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Japanese Knotweed - a Guide for Homeowners, Sellers and Buyers

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UK property owners’ land and homes are being infected by the rapidly growing species Japanese knotweed, which can damage building’s foundations and floors, as well as growing through walls and fences.

Initially introduced to the UK in the 19th century from Asia to stabilise railway tracks and improve the appearance of railway embankments, Japanese knotweed has been a growing problem across the country in recent years.

Cases of Japanese knotweed have increased by 28% in five years according to a new survey, with a definite 29,000 confirmed outbreaks of the weed and a further 19,702 unconfirmed outbreaks as reported in the Ends Report.

Data from South Yorkshire, Hampshire and West Sussex suggests these areas are seeing the fastest rise in cases.

Eradication of the weed would seem like the correct solution. Yet, the government rejected the idea when it was proposed in parliament due to how expensive it would be to complete, costing at least a staggering £1.5 billion. 

When selling a property, it’s important that any property flaws are publicly made known to potential buyers. Although it might not be well known that this particular species of plant must be declared when selling a home, it is the homeowner’s obligation to state the existence of Japanese knotweed on their property due to the concerns about the damage it can cause.

Similarly, when purchasing a new home, needing to know about the existence of Japanese knotweed on the property is a must.

With so many homeowners, sellers and buyers being unaware of the dangers posed by Japanese knotweed and the legal obligation to disclose its presence, it is important to make sure you are up to speed, especially if you live in one of the areas most affected.

What is Japanese knotweed?

Japanese knotweed is a non-native species in the UK. It originates from Eastern Asia, Japan, China, Korea, and Taiwan, usually found on the side of volcanoes. The species itself is fast-growing and invasive.

During winter months, the stems stand dried, and the plant’s rootstalks (or ‘rhizomes’) are hidden in the ground. It is these rhizomes which cause the damage to property foundations.

Once summer comes, the plants grow again into dense stems which commonly stand around 7ft tall.

Once fully grown, the appearance of Japanese knotweed is of solid stems coloured green with purple flecks. They have leaves that are either shovel or heart-shaped, with their stems pattern being zig-zagged. Towards late summer and early autumn, they produce a white flower.

Why is Japanese knotweed a problem for homeowners?

Japanese knotweed can be damaging to properties if not controlled or entirely removed. The rapid growth has been known to damage building foundations, breakthrough concrete floors and kill off other species of plants.

As Japanese knotweed has been recognised in the UK as an invasive plant, it can have an impact on the value of a property or the possibility of obtaining a mortgage on an affected property.

The devaluation caused by the presence of Japanese knotweed is usually around 5-15%, and it is generally determined by the amount of Japanese knotweed and the proximity of it to a habitable building. However, some properties have been completed devalued due to the severity of the knotweed invasion.

Where is Japanese knotweed commonly found in the UK?

Japanese knotweed has alas made its way across the UK since the 19th century. With cases being reported throughout the country. The most commonly found places to have Japanese knotweed currently are South West Wales, Bristol, Manchester and London, with many areas cases continuing to rise. 

Is it a crime to have Japanese knotweed on your property?

If your property is affected by the Japanese knotweed species, you are not breaking the law by not removing the weed.

However, the Anti-social Behaviour, Crime and Policing Act 2014 does state that if the growth of Japanese knotweed is not under control and affecting the neighbouring area, the property owners could be liable to prosecution.

Do you have to tell buyers there is Japanese knotweed on your property?

When selling a home, if you are aware of Japanese knotweed being on the property, you are required to disclosure it to the potential buyers through a TA6 form (Property information used for conveyancing); otherwise, you are misrepresenting the land and could in the future be at risk of being sued.

What can you do if you have brought a property with Japanese knotweed?

If you have bought a property with Japanese knotweed, it is essential that you are prepared to stop the spread of it from your property; otherwise, you could be liable.

The GOV.UK website lists ways in which you can prevent the further spread of Japanese knotweed, these include:

  • Chemical sprays
  • Bury the waste – this must be at least 5 metres deep and covered with a root barrier membrane layer
  • Burning it

It is not recommended to attempt to handle the removal of Japanese knotweed yourself. If it is done incorrectly and spread into the wild, you could be liable for prosecution. To avoid this, it would be wise to seek professional help for the removal.

If you have been misled about the existence of Japanese knotweed on a property you have purchased, our London property dispute solicitors can help you to make a claim. 

How HPLP can help with Japanese knotweed problems for homeowners, sellers, and buyers

If your home is affected by Japanese knotweed or you want to check a property for the existence, you need specialist legal advice to help assist you.

Our residential conveyancing lawyers have dealt with many Japanese knotweed cases. We can provide you with the correct legal assistance that you need.