Worried about Japanese Knotweed on neighbouring land

Q: I've recently purchased a property and about three weeks after completion, I discovered Japanese knotweed growing on council land adjacent to my property on the other side of the boundary wall. The council have acted quickly and have already sent out contractors to start a treatment programme. However I'm looking for some advice to protect my own property, as advised by my solicitor who did the conveyancing for me. My mortgage broker sent a general enquiry to my mortgage lender who said that I will need to prove the knotweed has been eradicated when I come to remortgage in five years' time. Although there are currently no visible signs of knotweed on my land, I'm wondering whether it would be advisable to have an independent survey to assess the risk. I don't want to start paying for a treatment programme until there is something they can actually treat and I want to make sure that any treatment programme is acceptable to mortgage lenders.


In theses circumstances, I would advise the person worried about Japanese Knotweed to first to ask the council for details of the extent of the problem as discovered and how it has been dealt with and by whom. Ideally the course of action undertaken will have been in accordance with a specified risk assessment and the council can hopefully confirm this one way or another.

If as consequence of this no treatment works were required then this would be fine, and a letter to support this should suffice for future reference.

But if works were required and undertaken/ongoing then your member should request the council to provide documentary evidence of what has been undertaken so far and details of the management programme.  She should also find out if the works are covered by an insurance-backed approved guarantee.   Again, this may suffice for future reference.

In the event of any doubt, she might wish to commission a report from a Japanese knotweed specialist – the following organisations should be useful in sourcing an expert:

  • Property Care Association
  • Royal Horticultural Society
  • Invasive Non-Native Specialists Association

Apart from this, the Environment Agency site is a useful source of information on Japanese knotweed and other invasive species too – see www.gov.uk/japanese-knotweed-giant-hogweed-and-other-invasive-plants.

As you can see it is an intense subject which can scare the living daylights out of people, but more often than not can be demystified and managed although maybe involving some cost.

Graham Ellis BSc(Hons) MRICS, Director, Greenhouse Surveyors, Southport



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