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Fallopia Japonica, known as Japanese knotweed, is a highly invasive plant species that has become a significant problem in many parts of Britain. The plant, which is native to Japan, was brought to the United Kingdom in the 19th century by the Victorians as an ornamental garden plant. The plant was widely distributed and planted before its invasive power was known. However, it quickly spread and became a serious problem due to its aggressive growth and ability to outcompete native vegetation and foliage. Japanese knotweed can be found throughout Britain and areas with high concentration of the plant can be found in Bristol, Nottingham, Rotherham, and Glasgow.

The knotweed at its most aggressive can break through tarmac or concrete and can grow up to 20cm per day. It also has a deep root system that can grow up to 3m deep and has potential to cause damage to the foundations of properties, block underground drains and damage brickwork. There is a risk that if the plant is not properly removed, tiny fragments of the stem or roots can float to other areas of the property and/or neighbouring properties and the plant will grow again.

How do you remove Japanese knotweed?

Depending on the removal method chosen, the cost of removing Japanese knotweed can range from £950 for domestic herbicide treatment on a smaller infant plant, to £20,000 for excavation, relocation, and ongoing treatment on a larger more mature plant. It is reported that Japanese knotweed in Britain causes £170 million of damage per year.

How does Japanese knotweed affect my sale or purchase?

The presence of Japanese knotweed on a property can have a significant impact on the conveyancing process. Typically, when buying or selling a property, a buyer will carry out a survey of the property to identify any potential issues. If Japanese knotweed is present anywhere on the property, or within close proximity of the property boundaries, it will likely be flagged as a potential issue.

The presence of Japanese knotweed can make securing a mortgage on a property challenging, as many lenders will not provide a mortgage on a property that is affected by the plant, viewing properties with knotweed as a higher risk mortgage investment due to; the potential damage the knotweed can cause to properties, the cost of removing the knotweed and the risk that the plant can lie dormant until the ground is disturbed – when building an extension for instance. Mortgage lenders will assess the suitability of the property for a mortgage based on their own policies on Japanese knotweed, with some lenders having more stringent restrictions than others.

In addition, the presence of Japanese knotweed can reduce the value of a property. This is because the high cost of removing the knotweed will typically be passed on to the buyer, and when selling a property where Japanese knotweed has previously been present the seller may be asked to provide guarantees of professionally completed works to remove the knotweed.

Does home insurance cover me for the potential impacts of Japanese knotweed?

The presence of the plant can make it difficult to obtain effective insurance for a property as most home insurance policies do not cover Japanese knotweed and will exclude damage caused by the knotweed from its policies. Although the presence of the knotweed will not necessarily increase home insurance premiums, individuals will need to foot the cost of removing the plant and any damage it has caused to the property due the policies not covering Japanese knotweed. It is possible to take out indemnity insurance if Japanese knotweed has not been discovered on a property, which can protect property owners against the cost involved with possible infestations in the future, including the cost of specialist surveys and effective removal of the plant.

For these reasons, it is essential that property owners take steps to identify and remove Japanese knotweed from their property. This can include hiring a professional to carry out a survey of the property, and if identified, to remove the plant. Please follow the link below for information on how to identify Japanese knotweed:

If I do not remove the plant, am I breaking the law?

It’s important to note that there are laws in place that require property owners to take action to prevent the spread of Japanese knotweed, and the damage it can cause. It is an offence to fail to reasonably address Japanese knotweed on your property, under the Anti-Social Behaviour, Crime and Policing Act 2014. This means that property owners can be held liable if the plant causes damage or spreads from their property to a neighbouring property. Please follow the link below which explains what can be done to stop the spread of Japanese knotweed:

Court Rulings relating to Japanese knotweed

Recently, there have been significant case law rulings in relation to Japanese knotweed. In February 2023, the court of appeal ruled that a homeowner could recover damages for the loss of value of their property from the knotweed due to the stigma attached to the affected property, even after effective removal of the plant.

In the case of Davies v Bridgend County Borough Council [2023] EWCA Civ 80, it was acknowledged that even if knotweed has been treated and removed, some roots can still be in the ground and therefore the stigma can remain as perspective buyers may anticipate the damage Japanese knotweed can cause, effectively lowering the property’s value in the marketplace.  Mr Davies was awarded £4,900 from Bridgend County Borough Council in South Wales in this judgment and claimed he was unable to carry out landscaping or put up a shed on his property due to the previous presence of the plant. Another key finding from this case, is that although the knotweed had spread to Mr Davies’ property before the Defendant could have reasonably known about the knotweed, the Defendant had breached their duties and was liable to pay in relation to the reduced value of Mr Davies’ property. The Defendant has been given permission to appeal the outcome to the Supreme Court, so we await to hear when this may take place and any potential findings.

In conclusion, Japanese knotweed is a noteworthy problem in many parts of Britain, and it can have a significant impact on the conveyancing process specifically due to the knock-on impact its presence has on the buyer’s ability to secure a mortgage and the costly requirement to remove the plant. It is advisable that property owners take steps to identify and remove the plant from their property, and to prevent it from spreading to neighbouring properties. To ensure that the property is free from the knotweed and to prevent financial and legal issues.

This article is for general information only and does not constitute legal advice.

If you are a business or an individual looking for specific advice on your legal rights and obligations in respect of Japanese knotweed, for instance when selling your property, finding that Japanese knotweed is spreading onto your property, or finding that Japanese Knotweed is present at a property which you have recently purchased, then please do not hesitate to get in touch. You can contact CTT Law Ltd on 01926 563 670, and a member of the team will be happy to assist you.