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What is Japanese Knotweed?

Japanese Knotweed (pictured above) is a form of non-native ‘alien’ species that was introduced to the United Kingdom in the nineteenth century as an ornamental plant. It is now the most invasive plant in the UK and spreads rapidly by its roots and stems, making it extremely difficult to eradicate from land. Japanese Knotweed can grow by up to an astonishing 10cm per day and its roots can extend to a depth of three metres meaning that, even if a small piece of root or stem is left in the ground, land can quickly become re-infested!

The rise and rise of Japanese Knotweed

Its roots grow so rapidly and aggressively that Japanese Knotweed is known for its ability to penetrate foundations, concrete and walls – causing considerable damage and costing substantial amounts to remove. It can also lie dormant for up to 20 years, especially after poor herbicide treatment and it has been estimated that over one percent of domestic properties in the UK are, or have been, affected, all of which could have several neighbouring properties that are also unknowingly infested. For perspective, the costs of eradicating Japanese Knotweed from the Olympic Park in Stratford, London are thought to have been approximately £70 million, whilst the Government estimates that the cost of totally eradicating it from the UK would exceed a staggering £2.6 billion.

Why is Japanese Knotweed a property issue?

Anybody dealing with property affected by Japanese Knotweed should be aware of the potential it can have due to:

  •  Its physical effect on the structure of buildings
  •  The costs of removing it from land
  •  The liabilities it can cause in relation to third parties
  •  Its impact of your ability to sell your property
  •  Its impact on your ability to obtain a mortgage

Whilst buyers are able to take out specialist insurance cover against the risks, its presence might affect the value of property. Any known presence should be reported to a lender immediately who may in turn consider their position and consider placing additional mortgage restrictions against a buyer.

Although the presence of Japanese Knotweed is covered in some standard property enquiries, it is rarely dealt with in environmental reports and a seller will usually ask a buyer to rely on its own searches and surveys.  If it is known that a property is contaminated with Japanese Knotweed, a buyer might seek a price reduction and/or an indemnity to protect themselves from claims from neighbours before agreeing to proceed.

Can having Japanese Knotweed be an offence?

Although it is not an offence to have Japanese Knotweed on your property and there is no general duty to control, remove or report its presence, it is an offence under the Wildlife and Countryside Act 1981 to plant it or cause it to grow in the wild (which can include a failure to take reasonable steps to control it) and can lead to penalties including:

  • A fine of up to £2,500 for individuals or £20,000 for companies; and
  • Imprisonment of up to two years.

Local authorities can also require the clearance of Japanese Knotweed on private land under s.215 of the Town and Country Planning Act 1990 if they view that the amenity of an area is adversely affected by it, with the penalties for failure to comply with a notice including:

  • A fine of up to £1,000
  • Liability to pay the local authority’s reasonable costs in removing the Japanese Knotweed

If Japanese Knotweed moves from one piece of private land to neighbouring private land, that neighbour may also seek remedies for private nuisance which can include:

  • Damages equating to the cost of treatment
  • Damaged equating to the reduction in value of the neighbours’ land (including property)
  • An injunction requiring the treatment of the Japanese Knotweed

What should I do about Japanese Knotweed on my land?

If you have Japanese Knotweed on your land, simply digging it out is not advised because, as stated above, unless treated professionally it is highly likely to return. Because it is so invasive, Japanese Knotweed is considered to be ‘controlled waste’ and must be disposed of in a controlled manner at a licensed landfill site – not simply in your green recycling bin! You should isolate the area affected and thoroughly clean all tools and equipment you have used before seeking expert help.

Japanese Knotweed – expert legal advice

Whether you are an individual or a business, if you have purchased or are selling a property affected by Japanese Knotweed, or are worried about Japanese Knotweed on neighbouring land, our team of Commercial and Residential Property experts are here to help.  Speak to a member of our team today using one of the telephone numbers below.