Fewer than one in five can identify Japanese knotweed

Published by Hannah Nemeth on 11 July 2018.
Last updated on 11 July 2018

Japanese knotweed

Fewer than one fifth (19%) of Brits who say they are aware of Japanese knotweed can correctly identify the weed, according to a YouGov poll.  

The research, commissioned by knotweed removal firm Environet, comes in the wake of a landmark ruling that found in favour of two homeowners who claimed that Japanese knotweed had damaged their properties.

If people don’t recognise this invasive plant, it could result in it damaging theirs and neighbouring properties. It could also result in property sales falling through if knotweed is only recognised when buyers arrange a survey.

When asked to pick out Japanese knotweed from a selection of five photographs, 81% of the 2,000 people polled were unable to correctly identify it, with 14% mistaking it for bindweed, 8% selecting houttuynia, 5% Russian vine and 6% confusing knotweed with ivy, found in most British gardens.

When it comes to selling their property, the good news is that 75% of those polled would do the right thing and have the knotweed professionally treated prior to the sale. However, 4% say they would try to conceal it from a potential buyer. Environet says that, based on the fact that an estimated 2% of properties in the UK are directly affected by knotweed, this could result in around 1,000 cases each year of knotweed being concealed during property deals.

Only 36% of respondents know that they could be sued if they allow Japanese knotweed to encroach on to a neighbouring property and just 18% understand they could face prosecution under an anti-social behaviour order.

Meanwhile, only 12% of respondents knew that a treatment plan with an insurance-backed guarantee needs to be in place in order to secure a mortgage on a property affected by Japanese knotweed.

Nic Seal, managing director of Environet, says: “Most people have heard of Japanese knotweed but the fact that only 19% of Brits aware of the weed can identify it from other common plants, such as bindweed and ivy, is very concerning. 

“If left untreated Japanese knotweed will grow rapidly, by up to 10cm a day during the summer months, pushing up through cracks in concrete, cavity walls and drains and causing damage to property. The longer it is left, the further its underground root system will spread and the costlier it will be to tackle.

“The good news is that Japanese knotweed can be treated, either over two to three years using herbicide methods, or immediately by excavating it from the ground. With an insurance-backed guarantee secured for the work, transactions should proceed unhindered.”

Environet offers a free Japanese knotweed identification service where homeowners who are worried about a plant can send a photograph for review at expert@environetuk.com. If knotweed is identified and a homeowner wants a quote, it will be provided - but the company says there is no obligation. 

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No reputable Japanese

No reputable Japanese knotweed contractor will partake in the hysteria narrative of the species. With research taking place and the highly publicised landmark ruling in the Network Rail case, conversation around knotweed is coming to the fore, and seems to be, on the whole, from a different angle to the “invasion of the alien knotweed” Daily Mail nonsense of times gone by. Ecologists from AECOM and the University of Leeds have reportedly found no evidence that Japanese knotweed causes significant structural damage. Where does this stigma come from? A general reluctance to lend mortgages on affected properties along with RICS guidance on Japanese knotweed in terms of its proximity to built structures was based on the knowledge that the species’ rhizomes spread as far as seven metres laterally and therefore, if close enough, could damage the integrity of said built structure. Property values have been affected by this considerably. However, this new research arguably blows this out of the water. Dr Karen Bacon of the University of Leeds said this:
“Japanese knotweed is capable of damaging built structures, but where this occurs, it is usually because an existing weakness or defect has been exacerbated.” Will this research alleviate any of the frenzy surrounding Japanese knotweed? All research in the field should be welcomed and the discussion widened to include studies such as this to separate facts from scaremongering in the media. It is ultimately our duty as a professionals and reputable Japanese knotweed contractors to be honest and clear with our clients at all times. Japanese knotweed does pose many problems to biodiversity and creates a barrier to development, and these issues should be conveyed truthfully.