Recent research by AECOM and the University of Leeds provides sound evidence that Japanese knotweed is no more damaging to buildings than other problem plants.

Chartered Institute of Ecology and Environmental Management (CIEEM) President Max Wade CEcol CEnv FCIEEM gave evidence last month in Parliament on Japanese knotweed. Representatives from Swansea University, Swansea Council, Japanese Knotweed Ltd, the Royal Institution of Chartered Surveyors (RICS), Environment Agency, Property Care Association and UK Finance were also on the panel.  

 The key outcomes were: 

  • There has been a lack of empirical evidence on Japanese knotweed historically
  • Recent research has found that Japanese knotweed is no more damaging to buildings than other ‘problem’ plant species e.g. bamboo and buddleia
  • The 7m impact zone should be reviewed, given that this research found that the rhizome extension rarely extends more than 4m  
  • Distance to the property and/or boundary, environmental conditions such as soil type condition and other factors such as risk of spread need to be considered
  • There is a current over reliance on glyphosate in treatment, research is being undertaken to identify more effective treatment methods 
  • Further empirical research and collaboration between agencies is required
  • The Royal Institute of Chartered Surveyors will review their guidelines in 2019

For more information see the CIEEM website


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