Japanese knotweed
The seller says the knotweed was killed and the canes removed, but the survey still says possible because the ground is disturbed. Why is that not a category?
Because “possible” means the surveyor is not confirming the plant. Disturbed soil, old cane stumps or a cleared bed can be the reason for the caution. A possibility is not a RICS management category, and you should not award one to fill the silence. Dead canes in a skip are not a survey finding that the rhizome has gone.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
Knotweed is identified from the plant, not from a seller’s verb. Once the canes are cut and the bed is dug over, the visual evidence a surveyor uses may be gone, while the underground plant may or may not remain. The honest sentence is then that identification was not possible and the ground looks disturbed. A management category is a specialist judgement based on evidence of the plant and its impact. Guessing one from a raked bed invents a finding the surveyor withheld. Government guidance still says knotweed material and contaminated soil must not be spread. Digging to prove a point is how people cause that spread.
Ask the seller for any herbicide records, waste notes and a plan, and ask the surveyor what they saw: bare soil, cut stumps, or nothing specific. If there is no paperwork, say there is no paperwork. A lender may still want a specialist because the surveyor could not clear the plot. That is a request for identification, not a category you write in the margin. Do not let an agent change “possible” to “treated and clear”. Treated is a claim. Clear is a specialist’s conclusion after proper inspection. This visit has recorded doubt.
What should you ask your surveyor?
- What did you see that made you say possible, once the canes were gone?
- Are you assigning a management category? Please say if you are not.
- Did you see any paperwork on site, or only disturbed ground?
What are the typical next steps?
- Do not allocate a category the surveyor withheld.
- Ask for waste transfer notes and any treatment record rather than accepting “we killed it”.
- Do not excavate the bed yourself to hunt for rhizome.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Does disturbed ground prove knotweed was there?
No. People dig beds for ordinary planting. It explains the surveyor’s caution. It is not identification.
If a specialist later finds nothing, was the survey wrong?
Not necessarily. Possible means not confirmed. A later inspection with a different scope can close a question this visit left open.