Japanese Knotweed is a contentious plant that can depreciate the value of a property and cause conflict between neighbour’s. The invasive plant is known for spreading quickly and for monopolising gardens. Knotweed grows in large patches that can quickly push out any other competing plant life. Thankfully, Japanese Knotweed is easy to identify, so homeowners can waste no time in getting a treatment plan in place to get rid of the plant.

Although there is plenty of discussion regarding how Japanese Knotweed spreads, and what to do if you’ve bought a property with Knotweed, how this plant first got to the UK is not usually discussed. Japanese Knotweed’s history is an interesting one and can help give insight into why it has flourished so well in the UK and what lessons can be learned when dealing with invasive plants in the future.

Where is Japanese Knotweed originally from?

Japanese Knotweed is originally from Japan and is also native to China and Korea. The plant is one of many species of plants that have been discovered to be growing on the side of volcanoes. In its native land, Japanese Knotweed can reproduce naturally and also benefits from a prodigious underground system of rhizomes. In its native environment, Knotweed is kept in check by natural predators in the form of fungi and insects, not to mention other plants and an environment that can be much more hostile than the United Kingdom.

The plant was originally discovered by Dutch naturalist Maarten Houttuyn in the 18th-Century, he named it Reynoutria japonica, a name which it still goes by today. Unfortunately, the records of this original discovery were lost for some time, so when more European botanists started exploring Japan some 150 years later, the plant was rediscovered and given a new name by a Bavarian botanist, Phillip von Siebold. Siebold and his partner Zuccarini, named the plant Polygonum cuspidatum. It wasn’t until the turn of the 20th century that a Japanese botanist by the name of Makino, discovered that Houttuyn and Siebold’s plant were one and the same.

Who brought Japanese Knotweed to the UK?

Philip von Siebold brought Japanese Knotweed to the UK in 1850, unaware of the impact that it would go on to have on the environment. At the time, botany and the cultivation of plants was a popular interest of the upper classes. Botanist like Siebold would be able to fund their research trips by sending their discoveries back to nurseries on the European continent, where they would then be cultivated and sold onto commercial nurseries or botanical gardens around the world.

Why was Japanese Knotweed imported to the UK?

Japanese Knotweed was imported to the UK for commercial sale and botanical cultivation. Over the time that he spent in Japan, Siebold collected and recorded over 1,000 different plants, often choosing to plant them in the garden behind his research base on Dejima, an artificial island near Nagasaki. Periodically, Siebold would box up a number of samples and send them back to his home in the Netherland. From their new home in Leiden, these plants would be carefully grown and the packaged up for botanical gardens in Belgium and Britain, with an unmarked box containing Japanese Knotweed arriving at London’s Kew Gardens in 1850.

Kew Gardens often relied on these boxes of new plants to keep their own collections diverse and interesting for visitors. After discovering how quickly the plant could grow in Britain, the horticulturists there recognised Japanese Knotweed as a plant that could be easily cultivated and sold on to budding gardeners. Soon the plant was being distributed to garden nurseries around the country and then shared in cuttings by enthusiastic gardeners. In addition to being intentionally spread by people, the plant also began to spread by its own means, populating river banks and finding new routes to the rest of the country along roads and newly built railway lines.

Where does Japanese Knotweed grow in UK?

Japanese Knotweed now grows in almost every area of the UK. The plant was given free rein to spread throughout the country for over a hundred years before being recognised as invasive by the government. By the time Japanese Knotweed was identified as an invasive threat in 1981, it had already been spread by gardeners, dug up and transported by urban development projects and even used to stabilise soil on the sides of railway lines.

The plant is frequently found growing alongside public watercourses such as canals, as well as near railway lines, motorways and public footpaths. Japanese Knotweed thrives in most conditions in the UK and is often found growing on land that has been abandoned or left unattended. For this reason, large infestations can often be discovered in overgrown back gardens, or on abandoned industrial sites.

How common is Japanese Knotweed in the UK?

Japanese Knotweed is a very common sight in the UK. Since the government has made the spread of Japanese Knotweed a more pressing concern, efforts have been made to track where it has been growing throughout the country. Using these statistics, it’s been possible to recognise the areas of the country that have been most affected by Japanese Knotweed. Bolton, Bristol, Conway, Rotherham and Nottingham are areas in the UK that have been affected the most, however exact numbers are difficult to assess

What do I do if I find Japanese Knotweed?

