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Could you identify Japanese knotweed and save your property?

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Springtime is traditionally the busiest time for the property market, but with a knotty problem affecting more homes than ever, it’s worth doing some horticultural homework before you start, whether you’re buying or selling.  Sarah Brooks, Residential Conveyancing Partner, here reviews new research highlighting the financial impact Japanese knotweed can have on a property, and advises how home owners and potential buyers can take action against this de-valuing plant.

What is Japanese knotweed?

Japanese knotweed is a highly invasive, aggressive and destructive plant, able to grow as high as four metres in just a few months and with roots that can spread seven metres.  It’s non-native with no natural predators, and can lead to structural damage to buildings due to its’ ability to grow through concrete and tarmac, damaging walls, drives, drains etc.  The plant is known to spread rapidly, and if ignored and left to grow, it can be expensive to either remove or fix the damage it leaves behind.   Removing it however is a costly and time-consuming business which involves specialist waste disposal; simply digging up the roots is not enough to kill it. 

“Recent research conducted by Crop Protection Association has revealed that 15% of homeowners saw a property deal fall through due to a knotweed infestation,” begins Sarah.  “A further 20% saw a drop in their house value because the plant was present, and two thirds of UK mortgage brokers have reported that Japanese knotweed has negatively impacted transactions.  In these cases, many are forced to withdraw mortgage applications.”

Japanese Knotweed Control, invasive plant experts, will shortly be launching a campaign to educate property professionals on how to recognise the plant so they can raise awareness to home owners and potential buyers.  “Spotting Japanese knotweed can be tricky, and it is a plant which is regularly incorrectly identified,” explains Sarah.  “Things to look out for include zig zag stems, lush green coloured leaves, shield shaped leaves with a flat base, bamboo style stems, and red tinged shoots.  It would generally be found in dense clumps, and in the summer months it will sprout clusters of white flowers.”

Growth of Japanese knotweed

“If you are looking to buy a property, even if the seller has stated that it is not known or a definitive no to Japanese knotweed being present, you should ask your own surveyor or a horticultural expert to confirm this,” continues Sarah.  “It may also be in your interest to investigate with the seller that if the plant is not present in their own grounds, whether it is known to be a problem in the neighbourhood due to the prolific spreading of the plant. If you are obtaining a mortgage to purchase the property your Lender may not wish to lend on a property with Japanese Knotweed. Alternatively, they may lend if there is a treatment schedule in place and a Completion Certificate that confirms the weed has been remediated with a Guarantee in place for a minimum of 10 years.”

If you allow contaminated soil or plant material from Japanese knotweed spread into the wild, you could be fined up to £5,000 or sent to prison for two years.  “If you can see Japanese knotweed growing then take steps to eradicate it”, explains Sarah.  “If it’s growing on neighbouring properties, speak with your neighbours, and if they don’t tackle the problem then it’s worth considering action.  If you are successful with a nuisance claim, you can push for neighbours to undertake a five-year eradication programme and ask for a guarantee from the specialist company involved, as well as seeking compensation, if there is evidence it has travelled through your boundaries.” 

Sarah concludes, “Taking action to protect what is probably your biggest asset is a simple but sensible option, whether you’re buying, selling or staying put.  These days, when you sell a property, you will be asked whether Japanese knotweed has been found on the property and the reply will be included in the comprehensive pack of buyer’s information that lawyers compile during the conveyancing process.”

If you are considering buying or selling your property and have questions about Japanese knotweed or the process in general, you can contact Sarah or the team by emailing


This is for information purposes only and is no substitute for, and should not be interpreted as, legal advice.  All content was correct at the time of publishing and we cannot be held responsible for any changes that may invalidate this article.