Japanese knotweed
Does a seller’s note that herbicide was sprayed mean the knotweed category is now clear?
No. A note that someone sprayed is not a management category, and it is not evidence the plant has gone. The 2022 journal still expects knotweed that is seen to be reported, and it expects a remediation specialist to advise on action. Ask for the management plan, the dates and the guarantee, if any exist.
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?
Herbicide programmes often run over more than one growing season. A single visit by a surveyor cannot see whether rhizome is still alive. Dead top growth can be the point of the treatment or a sign it has not worked. The paperwork matters: who treated it, against which standard, and whether a guarantee is still in force and can transfer. The survey will not verify a guarantee with the insurer.
GOV.UK warns against letting the plant spread and against treating contaminated soil as ordinary waste. Spraying does not licence you to dig. If the plan is missing, the honest position is that treatment is claimed but not evidenced. Do not let a seller’s sentence delete the surveyor’s category.
What should you ask your surveyor?
- What paperwork should the specialist have produced, and have you seen it?
- Are canes still visible, or only a seller’s claim?
- Does any guarantee transfer to a buyer, or do you not know?
What are the typical next steps?
- Ask the seller for the plan, the invoices and the guarantee, and read the address and the expiry.
- Ask the specialist named on the paper whether they will confirm the programme to you.
- Do not dig the area to “check” and then try to bag the soil with the garden waste.
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 a five-year guarantee mean five years of visits happened?
Not unless the paper and the specialist say so. Read the schedule. Missed visits matter.
Can the surveyor sign the guarantee off?
No. The surveyor reports the site. The guarantee sits with the firm that issued it.