If you find Japanese Knotweed it’s important to ascertain where the plant has come from and to what extent the plant affects your property. You may want to consider contacting a Japanese Knotweed specialist to make a positive identification before you move forward with talking to any neighbour’s who might also have the plant on their land. Ignoring the infestation is not advised, as the plant can quickly multiply, leading to a larger problem to deal with and potentially more costs, if you find that it’s not possible to claim compensation for the cost of treatment.

If you think you’ve found Japanese Knotweed and would like some advice on what to do next, then you can contact us by calling freephone 03335 777 888 or send us a message using the contact form on this page.

Polygonum bidwelliae

Japanese Knotweed can have a negative impact on the value of your property, not to mention causing conflict between neighbour’s and causing stress in your day-to-day life. Discovering a Japanese Knotweed infestation can also lead to some very expensive costs, which many might wish to alleviate by relying on their home insurance. Unfortunately, making a claim on your home insurance after discovering Japanese Knotweed is not always straightforward, or even possible, in some cases.

Does house insurance cover Japanese Knotweed?

Most house insurance policies will not cover losses incurred as a result of Japanese Knotweed. However, there are some exceptions to this rule, such as if the plant has caused subsidence, or if it has spread from a neighbouring property. Having Japanese Knotweed on your land also might prompt other questions, such as how it could affect your premiums and if your insurance might cover the legal costs of a Japanese Knotweed claim made against you.

Will my insurance provider pay for treatment of Japanese Knotweed?

Home insurance providers will not pay for treatment of Japanese Knotweed. If you have discovered the plant on your land and can prove that it has either entered from a neighbouring property, or the seller has lied about the Japanese Knotweed, then you may be able to claim compensation to cover the cost of damages.

Am I covered for damage caused by Japanese Knotweed?

Standard house insurance policies do not typically cover the costs related to repairing the damages caused by Japanese Knotweed growing on your land. However, in the case that the Japanese Knotweed has caused structural damage to your home, like subsidence, you may be able to claim for damages. Although, successful claims are only likely to be made when you can prove that you have taken reasonable steps to eradicate the Japanese Knotweed before the subsidence took place.

This is a good example of how important it is to not delay dealing with a Japanese Knotweed infestation, doing so can result in serious repercussions such as the above, as well as the potential legal implications of allowing the plant to spread to a neighbouring property.

Will my insurance cover Japanese Knotweed from a neighbouring property?

Depending on your policy, your insurance may cover the cost of repairing damage caused by Japanese Knotweed entering from a neighbouring property. In this circumstance, your insurers may seek to pursue your neighbour’s for the costs related to the damage to the property.

Will my insurance cover legal expenses if my neighbour claims for Japanese Knotweed damages?

Your insurance policy might cover the cost of legal expenses in the event that your neighbour attempts to claim for compensation for damages caused by Japanese Knotweed entering your land.

It is against the law to allow Japanese Knotweed to spread from your land into a neighbouring property, regardless of if it’s publicly or privately owned. If your neighbour can prove that you have allowed the plant to spread into their land then you could be found liable for the loss of value of the property, as well as any treatment costs that the infestation might have incurred.

In most cases, you are able to add-on legal expenses insurance on to your standard home insurance policy. You may wish to assess the fine print in your current policy if you’re worried that you might not be covered for this eventuality.

Do I need to inform my insurance provider that I have Japanese Knotweed?

You do not need to inform your insurance provider about the Japanese Knotweed on your land. In the event that you find Japanese Knotweed on your property, you should do as much as you can to prevent it further spreading and causing damage to your property. If you fail to do this, your insurance provider may decline a future claim for damage caused by subsidence, on the grounds that you have acted negligently in not treating the problem sooner. In the eventuality that you are directly asked about the presence of Japanese Knotweed on your property by your insurance provider, you must be honest with them.

Can I get house insurance if I have Japanese Knotweed?

You can still get house insurance if you have Japanese Knotweed on your land. As standard house insurance policies do not tend to cover the costs of removing Japanese Knotweed or the damages caused by the plant to the property insurers are not likely to take this into account. However, in the case that you are directly asked about having Japanese Knotweed, it’s recommended to answer honestly and openly.

Will having Japanese Knotweed affect my house insurance premiums?

Having Japanese Knotweed shouldn’t affect your home insurance premium. Most standard house insurance policies will not cover the removal of Japanese Knotweed, or repairs to anything damaged by it. As such, your discovery of the plant, whether or not it has originated on your land, should not affect your premiums.

