It’s all very well cleaning the windows and painting the walls, but if you have Japanese knotweed in your garden, you’ll find buyers could run a mile. Here’s how to beat this fast-growing weed
The presence of this invasive plant can threaten a property’s foundations, impact on its value – and in some cases make it almost impossible to sell.
It is not unusual for lenders to refuse to lend on a property if the weed has been found, while others will put strict conditions in place and force you to agree to a treatment plan and insurance.
Here we take a closer look at what the presence of Japanese knotweed means when you’re trying to sell up – and what you can do to improve the chances of your sale going through.
What is Japanese knotweed?
Japanese knotweed is a notorious non-native species that has been thriving in the UK since its introduction in the 1820s as an ornamental plant.
A fast-growing weed that chokes out other greenery, it has a root system considered to be strong enough to grow through asphalt, cracks in concrete, drains and cavity walls. If left to spread, it can potentially threaten the foundations of buildings.
Eradicating this troublesome weed is a far from simple task because cutting it down can simply cause it to grow back fast.
Issues if you are trying to sell
In the UK, Japanese knotweed is widely believed to pose a significant risk of damage to buildings that are within seven metres of the parts of the plant that are above ground.
Paula Higgins, chief executive of the HomeOwners Alliance, says: “Japanese knotweed is a huge headache for homeowners, and the impact it can have on your ability to sell can be much more serious than you might have thought.
"This invasive weed has a root system that can spread wide and, if it reaches a property, it can cause damage to the foundations.”
Lenders may refuse to lend
If your buyers carry out a survey that finds that the plant is less than seven metres from your home, their lenders may get jumpy.
Many lenders have policies that restrict their ability to lend against a property that has the weed growing in the garden. And those that are willing to lend will usually insist on seeing evidence that a full treatment plan from a knotweed contractor has been put in place, together with a 10-year insurance-backed guarantee against its return.
Lenders may stipulate that you use a contractor that is registered with an organisation such as the Property Care Association (PCA) or the Invasive Non-Native Specialists Association (INNSA).
Peter Mugleston, managing director of Onlinemortgageadvisor.co.uk, says: “Some lenders will refuse point blank to lend if a property has a knotweed issue.
"At the very least, most will want to know that treatment is being undertaken to control the knotweed before they’ll agree to lend.”
Take note, however, that while professional removal programmes may offer a solution, the treatment does not come cheap.
Findings from the Crop Protection Association (CPA) show the average cost for homeowners after knotweed appeared is £1,880, while one in 10 faced costs of more than £4,000.
'My management plan saved the sale process'
Liz Betteridge was able to successfully sell her home despite having Japanese knotweed in the garden after she put a management plan in place that kept both her buyers – and their lender – happy.
The 53-year-old had lived in her three-bedroom property in Torquay, South Devon, for around 17 years before putting her home on the market in 2016.
“Japanese knotweed had been present in the garden the whole time I lived there, and gardeners who had come to do work for me had warned me about it,” says Liz. “But I wasn’t too worried as there were only a few shoots on one site located further down the garden and the plant wasn’t affecting my home in any way.”
When Liz was preparing to sell her home, she started doing a lot of research into Japanese knotweed on the internet.
“I read all the horror stories, but I was determined not to get sucked into all the panic and hype,” she says. “I’d read about the importance of having a management plan in place to make a property sellable, and got in touch with the Japanese knotweed removal specialist Environet.”
Liz instructed the firm to treat the knotweed using herbicide. “The first application happened that summer, and a second application took place the following year,” she says. “A third ‘check’ visit was scheduled for the third year to make sure there had been no regrowth.”
The site visit and treatment cost Liz around £5,000 in total and included a guarantee.
“This was quite expensive, but I saw it as a ‘treatable nuisance’ and a cost that I just had to pay as part of my moving costs,” she says. “Things went well, and I was able to market my home and find a buyer.”
