Everything You Need to Know About Japanese Knotweed Surveys
If you suspect that you might have Japanese knotweed on your site, it is important that you get it properly identified by a professional who is qualified and or experienced in relevant areas. The best way to do this would be by booking a Japanese knotweed survey. However, before you book a Japanese knotweed survey, it could be beneficial to understand exactly what it is and how an invasive species survey of this nature would be carried out.
What is Japanese knotweed?
Also known as fallopia japonica, polygonum cuspidatum and reynoutria japonica, Japanese knotweed is a species of plant that grows and spreads quickly across primarily rural areas. It usually develops into tall, thick stems with branches that grow outwardly and large green leaves carrying white flowers.
During colder months of the year, it loses strength and moves to ground level, making it easier to manage and less invasive. However, across spring and summer, Japanese knotweed is typically tall – sometimes reaching heights above two metres – and susceptible to rapid growth across multiple surfaces.
Japanese knotweed history
Dating back to the 1700s, Japanese knotweed was originally discovered in Japan before being brought to Europe by German botanist Philipp von Siebold in the 1840s. After initially being praised for its beauty and used by farmers as animal feed, Japanese knotweed eventually featured in the Royal Botanical Gardens in Kew and Edinburgh.
It then began to be sold commercially, and the growing popularity led journalist William Robinson to encourage consumers to buy the plant in his book ‘The Wild Garden’. Meanwhile, it was described by John Wood in his book ‘Hardy Perennials and Old-Fashioned Garden Flowers’ as the ‘capital plant for the small town garden’. However, the perception of Japanese knotweed altered significantly in 1887 when gardeners realised that it was capable of spreading rapidly, extremely difficult to control and detrimental to the wellbeing of other plant life around it.
After being in circulation in the UK for over 100 years, Japanese knotweed presents a relentless form of plant life that can overwhelm large areas and hinder land development projects. Between its ability to spread across both rural and urban areas, and the difficulty to prevent the spread through being undetected via waterways and mistakenly distributed in contaminated soil that was used for construction, the presence of Japanese knotweed has become a widespread problem across the country.
Japanese knotweed in UK law
Due to the destructive nature of Japanese knotweed, it was listed in Schedule 9 of the Wildlife and Countryside Act 1981. Under these rules, it is a legal offence to plant Japanese knotweed in the wild, allow it to grow, or dump material that could be contaminated with traces of it. Likewise, it could be an offence if a landowner or homeowner allowed Japanese knotweed to spread from their land or property into neighbouring areas. However, this has not yet been tested in court.
Additionally, Japanese knotweed is also listed as a form of controlled waste under the Environmental Protection Act 1990. As such, it is an offence to possess, maintain or dispose of Japanese knotweed in a way that could potentially cause harm to human life or pollution to the environment. Instead, it should only be disposed of properly at licenced landfill sites.
What does Japanese knotweed do?
Japanese knotweed possesses properties that make it a troublesome plant in any area. It is both strong and capable of accelerated growth, allowing it to get into cracks, exploit weak points and grow within confined areas to cause significant harm to a property or plot of land.
Powerful enough to cause structure damage to property boundary walls and fences, brickwork, concrete, foundations, paving, tarmac, associated structures and almost any material it comes into contact with, there is practically no limit in terms of much an area could be affected by Japanese knotweed.
Why is Japanese knotweed bad?
Although it can be easy to dismiss the potential severity of Japanese knotweed, it is important to take it seriously. Due to the quick, robust and unforgiving nature of Japanese knotweed, catching it early could prevent potentially disastrous implications. Japanese knotweed is so relentless that it can grow in the most difficult of conditions including the sides of Japanese volcanos. The far more welcoming climate across the country makes it distinctly easier for it to grow in the UK.
You may be unaware of the dangers of leaving Japanese knotweed to grow, but there are countless horror stories. For instance, the devastating affect it has had on properties and even the presence of Japanese knotweed alone has led to the price of homes being significantly slashed. Likewise, property developers have seen planning permission applications refused due to invasive weeds of this nature being present on the site or causing existing significant damage to the area.
Is Japanese knotweed poisonous?
Despite the level of destruction Japanese knotweed poses, it is not poisonous and won’t cause harm if you come into direct contact with it. Often confused with giant hogweed, it is a common misconception that Japanese knotweed is harmful and could cause problems to humans internally or on the skin. In fact, it is so safe that it can technically be eaten raw or cooked. However, as it is illegal in the UK to possess Japanese knotweed, it would be advisable not to do this.
How to identify Japanese knotweed
Prior to booking a survey with an appropriately qualified and experienced ecologist, you will want to check that the plant you have found is in fact Japanese knotweed. It changes appearance multiple times over the course of the year and looks different at various stages in its lifespan, making the process of identifying Japanese knotweed difficult.