However, in the case that you plan on claiming for damages related to subsidence caused by Japanese Knotweed, you will likely find that your premium will increase. Don’t forget that, in the event that you do make a successful claim, you will also have to pay the excess laid out in your policy. Claiming for subsidence cover can also negatively impact your ability to get insurance cover for subsidence in the future, as your home will have been flagged as high-risk by the insurance companies.

What insurance do I need to cover me against Japanese Knotweed?

Since 2015, it has been possible to buy specific Japanese Knotweed insurance which covers the cost of removing the plant, and the potential costs related to claims against you, as a result of the Knotweed spreading to a neighbouring property.

A Japanese Knotweed indemnity insurance policy will cover the costs of treating and removing the infestation, in addition to preventative insurance-backed measures to stop the plant from returning. The policy should also cover the cost of a Japanese Knotweed survey, as well as any reparation costs in relation to damages to the property and legal expenses paid for as a result of claims made against you. These policies were created with the intention of easing the conveyancing process, in cases where homes have been affected by the plant.

Japanese Knotweed insurance policies are usually for 10 years, with the limit of indemnity being based on your property’s market value, offering valuable protection to both you and your mortgage lender. It should be noted that these Japanese Knotweed indemnity policies are only available for residential properties where the presence of the plant is not known, or if treatment has taken place to the satisfaction of the mortgage lender.

Too little, too late?

Unfortunately, Japanese Knotweed indemnity policies, such as the above, have not been advertised to their full extent, so for many, the discovery of them will be a case of too little, too late. If you’ve found Japanese Knotweed on your land, and have found that your insurance does not cover the costs of repairing damages or removal, then you may be able to seek compensation against the seller of the property or even the persons or organisations who have allowed the plant to spread to your land.

Get in touch with us by sending a message using the contact form, or calling us freephone 03335 777 888

espite Japanese Knotweed having made a significant impact on the property industry in the last decade, there are still cases where surveyors miss this invasive plant whilst conducting mortgage evaluations, Home Buyer Reports and RICS Building Surveys. In many of these scenarios, buyers are left in a precarious place, having already invested hundreds of pounds into the home buying process and often reaching the point of no return before making the discovery of an infestation.

The following guidance is intended for those who have discovered that their surveyor has missed Japanese Knotweed:

Do surveyors look for Japanese Knotweed?

RICS qualified surveyors are trained to look for large masses of vegetation that could signify an invasive plant infestation. A professional surveyor is expected to keep up to date with ongoing development in their industry, which includes the common risk factors that could point to a Japanese Knotweed problem. The RICS have laid out an assessment framework in their resource materials for Japanese Knotweed which includes pre-inspection checks of the local area, an inspection of the property itself and even inspection of neighbouring communal areas.

The RICS notes pertaining to Japanese Knotweed lay out four distinct categories that property surveyors can use to inform their process. It’s important to note that each of these categories refers to the Japanese Knotweed being within 7 metres of either habitable spaces, buildings or boundaries. This ‘7-metre rule’ is based on the assumption that Japanese Knotweed has the capacity to grow up to 7 metres underground from the point that it can be spotted on the surface. This rule has come under scrutiny by the government who have suggested that it has been misused within the property industry, however, it has yet to be replaced by the RICS.

The four categories are ordered here in descending order from most severe to the least:

4: “Japanese Knotweed is within 7 metres of a habitable space, conservatory and/or garage, either within the boundaries of this property or in a neighbouring property or space; and/or Japanese Knotweed is causing serious damage to outbuildings, associated structures, drains, paths, boundary walls and fences and so on. Further investigations by an appropriately qualified and/or experienced person are required.”

3: “Although Japanese Knotweed is present within the boundaries of the property, it is more than 7 metres from a habitable space, conservatory, and/or garage. If there is damage to outbuildings, associated structures, paths and boundary walls and fences, it is minor. Further investigations by an appropriately qualified and/or experienced person are required.”

2: “Japanese Knotweed was not seen within the boundaries of this property, but it was seen on a neighbouring property or land. Here, it was within 7 metres of the boundary, but more than 7 metres away from habitable spaces, conservatory and/or garage of the subject property.”

1: “Japanese Knotweed was not seen on this property, but it can be seen on a neighbouring property or land where it was more than 7 metres.”