Liz asked her estate agent to be upfront to the buyers about the Japanese knotweed in her garden, as she didn’t want the issue rearing its head further down the sale process – possibly causing the buyers to pull out.
“But I also asked my estate agent to explain to the buyers that I was dealing with the problem,” she adds. “And, with a management plan in place, the buyers weren’t deterred – and neither was their lender – and the sale went through without a problem. It was a big relief.”
Cutting down this invasive weed can simply cause it to grow back fast
Risk that buyers will pull out
In some cases, buyers will pull out at the mere mention of Japanese knotweed, while others will withdraw their offer further down the line owing to difficulties in getting a mortgage. Not only this, but the weed's presence can knock tens of thousands of pounds off the value of a property.
Further findings from the CPA show that one in seven people with knotweed saw a property deal fall through as a result, while one in five saw the value of their house drop.
In the worst cases, Japanese knotweed can render a property almost unsaleable.
Is the problem overhyped?
While this may make for gloomy reading, a recent study from global infrastructure services firm Aecom and the University of Leeds raised doubts over just how damaging Japanese knotweed is – and suggested that it may pose no more of a threat to property than many other plants.
Dr Mark Fennell, principal ecologist at Aecom, says: “We found nothing to suggest that Japanese knotweed causes significant damage to buildings – even when it is growing in close proximity – and certainly no more damage than other species that are not subject to such strict lending policies.”
The research goes on to say that automatically refusing mortgages on properties where the plant is found is “out of proportion to the risk posed by this invasive species”.
According to the findings, knotweed only causes problems where a property already has existing structural faults. In response to this, lenders are being encouraged to reassess their stance on knotweed.
However, you shouldn’t expect lenders to change their approach to knotweed any time soon.
Jane Erskine, deputy property ombudsman at The Property Ombudsman, says: “Despite this new report suggesting knotweed is relatively harmless to properties, its presence has – and probably still will – affect residential property sales.”
"If you do find the weed, take action before marketing your property”
What action should you take?
If you do find the dreaded weed on your property, you need to take action to tackle the problem before marketing your property. Nic Seal, managing director of Japanese knotweed removal specialist Environet, says: “Sellers have a legal obligation to disclose if their property is – or even has been – affected by knotweed, as a direct question is now part of the TA6 property information form.
"Those who are dishonest are leaving themselves wide open to legal action from the purchaser once they come to realise that the property is blighted by the weed.”
Crucially, you should never try to remove knotweed yourself, as you may inadvertently cause it to spread. Instead, you should instruct a professional firm to treat the plant, remove it, and dispose of it safely.
You should check that your chosen firm offers an insurance-backed guarantee lasting for at least 10 years, which transfers with the ownership of the property.
Japanese knotweed removal specialists include Environet (https://environetuk.com) and The Knotweed Experts (theknotweedexperts.co.uk); the latter recently launched a 35-year guarantee, which ensures that homeowners are now covered for the entire length of their mortgage.
Treatment options for knotweed include 'excavation', which is an instant fix, removing the plant within a matter of days; this involves the whole area being dug out. The alternative is herbicide, which is cheaper, but can take up to three years to complete.
Provided there is a planned eradication programme in place, lenders should be happy to proceed – and nervous buyers should be reassured.
Mr Seal adds: “While the knotweed will still need to be declared, this will keep most buyers and lenders happy – and will give you the best chance of a smooth, successful sale.”
Cases at the Court of Appeal
In a recent landmark case, the Court of Appeal ruled in favour of two householders whose properties had suffered from Japanese knotweed encroaching on their gardens from neighbouring land that is owned by Network Rail.
This court ruling has stimulated discussion as to whether landowners can claim damages if the plant has spread to their property.
Paula Higgins, chief executive of HomeOwners Alliance, says: “In future, homeowners may be able to sue their neighbours to cover the costs of removal and loss of value.”
ESTHER SHAW is a freelance journalist who writes about money and property for The Guardian, Observer and the Sunday Sun