it can affect outbuildings, hard landscaping, retaining walls and drainage.
More importantly: it affects lender confidence.
Most banks don’t want to finance a property where the risk hasn’t been assessed properly or managed professionally.
So yes – it’s a plant. But in conveyancing terms, it behaves more like a compliance issue.
The TA6 Trap (and what’s changed)
For years, sellers avoided giving a straight answer by ticking “Not Known” on the TA6, but that’s now over. The updated TA6 form now expects clearer disclosure around Japanese Knotweed – not speculation, but an honest statement based on what the seller reasonably knows.
Meaning:
- “Not Known” is no longer the easy escape route.
- A false declaration can expose sellers to misrepresentation claims.
If a seller has had knotweed in the past, had treatment, or knows of an infestation nearby, this is the moment it needs declaring.
The 7‑Metre Myth is gone
For years, we all lived by the “7‑metre rule” – if knotweed was within seven metres of a structure, lenders panicked. Then RICS rewrote the guidance. Now valuers are expected to look at:
- The extent and location of the knotweed
- Whether it’s managed or unmanaged
- Whether it presents a material risk to the property
- Whether it affects use, enjoyment or value
In short: the distance matters far less than the context.
Management is the new eradication
A decade ago, everything was about “total eradication.” The industry now recognises that knotweed can be managed effectively through long-term treatment plans. A good management plan usually includes:
- A site survey
- A multi‑year herbicide programme
- A guarantee
- Photographic records
- Insurance backing
Lenders want to see commitment and structure, not wishful thinking.
So, what do buyers actually need to know?
- Knotweed isn’t the catastrophe many tabloids painted it to be – if managed well.
- Professional treatment stabilises value and unlocks lending.
- Buyers shouldn’t panic, but they should insist on paperwork.
- Indemnity insurance can help, but only if the seller hasn’t contacted neighbours or raised awareness prematurely (easy mistake, costly consequence).
- Future liability sits with whoever owns the land now, not who planted it 20 years ago.
Handled early and transparently, knotweed becomes a manageable risk, not a deal‑breaker.
Japanese Knotweed is only a nightmare when it’s ignored. When it’s managed properly – with a clear plan, good documentation and open communication – most sales can progress smoothly.
Think of it as the conveyancing equivalent of seeing a warning light on a dashboard: Scary at first… but often an easy fix once you know what’s going on under the hood.