In the case where the surveyor deems the infestation to be of a category 3 or 4, then further investigations should be undertaken by an ‘appropriately qualified and/or experienced person’ in order to create a ‘management plan’. In the case where the infestation is classed as a category 1 or 2, the surveyor will decide if further investigations are warranted, depending on their client’s requirements and on their own professional judgment.

Should an RICS survey pick up the presence of Japanese Knotweed?

Whether or not a particular survey will identify Japanese Knotweed will depend on the type of survey that has been commissioned, the scale of the potential infestation, the professionalism of the surveyor and also the extent to which the owner of the property has attempted to conceal the plant.

Not all surveys are created equal. The RICS has a few different types of surveys which cover a range of budgets and scenarios. The cheapest of these is the RICS Condition Report, which costs around £250 and is intended to provide basic information regarding potential legal issues and any urgent problems that the property faces. In the RICS’ words, the visual inspection of the grounds is a ‘relatively cursory’ part of the process, however in cases where the surveyor is aware that there is a greater risk of Japanese Knotweed then this may require ‘particular attention’ on the part of the surveyor. Whilst the RICS materials do say that a client should purchase a Home Buyer Report or building survey if they wish to have ‘greater assurance’, this does not excuse a surveyor from completely missing Japanese Knotweed in their survey.

Should a mortgage valuation pick up Japanese Knotweed?

A mortgage valuation is not always guaranteed to pick up the presence of Japanese Knotweed. A mortgage valuation survey is paid for by a mortgage lender or bank in order to verify that the amount of money that they’re planning on lending is in accordance with the value of the property in question. A valuation is intended to satisfy the mortgage lender, as such, it will not single out any structural issues, or repairs that will need addressing before a purchase is made. Although the prospective buyer is usually expected to pay for the valuation, a surveyor might not focus their attention on the land surrounding the property.

How can a surveyor miss Japanese Knotweed?

Surveyors can miss Japanese Knotweed on a property for a number of reasons, not all of which suggest that they have acted negligently. Homeowners can often act fraudulently when attempting to sell a property infested with Japanese Knotweed, relying on cheap tricks to hide their infestation in order to push the sale through expediently. A property owner could choose to conceal the Japanese Knotweed by burying shoots in the spring with wood chips or topsoil. They might also choose to hack away any evidence of the plant above the surface and fly-tip the evidence.

DIY attempts at treating Japanese Knotweed can lead to deformed or sparse growth which may lead surveyors to miss the infestation altogether, or mistakenly identify it as another plant. Similarly, if the homeowner has paid for a professional removal service then the Japanese Knotweed might have entered into a dormant phase, where it might remain below the surface for years – completely undetectable to anyone.

In cases where property developers have built on land with Japanese Knotweed, the infestation might have been dispersed into the earth that your home has been built on. As Knotweed rhizomes can grow from a thumb-size piece into a full-size plant given enough time, a surveyor could easily miss the plant if it is still growing underneath the ground.

What happens if a surveyor missed Japanese Knotweed growing on a property you wish to buy?

If a surveyor missed the presence of Japanese Knotweed on a house before a purchase is made then the prospective buyer will be unable to rely on legal action to claim back any expenses that might have been accrued leading up to the discovery. Although the potential buyer might have already invested money in seeking a valuation and surveying the property, not to mention spending resources setting up the sale of their own home, unless a contract has been signed, they won’t be able to claim these expenses back from the negligent property surveyor.

What if you buy a house and then discover that the surveyor missed Japanese Knotweed on the land?

The discovery of Japanese Knotweed on a property can lead to the home being devalued by as much as 5% and can sometimes result in a mortgage lender or bank refusing to lend. A surveyor missing Japanese Knotweed can lead to sales falling through and thousands of pounds being wasted. If a Japanese Knotweed infestation is discovered on a property after a Home Evaluation Report or RICS Home Buyer Survey has said otherwise then the buyer may be able to bring legal action against the surveyor for professional negligence.

Can I sue my surveyor for missing Japanese Knotweed?

It is possible to sue a surveyor for missing Japanese Knotweed, in the event that the sale has of the house has gone through and it can be proved that the surveyor has acted negligently. Courts or tribunals will refer to the resources supplied by the RICS in order to determine whether or not a surveyor has acted negligently in missing Japanese Knotweed. In assessing each case attention will be paid to the lengths that the surveyor went to survey the property, the context surrounding the property, whether or not there’s Japanese Knotweed in neighbouring properties and any notes or recommendations that the surveyor might have made at the time of the survey.

Do surveyors have a duty of care to potential buyers?

