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I do ‘knot’ need this!

japanese knotweed 02 3 12You might think it’s your noisy neighbours or a less-than-perfect bathroom that’s delaying the sale of your house but, in more and more cases, it’s down to an aggressive garden invader which is knot a laughing matter…

How very odd that an attractive plant with lush foliage and delicate flowers has become the cause of house selling and buying nightmares but, for many homeowners, this is the case. And the culprit? Japanese knotweed. The name is a bit of a giveaway – this plant, which was imported to the UK in the 19th century for ornamental gardens – is now one of the most damaging invasive species. It literally knots itself around, and grows through, anything. It even breaks up concrete: a major concern for homeowners.

True or False?
Panic reports in the press state that mortgage lenders ‘will not provide a mortgage on a property that has Japanese knotweed within 30 metres of a boundary’. However, contrary to this, some lenders will now issue mortgages if this destructive plant is within your home’s boundary, but not if it’s outside it. Why? Because if it is growing within your boundary, experts believe you are in a position to tackle the problem and solve it; outside of your boundary, it’s deemed much more difficult.

Take action
Mike Clough, the chief executive of Japanese Knotweed Solutions (, suggests ways to deal with the problem if this species is in your neighbourhood:

  • If you are aware that Japanese knotweed is in your local area, don’t wait until it’s on your doorstep. Ring your local authority; ring the landowner – make yourself a nuisance! You have to be vocal.
  • Note exactly where the plant has been spotted. Get some professional advice or take a tape measure and plot the position and distance the plant is from your property. The following year, carry out the same exercise and you will quickly get an idea of how rapidly the plant is heading in your direction.
  • While you carry out this exercise,  try to find the owner of the land and advise them that if their Japanese knotweed breaches the boundary of your property, you will be taking legal action – and use the measurements taken over previous seasons as proof of the origin of the infestation.
  • Take plenty of well-documented photographs and details of the precautions you have taken.

‘I didn’t think i’d ever sell my flat’
Dahlia Cuby, 38, a full-time mum, recalls her knotweed horror story

‘The sale of my flat was underway until my buyer’s mortgage company did a survey and spotted Japanese knotweed in my garden. I didn’t even know I had any – there were just two stems of it, about 20ft from my property. Her mortgage company immediately refused to proceed and I lost the sale. ‘I traced the plant’s origins – a passage that runs along the back of my row of houses. My flat’s leaseholder owned that land and he got specialists in immediately. They treated the knotweed with pesticide and it was left to die. The company returns twice a year for five years to check it’s not grown back and I was given a full report to show the works were complete. ‘I was advised to reduce my asking price by £30,000 but I resisted. I eventually sold it six months later but, in that time, Japanese knotweed completely took over my life.’

Get to the root of the problem

  • If you have space, fence off the infestation – allow a minimum of three metres from surface growth to fence line (seven metres is the recommended distance).
  • Treat repeatedly with a glyphosate- based herbicide such as Roundup. Continue treating until no new surface growth appears.
  • Leave the surface undisturbed for a minimum of 12 months.
  • Check for new growth.
  • Ideally, leave the root system in place and plant other species around the rhizome (where the roots grow horizontally along the ground).
  • Look for re-growth every year, even after you think you have eradicated the problem


This article was first published in at home with Sarah Beeny in December 2011. [Read the digital edition here]

Photograph: Getty Images

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