Japanese knotweed

What should you stop a gardener doing if the survey says Japanese knotweed may be present?

Stop them strimming, mowing the clump into the lawn and taking the cuttings away as green waste. GOV.UK says you must not cause Japanese knotweed to spread, and fragments are part of that risk. A home survey does not supervise the garden. A tidy lawn the week before exchange can be how the evidence disappears and the plant is spread.

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?

Strimming chops the cane and flings pieces. That is not treatment under a management plan. The 2022 RICS approach, described in the journal, expects identification and specialist advice when the plant is there. Herbicide, digging and guarantees are the specialist’s method, not a Saturday tidy. The survey category, if one was given, is not a work instruction to the gardener.

If the seller has already strimmed, say so to your solicitor and to any specialist you instruct. The absence of tall canes is not a clear site. There is no RICS price for a proper treatment. Do not pay a gardener to “finish it” before completion.

What should you ask your surveyor?

Did you see cut canes, or standing growth?
Are you identifying knotweed or only warning that it might be?
What should not happen to the garden before completion?

What are the typical next steps?

Write to the agent that the bed should be left alone.
Do not strim it yourself on a second viewing.
If it has been cut, tell the specialist. Do not assume it has been treated.

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

Is pulling the canes by hand any better?

It can still snap and spread material, and it is not a management plan. Leave it.

Does a strimmed bed become category C?

No. Categories are not awarded for tidiness. A cut stem is not a completed treatment.