Japanese knotweed

The report names Himalayan balsam by the brook and does not mention knotweed. Why is that still a spreading-plant note and not a knotweed mortgage form?

Himalayan balsam by the brook is still a spreading-plant note, and it is not a knotweed mortgage form. The report names balsam and does not mention knotweed. Balsam spreads along watercourses in its own right. Silence on knotweed does not fill in a knotweed form, and it does not prove knotweed is absent from the whole plot. GOV.UK guidance on invasive plants treats specified plants as themselves. The survey's finding is the balsam it named. The paperwork for knotweed is a different form, and this report has not produced it.

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?

Himalayan balsam throws seed and colonises banks. It is an invasive plant in its own right, which is why a survey bothers to name it beside a brook. That naming is not a code for knotweed, and it is not a mortgage form about knotweed. The plants are different, the risks are different, and the forms that ask about knotweed ask about knotweed. Leaving knotweed unmentioned means the report did not record knotweed. It does not mean a knotweed question has been answered for every metre of the garden.

The solicitor should see the balsam note as a grounds fact, and should not convert it into a knotweed declaration. GOV.UK guidance is about not letting invasive plants spread. It is not a knotweed certificate. If a lender's form asks specifically about knotweed, answer that question from what was identified, not by renaming the balsam. The survey has named one plant by the brook. It has not completed any other plant form.

What should you ask your surveyor?

Which plant did you name, and where?
Did the report mention knotweed at all?
Have you kept the balsam note off any knotweed form?

What are the typical next steps?

Keep Himalayan balsam as its own spreading-plant note.
Do not rewrite it as a knotweed mortgage form.
Answer any knotweed question from identification, not from this silence.

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

If the balsam is cut back, does the report become a knotweed all-clear?

No. Cutting balsam, if that happens later, deals with balsam. It does not search the plot for knotweed, and it does not turn this survey into a knotweed form. The report's plant finding remains the balsam it named by the brook.

Is balsam a grounds issue even when the house looks clear?

Yes. The note is about the plant by the brook, not about a crack in the house. A clear building does not delete a spreading plant on the bank. The survey has separated that grounds fact from knotweed paperwork, and it should stay separate.