Japanese knotweed

Should giant hogweed, seen beside the stream bank, be treated as a verdict on knotweed, which is a different plant?

No. Giant hogweed beside the stream bank is not a verdict on Japanese knotweed, because they are different plants. The survey saw hogweed, or growth consistent with it, at the bank. It has not decided that knotweed is present, and it has not cleared the bank of knotweed either. One invasive plant does not stand in for the other. The finding is limited to what was visible of the hogweed. Anything else on that bank stays untested by this identification.

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?

Giant hogweed is a tall umbellifer with a sap that can burn skin. Japanese knotweed has cane-like stems and a different growth habit. Both can appear on stream banks, and both are invasive non-native plants that official guidance treats seriously, but seeing one is not a determination of the other. A home survey records the stand it can see. It does not run a botanical laboratory test, and it does not dig the bank to prove what else is in the soil. The names must stay apart.

Tell the solicitor that hogweed was noted at the bank, and that knotweed was not identified from it. If you need the bank checked for knotweed as well, that is a separate look by someone instructed for invasive plants, not a rereading of this note. Do not handle the hogweed yourself. Do not let a seller's reply about knotweed be treated as an answer about the hogweed, or the other way round.

What should you ask your surveyor?

Where on the bank was the hogweed growth actually seen?
Did any stem match knotweed rather than hogweed?
Who, if anyone, has been asked to survey the bank for both plants?

What are the typical next steps?

Keep hogweed and knotweed as separate findings.
Tell the solicitor the note is about hogweed at the bank.
Instruct a plant specialist if you need the bank checked for knotweed too.

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

Did the home survey laboratory-test the sap?

No. The survey recorded what was visible of giant hogweed at the stream bank. It did not test sap, and it did not identify knotweed from that plant. Looking is not a lab result. Treat the note as a visual record of hogweed only.

Should the bank be assumed clear of other plants?

No. Seeing hogweed does not clear the bank of knotweed or of anything else. The survey has not excavated and has not claimed a full plant list. Other growth stays untested. A specialist look is a further instruction if you need that wider check.