resource hub | Japanese knotweed – the decorative delinquent that needn’t cause panic

Japanese knotweed – the decorative delinquent that needn’t cause panic


Japanese knotweed (Fallopia japonica) was first introduced into Britain in the 1800’s.  It was sold primarily as an ornamental plant, and was even included in the Botanical Gardens at Kew.   


Today the plant is viewed very differently.  Following its spread into the wild, it is classed as a pest species under the Wildlife and Countryside Act 1981.


The plant has flourished across many parts of the UK as it has a remarkable growing ability.  It can grow up to 3m in height, leaves can be up to 14cm in length, and its creamy white flower tassles can grow to 15cm.  Underground, its deep penetrating stems (rhizomes) can extend up to 3m deep and 7m out from the parent plant.  It doesn’t produce seeds, instead new stems generate from even the smallest piece of the plant or rhizome. A perennial plant, it dies back in winter and resumes growth around April time.


Left unchecked, it can grow and spread rapidly.  It can exploit weaknesses in structures, both above and below ground, potentially posing a risk to property, driveways, underground drainage pipes etc. 


If you suspect you have Japanese knotweed on your property, don’t panic!  Japanese knotweed can be viewed as any other type of property problem in that it can be identified and treated, with minimal impact. 


Effective management and eradication of Japanese knotweed, indeed any invasive weed, is a job for the experts, so it is vitally important to seek professional advice.   


Specialists trained in the management and eradication of invasive weeds will in the first instance be able to confirm identification of the plant as Japanese knotweed, or other invasive weed (or not as the case may be).  Where an invasive weed problem is confirmed, they will then be able to:


  • Complete a thorough site assessment
  • Produce a report outlining a management plan, including a consideration of the options for control along with an explanation behind the recommendations and an estimate of costs
  • Offer an appropriate warranty for the work proposed, if relevant
  • Draw up a contract for agreement by all parties prior to beginning any work on a management plan


Some important “do’s and don’ts” to remember if you suspect Japanese knotweed is on your property:


DO take action and consult a professional as soon as you suspect Japanese knotweed as it can grow rapidly and then there will be more to deal with.


DON’T just dig up or cut the plant down and cover it up. The plant can regenerate from any small fragments this might create.  The composting process does not necessarily kill the plant and instead creates numerous small fragments of plant material which could exacerbate its spread. Causing the plant to spread beyond your property is an offence as it contravenes the Wildlife & Countryside Act 1981 (as amended).


Furthermore, as soon as the plant is cut down or dug up it is then classed as waste and in accordance with the Environmental Act 1990 would have to be taken by law to a licensed landfill site with the necessary facilities to dispose of it. 


DON’T contact the Environment Agency, SEPA, Natural Resources Wales or the Northern Ireland Environment Agency as they cannot provide advice on specific situations or recommend contractors. 


The majority of properties do not have Japanese knotweed growing on them.  But, if you suspect Japanese knotweed it is best to seek professional advice straight away from one of the many professionals based across the UK.


More information: Property Care Association website


Search for “Invasive Weed Controllers” via the TrustMark website.