Can Japanese Knotweed kill a mortgage deal?

My parents are buying a house in north London but apparently they may have difficulty getting a mortgage, as the garden contains Japanese Knotweed. How is this possible?
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Question: my parents are trying to buy a house in north London but the estate agent says that if they need a mortgage they may be in some difficulty, as the garden is believed to contain Japanese Knotweed. How can a plant have any affect on whether a mortgage is going to be granted?

Answer: this extremely invasive species of plant can damage property including drains, walls, paths, driveways, outbuildings etc, and as such is a concern for lenders.

It is not an offence to have Japanese Knotweed on your land. However, it is a criminal offence to plant it, or otherwise cause it to grow in the wild. In fact all reasonable steps should be taken and due diligence exercised to avoid spreading the plant.

The property information form that a seller completes when marketing their home has a section on Japanese Knotweed. The seller must disclose whether the property is affected by the plant, and if it is, they must also say whether a management plan is in place to deal with it, and provide a copy of any such plan.

Furthermore, a valuer carrying out a mortgage valuation for a lender must note on their report if Japanese Knotweed is present.

Some lenders may automatically refuse to lend where there is a presence of Japanese Knotweed, while others will lend but will wish to know there is a treatment plan or management plan in place, and will usually require an insurance-backed guarantee. Most lenders will look at each case individually and will consider their valuer's comments.

Do remember that in view of the invasive nature and rapid spread of Japanese Knotweed, it can be an issue for lenders even when it is only present in a neighbouring garden and not actually in the garden of the property to be mortgaged.

If you have a question for Fiona McNulty, please email or write to Legal Solutions, Homes & Property, London Evening Standard, 2 Derry Street, W8 5EE. 

We regret that questions cannot be answered individually but we will try to feature them here. Fiona McNulty is a partner in the residential property, farms and estates team at Withy King LLP (

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