You may also fail to recognise Japanese knotweed based on its location. It could be that you find it visibly growing on paths, open areas of land, walls or anywhere within the plot of land or property boundary, for instance. However, it could be developing undetected and causing serious damage to an outbuilding associated with the property or plot of land. If it was growing in a conservatory and/or garage, for example, it could be far less likely to spot than in plain site. That said, it is possible to identify Japanese knotweed providing you know what you are looking for.
What does Japanese knotweed look like?
In the early stages, Japanese knotweed crown buds are distinctly bright pink and begin to sprout in the spring. You will then start to see thick, strong shoots that are green with red and purple sections, similar in appearance to asparagus. At this point, the leaves may appear rolled up and red or purple before turning green in the summer.
Between the spring and summer, the growth of Japanese knotweed will accelerate to as much as ten centimetres a day and the leaves will grow into large, bright green spears. Then, as the summer comes to a close, clusters of white flowers will develop on the leaves.
When the winter sets in, the leaves and flowers on Japanese knotweed die off, and the shoots decrease in length and turn dark, hard and lifeless. However, although Japanese knotweed may look dead at this point, it is very much alive and simply waiting to re-emerge when warmer weather returns in the following spring.
Is there Japanese knotweed in my area?
Currently the most destructive form of knotweed in the UK, Japanese knotweed has spread across the country. Due to this, it is fair to assume that it could feasibly appear at any location, and if you have any concern over the presence of this invasive plant, it would be advisable to book a Japanese knotweed survey.
Despite the nationwide presence and seemingly endless list of areas affected by Japanese knotweed, there are a few locations that have experienced a high number of cases. These include Birmingham, Blackpool, Brighton, Bristol, Cardiff, Leeds, Leicester, Liverpool, London, Manchester, Newcastle, Northampton, Nottingham, Peterborough, Plymouth, Sheffield, Southampton, Swansea and York.
Getting a mortgage with Japanese knotweed
For anyone looking to get a mortgage on a plot of land or property that has evidence of Japanese knotweed, the process can be far more difficult. Below, we explain whether getting a mortgage with Japanese knotweed presents a possibility of impacting land and property developers.
Can I get a mortgage with Japanese knotweed?
If a surveyor on behalf of a mortgage lender finds evidence of Japanese knotweed on a site or property and includes this in their report, it can seriously harm your chances of the loan provider giving you the funds you need.
Some lenders, including the likes of Barclays and Santander, require that you get a qualified and experienced professional in to eradicate the knotweed before they will consider making you a mortgage offer. Other mortgage lenders may allow for more flexibility with their guidelines. Nationwide and Clydesdale, for example, both simply request a report from a specialist surveyor before they would consider lending.
Mortgage lenders are apprehensive about lending for plots of land or properties that are infested with Japanese knotweed because it can seriously impact the ability to resell the plot of land or property in the future. Not only that, but in extreme circumstances, the roots of Japanese knotweed can even damage the foundations and draining systems of properties with severe infestations.
The cost of Japanese knotweed removal can vary significantly, with a simple herbicide treatment costing between £2,000 and £3,000 and a full disposal in a large area costing between £100,000 and £200,000. Even after paying a potentially hefty sum of money to have the knotweed removed, it could take several treatments over a number of seasons to entirely remove all traces.
Can you build on land with Japanese knotweed?
Technically, it is possible to build on land that has Japanese knotweed providing it isn’t a severe case, has been properly assessed and is in the process of undergoing an effective treatment plan. For example, four aces of Japanese knotweed was discovered during the process of building the Olympic Park for the 2021 Olympics in London. But through a significant investment of £70 million and a delay to the development, it was possible to remove it while continuing construction.
However, it isn’t always possible, and if a property or plot of land has a severe Japanese knotweed infestation, it would need to be dealt with before the development could begin. Within this situation, a survey from Japanese knotweed specialists would be required, and it could be used to determine whether the development could start before or even potentially during the treatment to eliminate the Japanese knotweed problem.
RICS on Japanese knotweed
In their paper ‘Japanese knotweed and residential property’, The Royal Institute of Chartered Surveyors (RICS) offer information on Japanese knotweed. The primary purpose of this paper was to help people who own plots of land or property that is infested with Japanese knotweed and prevent lenders from immediately denying mortgage applications due to the discovery of Japanese knotweed.
RICS Japanese knotweed categories
RICS’ ‘Japanese knotweed and residential property’ paper assists lenders with gauging the extremity of a Japanese knotweed problem on the specific property or plot of land. An effective way of doing this is through determining each case as falling into one of several predetermined risk categories that vary in severity. Depending on the category, further investigations by an appropriately trained and licenced ecologist in the form of a Japanese knotweed survey may or may not be needed.
Japanese knotweed risk categories:
- Category 1 Japanese knotweed – No presence of Japanese knotweed whatsoever.
