3 things you need to know about Japanese Knotweed


Have you experienced an invasion of Japanese Knotweed? Not only is this invasive plant difficult to control, but it can also affect the value of your property and even surrounding property if left to spread. We’ve pulled together a need-to-know guide, so you can tackle this bugbear problem head on. 

What does it look like?


Japanese Knotweed is often seen as a beautiful plant with its rich green leaves and bright red stems. It is in fact its appearance which first landed it here in the UK from Japan. But, it is in fact a perennial plant which has been causing havoc for homeowners ever since. 

This type of plant is relentless, it will return each year and its appearance can also change drastically depending upon the season. So, what do you need to be on the look-out for? 

  • Spring; is the season when it starts growing, and rapidly too! New shoots will appear, bearing a red to purple colour.
  • Summer; the plant will be fully grown reaching a maximum height of 2 to 3 metres in a single season. The deep green leaves will flourish and appear “heart” shaped.
  • Autumn; clusters of cream and white flowers will appear on the plant.
  • Winter; the leaves will fall and the canes die, turning brown, but the canes will remain standing.

It can cause several issues for homeowners and developers 


Japanese Knotweed can cause several issues for homeowners and property developers. Recent research indicates that this prolific plant has wiped a staggering £20bn off the total value of the UK property market. The issues the Japanese plant causes are varying:

  • It’s estimated that 850,000 to 900,000 houses are affected by the plant in the UK alone 
  • It’s widely reported that it can knock up to 10% off a property’s value 
  • You will not be able to obtain a mortgage or re-mortgage a property where Japanese Knotweed is present, unless a survey and management plan in place, with the first treatment complete, for its removal by a competent contractor.
  • It’s an invasive plant that can be difficult to control 
  • Its roots can spread up to 7 metres from the plant. It’s also surprisingly strong, the roots have ben know to break through tarmac and concrete and to even cause damage to drains and concrete foundations  
  • If Knotweed spreads from your property onto a neighbour’s and it is deemed that you have caused a detriment to their enjoyment or property this can lead to compensation claims.

Knotweed is considered a “controlled waste” under Section 34 of the Environmental Protection Act 1990.


Not only can Japanese Knotweed cause serious damage to your property, but it can also have serious legal implications for homeowners too! If you’re found to have left the plant to spread, it could lead to a maximum five year imprisonment or fines of £50,000 upwards should the case be taken to the Crown Court. You can protect yourself by: 

  • If the knotweed is on your property you are responsible! 
  • If left to spread, it can lead to potential prosecution, fines and compensation claims being made against you.
  • Dispose of the Knotweed correctly. You will require a licensed carrier – ask them for proof of correct disposal.

How can we help? 


If you suspect you have Japanese Knotweed, but are not sure, get in touch with our team. As RICS Registered Valuers we are often the first on site for clients, developers and lenders therefore it is important that we can quickly and effectively identify this invasive plant and provide you advice on what to do next. Contact us with your enquiry. 

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