According to the RICS Rules of Conduct, all members are required to carry out their work with ‘due skill, care and diligence and with proper regard for the technical standards expected of them’. , In addition to upholding the professional standards expected of them, all surveyors are required to maintain their professional competence by staying up to date with developments in their industry. Surveyors have a duty of care to both the lender and the homebuyer, regardless of if the owner has attempted to hide the infestation. Whether or not a surveyor is deemed to have properly performed their duty of care will depend on the context of the given case, including the type of survey that was ordered and the nature of the property.

Is there precedence for buyers suing surveyors for missing Japanese Knotweed?

In May 2019, Paul Ryb was awarded £50,000 after his RICS Level 3 Building Survey failed to pick up the Japanese Knotweed that was growing in the garden of his ground-floor London flat. Being partially sighted, Mr Ryb was relying completely on the professional opinion of the property surveyor who completely missed the plant on his survey of the building. The £50,000 awarded to Mr Ryb reflected the reduction in value of his £1.2 million home, in addition to the thousands of pounds that he was forced to spend on excavating the infestation. Mr Ryb was also awarded £90,000 to cover the costs of his legal fees.

Call us today on freephone 03335 777 888 or send us an enquiry using the contact form to see if we can help you with your Japanese Knotweed problem.

Japanese knotweed has been in the UK for more than a century, having been introduced by the Victorians in the 1800s. Native to China, Taiwan and Japan it was first brought to the UK as an ornamental plant for the garden. Fast forward in time and the plant is renowned now for being an invasive weed species. The growth of this plant is rigorous and it can spread as much as 2 metres in one growing season.

Because it’s growth is so aggressive and invasive, a number of Japanese knotweed laws were introduced in order to control its growth, and restrict its transportation. Homeowners need to be aware of Japanese knotweed legal responsibility and ensure they meet their Japanese knotweed legal obligation. It can quickly take over your garden and native species, as well as potentially reduce the price of your house.

What is the Law on Japanese Knotweed?

In the UK, the Japanese knotweed legal obligation is that it’s illegal to plant it or allow it to grow in the wild. It’s not, however, an offence to let it grow in your garden or on any land that you own. Your Japanese knotweed legal obligation also prohibits you from allowing it to escape and spread into a neighbour’s garden. It pays to be aware of your legal responsibilities if you want to avoid a costly day in court or problems with your local council or neighbours.

There are a number of laws that relate to the controlling of Japanese knotweed. They include:

Japanese Knotweed Anti-Social Behaviour Law

The negligent cultivation of Japanese knotweed came under the remit of the Anti-social Behaviour Crime and Policing Act 2014. Authorities, such as the local council and the police are able to issue Community Protection Notices if you are found to be negligently cultivating this invasive plant. The notice requires you to remove the species from your property and/or prevent its return. Failure to comply could result in a substantial fine.

EPA (Environmental Protection Act) 1990

This is the main legislation that relates to Japanese knotweed. The law gives details of methods to remove, transport, and dispose of the plant, considered to be “controlled waste”. As well as covering the plant itself, the legislation also covered plant materials or soil that could potentially be contaminated. Disposing of contaminated soil or plant material in an irresponsible way could result in a large fine.

Wildlife and Countryside Act 1981

This legislation supports the EPA of 1990 and relates to the growth of Japanese knotweed in the wild. Anyone found growing it in the wild faces a £5,000 fine, or a stay of 6 months in prison. You might think this is a little heavy but it does show how serious allowing the plant to grow unchecked is considered.

How to Recognise Japanese Knotweed

It’s quite easy to confuse Japanese knotweed with other common plants, but there are some very clear signs to look out for. During the summer, the green leaves are broad and shaped like a shield. The stems are reddish and hollow, much like bamboo. In the winter, the plant dies back, leaving stems that become brown and brittle.

What Can You Do if There is Japanese Knotweed in Neighbours Garden?

Your neighbour is under no Japanese knotweed legal obligation to remove it if they have it in their garden. If it starts to spread into your property, however, it is considered a private nuisance and you are legally permitted to take them to court. The best course of action is to talk to them about the problem and suggest they seek the help of a professional Japanese knotweed specialist. They might not be aware there is a problem, and by letting them know it is spreading to your garden, it gives them the opportunity to resolve the problem before it gets too costly.

There are plans to introduce predators and knotweed disease from Japan, but currently, the best course of action, if you’ve got it in your garden and want it removed, is to enlist the help of a professional Japanese knotweed specialist.

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