- Category 2 Japanese knotweed – No presence of Japanese knotweed on the property or plot of land in question, but evidence of it seen on a neighbouring property or space of land more than seven metres away from the boundary.
- Category 3 Japanese knotweed – No presence of Japanese knotweed on the property or plot of land in question, but evidence of it within seven metres of the boundary and seven metres away from habitable spaces.
- Category 4 Japanese knotweed – Evidence of Japanese knotweed on the property or plot of land in question, but more than seven metres away from habitable spaces.
- Category 5 Japanese knotweed – Evidence of Japanese knotweed on the property or plot of land in question within seven metres of habitable spaces.
It is also important to bear in mind that habitable spaces refer to any section of the property that could be used for cooking, eating, living or sleeping such as a bedroom, kitchen, sitting room or conservatory, for example.
Based on these categories, the RICS would advise that a survey is carried out if the case of Japanese knotweed falls between category 4 and 5. For cases that fall between category 2 and 3, a Japanese knotweed survey may be required, but the decision will be based on the requirements of the client and professional opinion of the valuer.
How to report Japanese knotweed
If you spot what you think could be Japanese knotweed, it is possible to report it. By doing this, you can reduce the likelihood of it obstructing your land development project or damaging your property. Declaring Japanese knotweed is also important legally as, by reporting it correctly, you can abide by UK law and prevent it from spreading to other areas and causing further damage.
Do I have to report Japanese knotweed?
Under UK law, you do not have to report Japanese knotweed if you find evidence of it on land you own. However, it is advisable to report the presence of Japanese knotweed if you do not think that the local authorities are aware of it being present in the specific area or believe that it could cause serious damage to the local environment.
Who do I report Japanese knotweed to?
Whether you want to claim compensation for it spreading onto your property or simply want to ensure that they are aware of its presence in the area, most council websites have a section devoted to reporting specific issues such as Japanese knotweed.
You could also report Japanese knotweed to other authorities if required. For instance, if you identify it around trainlines, you should contact National Rail, and if you suspect that Japanese knotweed has been fly tipped, you should get in touch with the Environmental Agency.
Starting your Japanese knotweed survey
If you find evidence of what could be this invasive species on your property or land – or neighbouring property or land – it is important that you seek professional advice to determine whether Japanese knotweed is present. Further investigations by an appropriately qualified ecologist can then assess the severity of the infestation and provide effective next steps.
Who can survey Japanese knotweed?
At Arbtech, our team of experienced ecologists possess all of the necessary skills and qualifications to conduct Japanese knotweed surveys to the required standard. With over 15 years’ experience, we are established and knowledgeable about carrying out a wide range of invasive species surveys, and if you read our reviews, you will see for yourself how highly recommended we are as Japanese knotweed specialists, providing a quality service to our many clients within nationwide coverage across the UK.
How much does a Japanese knotweed survey cost?
As with many of our invasive species surveys, our Japanese knotweed survey is often site specific, with the cost varying based on the size of the plot of land and the magnitude of the development project. Due to this, it would be strongly recommended to get in touch and request a quote so we can provide you with Japanese knotweed survey costs that are accurate to your needs.
Japanese knotweed survey report
Once a Japanese knotweed survey is complete, the ecologist will put together an extensive report. In their Japanese knotweed survey report, they will offer thorough details about the purpose of the survey, key objectives, their results and findings, and effective recommendations that will ensure that the land development project goes ahead despite the presence of the plant. The report will then be sent to the client a few days after the survey is carried out.
Japanese knotweed management plan
Based on the results of the survey and the recommendations outlined in the report, a Knotweed Management Plan (KMP) can be developed. Japanese Knotweed Management plans will usually include a thorough strategy for how Japanese knotweed in the specific area will be dealt with, whether it is through the use of herbicide treatment visits, reducing or entirely removing traces of the plant or simply performing inspections to monitor growth.
Most mortgage lenders demand evidence that a KMP is in place. Likewise, the Environmental Agency state that a KMP must be created as soon as Japanese knotweed is found on a plot of land that is being used as part of a development project.
Booking a Japanese knotweed survey
When it comes to booking a Japanese knotweed survey with Arbtech, the process couldn’t be simpler. All you need to do is call us on 0808 169 4356 or fill in the quote form by clicking ‘Get Your Free Quote’ below.
After you have given us your details and specific information about the size of your plot and circumstances of your Japanese knotweed infestation, one of our team will give you a free quote, answer any questions you have and explain everything you need to know about using our services. Once a survey is booked, our Japanese knotweed specialists will come to your site and conduct a thorough risk assessment before providing you with a completed report outlining discovered traces of the invasive species and the potential level of destruction the knotweed presents, as well as effective measures for reversing the damage and eradicating all traces.