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09 Jul 2018 < Back

Trade association sets the platform for debate around new Japanese knotweed findings

A national trade body says a new study into Japanese knotweed reinforces the fact the invasive weed’s impact on property is at odds with its reputation in the UK.

According to the Property Care Association (PCA), research led by Dr Mark Fennell and Professor Max Wade of AECOM, together with Dr Karen Bacon of the University of Leeds, could help remove some of the negativity and sensationalism surrounding the plant.

Now the findings are scheduled for in-depth discussion at the trade body’s Invasive Weed Control Conference later this year.

Stephen Hodgson, chief executive of the PCA, said: “We welcome this research, which we have supported in its development.

Japanese knotweed-Fallopia japonica

“The paper addresses important questions which have an impact on the calculation and assessment of risk where Japanese knotweed is found in close proximity to buildings.

“The findings show that, although the invasive weed is a fast growing and highly invasive species perfectly capable of causing disturbance to areas such as paths, patios, driveways and garden walls, it is an herbaceous perennial, which lacks the potential to cause significant disturbance to normal building foundations.

“The paper is an authoritative and independent confirmation of the PCA’s Code of Practice which states that, where Japanese knotweed is found alongside buildings, it can normally be treated in situ without the need for any urgent structural works or precautionary preventative actions to protect buildings from physical impacts.

“Despite the fact there are clear pathways to manage and control Japanese knotweed, all too often we encounter situations where homeowners are portrayed as living under siege with the plant.

“But since the PCA formed the Invasive Weed Control Group in 2012, we’ve always maintained the position that this plant is not a destroyer of buildings, and that it should just be regarded as any other type of property issue.

“The research could raise interesting questions on how Japanese knotweed is viewed in the future by organisations including the Royal Institution of Chartered Surveyors, as well as banks and mortgage lenders.

“It also needs to be considered in light of the Court Of Appeal ruling against Network Rail this month (July) which means landowners will be able to claim damages if Japanese knotweed encroaches on their property.

“Both the research and the Court of Appeal decision will form a core element for discussion at our forthcoming Invasive Weed Control Conference later this year, where we will welcome a refreshed academic debate on the subject.”


Insight into the research and the Court of Appeal case will be presented at the conference, which takes place this year at The Slate, University of Warwick on 22 November.

More details about the event can be found at

Earlier this year the PCA also supported research from Swansea University, which revealed that Japanese knotweed was difficult to kill.

Mr Hodgson added: “Again, these findings align with the cautious approach we have publicised in our Code of Practice and in our industry best practice.

“We are sharing the findings across our membership and will be looking in particular at the reference to the most effective timings for treatment, as this will be an important element of us continuing to develop best practice.

“Ultimately, we need to continue the debate around Japanese knotweed to ensure the approach we take is measured, fit-for purpose and is built on the latest information we receive.

“Research is a key element in that approach and is something we will to continue to support, to give homeowners and mortgage lenders confidence in the issue.”


About the PCA

Noted for its training and technical expertise, the PCA incorporates the British Wood Preserving and Damp-proofing Association (BWPDA), which has been in formation for more than 85 years.

The trade body represents the UK’s invasive weed control industries, as well as the structural repair sector, structural waterproofing, wood preservation, damp-proofing and flood remediation industries.

Press release issued by Jane Shepherd, Shepherd PR Limited, 01538 308685, 07985 129315



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