Two words that will inject a state of fear and anxiety in any homeowner or buyer are Japanese Knotweed. But is this legendary concrete-smashing, tarmac-raising plant really worth getting your Kimono in a twist over?

Quite possibly. If a surveyor discovers Japanese Knotweed on the premises, it may well indeed put your buyers off. In addition, some mortgage providers will not approve borrowing, or will want a guarantee of an effective treatment programme. Presence of the non-native plant can also threaten to wipe thousands off your asking price.

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It’s not a complete disaster though. Let’s take a look at the facts so you can plan what you need – and should– do about Japanese Knotweed.

  • The distinctive bamboo-like plant (though not related) is listed by the World Conservation Union as one of the world’s worst invasive species.
  • Its root system and strong growth can, in extreme cases, damage concrete foundations, drainage systems and walls, as well as strangle other plants.
  • It has a large underground network of roots (rhizomes) which need to be killed to destroy the plant. It can take three years of regular herbicide treatment to render it ‘dormant’.
  • You don’t have to remove or control it by law, but you could be prosecuted for causing a nuisance if Japanese Knotweed in your garden spreads to neighbouring properties.
  • It’s a criminal offence to plant it or cause it to grow in the wild – for example, by not disposing of plant or soil waste properly. You could be fined or go to prison for up to two years.


All in all, this graceful, innocent-looking plant isn’t something the unsuspecting homeowner or gardener wants responsibility for.


How to get rid of Japanese Knotweed

  1. Start as soon as possible.
  1. Even if you need to sell your house fast, home buyers and mortgage providers might be happy to go ahead with buying your house if they have a guarantee that the situation is being handled by experts, so you might try an approved specialist like Environet or TP Knotweed Solutions to ensure the situation is controlled and handled correctly.
  1. Picking the right herbicide is essential, as it must travel through the plant and into the root system below. If you’re planning to go into mortal combat with the plant yourself, use a total weedkiller, such as glyphosate.
  1. Cut away old stems in winter and spray the plant in late summer when the weed is flowering. You’ll need to re-apply in midsummer, evaluate in September and spray again if needed. Then check again the following spring. Because even after all that it can take a few seasons to eradicate using glyphosate.
  1. Never, ever, put any cut stems or roots into green waste bins or domestic – because the 1981 Wildlife and Countryside Act made it illegal to plant Japanese knotweed in the wild or to allow it to grow by careless disposal. It’s much safer to take them to a licensed waste site.


The future for Japanese Knotweed

The Royal Institution of Chartered Surveyors (RICS) published a report in 2012 in response to lenders refusing to lend despite knotweed being treatable and rarely causing severe damage to the property:

“There is a real lack of information and understanding of what Japanese knotweed is and the actual damage it can cause. […] surveyors have been unsure of how to assess the risk of Japanese knotweed, which can result in inconsistent reporting of the plant in mortgage valuations.

“RICS hopes that this advice will provide the industry with the tools it needs to measure the risk effectively, and provide banks with the information they require to identify who and how much to lend to at a time when it is essential to keep the housing market moving.”

Philip Santo, RICS Residential Professional Group

So as long as you’ve identified the plant before it has managed to cause damage, it will take a bit of money and effort but your property will be okay. Our advice would be to remain pragmatic and seek out the help and advice you need.

For more tips about selling your house, see our recent article detailing the ways you can speed up your conveyancing.


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