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How do I know if a property is affected with Japanese Knotweed? A New Heatmap may be the answer.

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Japanese knotweed has become well known in the UK as a nuisance plant, which can lead to structural damage due to its aggressive nature and ability to grow through materials such as concrete and tarmac.  Genni Cooper, Solicitor in our Fareham Residential Conveyancing team, explains here how to spot the plant, how to proceed with removing it and how a new website could help you identify the level of risk for your area. 

If you are purchasing a property, it is particularly important to know if the property is affected by Japanese Knotweed.  As this plant has a destructive nature, it can be costly to remove, usually requiring a specialist company to determine a management plan and to undertake the required treatment.  The presence of this plant can also cause difficulties if you are looking to obtain a mortgage, as a lender may not wish to lend at all or may require that treatment has begun/ been undertaken and a completion certificate and guarantee provided before they will further consider lending.

How can I check for Japanese Knotweed?

There is a new way to ascertain if the area in which you are purchasing is potentially infected by Japanese Knotweed by using a new ‘Heatmap’, which can be found by clicking here.  You can search via postcode which keeps the search simple.  This map will show you how many sightings have been in the area and will highlight the level of risk for the area via a scale of yellow to red colouring.  It is a quick way to determine particularly infected areas.  The map is interactive and can be updated with new sightings.  According to Environet, who have created the ‘Exposed: The Japanese Knotweed Heatmap’ the site is already well populated.  

What do I do if I find Japanese Knotweed at my property?

If you use the map and the area you are seeking to move to does show a likelihood of Japanese Knotweed, you may wish to arrange for a specialist survey which is specific to the property. This will confirm the presence of the plant and its extent. 

“Although the map is a useful and quick tool, in the cases where there are no sightings, this does not confirm that there is no Japanese Knotweed, as it may not have been reported,” explains Genni.  “We would still recommend having a specialist survey completed, as this map should only be used as a guide and should not be solely relied upon.”

Equally, if you already own your home or are perhaps looking to sell, you may wish to check if you are situated in a risky area.  If there are known sightings near your property, this could potentially deter buyers and you may wish to investigate further as to whether your property is infected and the possible management plans. 

As the map is interactive, you could report any instances of Japanese Knotweed that you are aware of for your own property or the surrounding areas. 

Signs of Japanese Knotweed

When looking for signs of this plant, check for the following characteristics such as:

  • Zig zag stems
  • Lush green colour leaves
  • Shield shaped leaves with a flat base
  • Bamboo style stems
  • Red tinged shoots
  • Found in dense clumps
  • In July it will sprout clusters of white flowers
  • Between September and November it will leave brown stems once the leaves have died back

It is worth remembering that even if Japanese Knotweed is not visible, it may still lay underground, especially in the winter months.  

If you have questions about Japanese Knotweed, or you are considering selling your property and are concerned about its presence, you can contact Genni Cooper or the Fareham Residential Conveyancing team on 01329 222099.


This is for information purposes only and is no substitute for, and should not be interpreted as, legal advice.  All content was correct at the time of publishing and we cannot be held responsible for any changes that may invalidate this article.