Japanese knotweed

Himalayan balsam lines the brook at the foot of the garden and knotweed is not mentioned. Why is that still a plant the survey should not rename as knotweed?

Because it is Himalayan balsam, and renaming it as knotweed would name a plant the survey did not record. Knotweed is not mentioned. Balsam along the brook is the plant that was seen. They are different species. GOV.UK guidance on invasive non-native plants is about not letting those plants spread. It does not ask a survey to collapse every invasive plant into Japanese knotweed. The report should keep the name of what was there. Balsam is already a plant to take seriously. It is not knotweed by another word.

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?

Balsam likes a brook edge and can dominate a bank. Knotweed is the plant lenders ask about by name. Calling the balsam knotweed would send everyone after the wrong plant and would invent a record the survey did not make. Dropping it, because it is not knotweed, would ignore an invasive plant the guidance says not to spread. The accurate note is balsam along the brook, with knotweed not mentioned.

Tell the solicitor the plant recorded is Himalayan balsam, not knotweed, and that knotweed was not mentioned. If you need advice on the brook, ask someone who will deal with balsam as balsam, and follow the guidance not to spread it. Do not let a mortgage question about knotweed be answered by renaming this plant. The home survey has not identified knotweed here and has not told you to pretend the balsam is something else.

What should you ask your surveyor?

What plant did you record along the brook, by name?
Did you mention Japanese knotweed, or was that plant not the finding?
Are you keeping balsam and knotweed as different plants in the note?

What are the typical next steps?

Keep the brook plant named as Himalayan balsam.
Do not rename it as Japanese knotweed.
Treat it as an invasive plant in its own right, not as a blank.

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Also asked about this

If a lender only asks about knotweed, can the balsam be left off the form?

The lender's knotweed question is about knotweed, which was not mentioned. That does not make balsam disappear from the survey. The survey should not rename it, and it should not drop it. Answer the knotweed question from the knotweed facts, and keep the balsam note beside it. They are different plants. GOV.UK's invasive-plant guidance still applies to the balsam.

Does balsam on a brook mean knotweed is usually there too?

Not as a rule this survey can use. The finding is balsam along the brook, and knotweed is not mentioned. One plant does not prove the other. Renaming balsam, or adding knotweed because the bank looks weedy, would go beyond what was seen. Record the balsam. Do not invent a knotweed stand the report did not record.