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Re-development, roadworks and rivers are helping to spread highly invasive Japanese Knotweed across Wales. And commercial and residential property owners need to be extra vigilant following a warm and wet Spring which has created optimum growing conditions for the plant.

The warning comes from Nick Worman at Bruton Knowles’ Cardiff office, who said the highly invasive weed could appear in a fairly short period of time, particularly during the prime growing season.

He said regular inspections of properties are essential.

“The problem is particularly prevalent in South Wales as we have plenty of potential transmission routes, particularly rivers and roads. Regeneration and other development including road building involves lots of earth moving and that is where the plant can also be spread and flourish.”

He went on: “We have recent experience of this issue in Swansea, where a property that we valued was rejected by several banks even though the Japanese Knotweed was outside the property boundary and some distance from the property itself. Japanese Knotweed can grow up very quickly despite regular inspections.”

“Our Swansea case was probably the result of construction works related to the dual carriageway that runs immediately to the rear of the property concerned.

“South Wales also has lots of brownfield land which is more at risk than greenfield sites.

“We’ve seen development sites adjoining rivers where the first thing the developer does is remove all the top soil, including the Japanese Knotweed that runs along the adjacent river bank, and dumps it in a heap ready for re-use across the development as the houses are built.”  

Nick said banks and lenders were becoming increasingly wary of lending on properties where the plant was present due to the potential disruption it could cause - unless there was a commitment from the owner to treat and remove the plant.

“Many mortgage lenders seem prepared to take a pragmatic view where infestations occur - but there is no guarantee this will be the case. We are aware of a number of lenders who will reject mortgage applications in such circumstances.”

The issue affects properties close to infestations, not just properties directly affected by Japanese Knotweed.

“A common ignorance of how the weed is spread means that many property owners, local authorities, developers and contractors frequently spread it through inappropriate landscaping, earthmoving and treatment strategies.”

“The worst thing you can do is to ignore the problem.  This makes no sense as even a small infestation can take thousands of pounds to eradicate successfully and/or an extended.

“Leaving an infestation untreated will allow increasing spread and potentially an exponential increase in cost of remediation. In Swansea alone, this amounts to many millions of pounds.”

Japanese Knotweed spreads 2-3 metres below ground and also potentially the same distance beyond any visible growth.

A number of well-established contractors offer eradication programmes either immediate or over a number of years based on chemical treatment or screening and removal of JK plant material from affected soil. They should be members of a recognised trade body and ideally also offer an insurance backed guarantee on completion of the eradication programme.

For further information contact Nick Worman on 02920 028800 or This email address is being protected from spambots. You need JavaScript enabled to view it.















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