Living in fear of Japanese knotweed? Here are the facts rather than fictional frighteners!

publication date: Oct 27, 2016
author/source: Kate Faulkner, Property Expert and Author of Which? Property Books

Living in fear of Japanese knotweed? Here are the facts rather than fictional frighteners!

Halloween is looming and while you may no longer be scared of ghoulies and ghosties and things that go bump in the night, you may be haunted by bigger outdoor concerns.

And if you’re looking to purchase property, one of the scariest things people are starting to encounter is Japanese knotweed.

Described by the Environment Agency as “the UK’s most aggressive and destructive invasive plant”, Japanese knotweed spreads like wildfire – growing up to 4.5cm a day between April and October – and can damage drains, paths and walls. Its roots can penetrate the tiniest of cracks and it’s notoriously difficult to eradicate.

This is why lenders are now taking it pretty seriously and are on the lookout for it, insisting it is dealt with professionally if found, which could cost you or the buyer/seller thousands.

Got some home maintenance job to do? Read our expert checklist.

Fortunately, a new service has been made available to your legal companies, which will help reassure homebuyers about the risks of Japanese knotweed.

Launched by STL, one of the largest property search companies in England and Wales, the unique Japanese Knotweed Hazard Alert automatically notifies legal companies of the level of Japanese knotweed risk in every residential property transaction.

This free alert identifies if the risk is low, medium or high and is based on exclusive data from the Centre for Ecology & Hydrology.

Once the risk factor is known, legal companies can then recommend the associated insurance policy, provided by CLS Risk Solutions, which offers up to £20,000 towards financial loss if Japanese knotweed is found at the property within five years. It covers treatment of the weed, repair work to your property, legal fees and expenses, as well as any loss of market value to your home.

Got some home maintenance job to do? Read our expert checklist.

Homebuyers should consider Japanese knotweed, just as they would consider the risk of flooding when purchasing a new home,” say STL. They point out that, as well as affecting a home’s value, the presence of Japanese knotweed can harm its saleability and a buyer’s chances of getting a mortgage.

What’s more, it’s an offence to allow it to spread and, if you fail to prevent the plant from spreading to your neighbour’s property, they can legitimately sue you.

Alan Thorogood, CEO of STL, says: “Finding Japanese Knotweed on your property is hugely stressful, not to mention the impact on the value of your home. Homebuyers, can now, for the price of a weekly grocery shop, future-proof themselves against the damage and the worry of the UK’s most aggressive and destructive invasive plant.”

Seriously scary Japanese knotweed facts

  • According to the Financial Times, Japanese knotweed (fallopia japonica) costs the UK more than £160million a year.

  • Its roots can spread up to three metres deep and a staggering seven metres across.

  • As well as causing problems to property, the plant can affect flood defences and, due to its invasive nature, harms biodiversity.

  • To get rid of it, herbicides need to be used on the visible parts of the plant repeatedly for three years.

  • Because it can regrow from the smallest piece of root, Japanese knotweed is classed as controlled waste under the Environmental Protection Act 1990 and must be disposed of at licensed landfill sites.

  • According to the government, you could be fined up to £5,000 or imprisoned for up to two years if you allow contaminated soil or plant material to spread into the wild.

If you do find Japanese knotweed on your property, there are lots of specialist companies out there who will help, but be sure to use a member of The Invasive Non-Native Specialists Association (NNSA), the industry body for companies involved in controlling and eradicating such weeds. For more information, visit

Read more about controlling Japanese knotweed here:


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