Japanese knotweed, you may have heard of it and if you’re reading this you certainly must be curious about it. there is no need to have it tie you in knots.
Japanese knotweed is thought to be present in nearly every 10 sq km of the UK. Approximately 4 – 5% of homes are affected either directly or indirectly. It can grow directly through asphalt and into drains, resulting in costly repairs.
The plant is difficult to kill and requires professional treatment over two to three years. DIY methods such as covering to deny sunlight, mowing, burning or treating with over the counter weed killer, simply won’t work and will make it worse
We’ve tried to cover a variety of items on this page to ensure it’s up to date, informative and you can find what you are looking for. Below you will find content to what you can expect. If you ever find out we recommend you get expert advice, if you are thinking of selling a property and you are having problems with knotweed we would be happy to talk to you about your options, why not give us a call for a no-obligation chat and see what options you have for selling a house with Japanese knotweed, we’re one of the UK’s top cash buyers so we’ve seen everything!
knotweed has been reported and see if your postcode is near a hot spot. You’ll normally find it in a lot of un-managed spaces like railways or fields and this can be for any number of reasons though sometimes it can be from dumping.
How can Japanese Knotweed impact your home?
Japanese Knotweed (Fallopia japonica) is native to eastern Asia and is an attractive looking, fast-growing plant with hollow bamboo-like stems, reddish stalks and large green heart-shaped leaves. In the autumn, it looks pretty as it has numerous tassels of white flowers. Innocent enough to look at the above ground, but this plant has an extensive and destructive root system. The roots force their way through cracks in patios, pavements, floors and walls causing extensive damage. Japanese Knotweed costs homeowners in the UK £166 million every year in herbicides, repair bills and property devaluation. All property owners should beware of Japanese Knotweed. it’s estimated that it could cost the government 1.5 billion pounds to eradicate it from the UK, it is illegal to plant it in the wild.
Mortgage lenders will not lend against a property affected by a Japanese knotweed problem.
What is Japanese Knotweed?
This extraordinary plant was first found growing on the slopes of Japanese volcanoes. In the mid-19th century, the German botanist, Phillipp von Siebold discovered the plant and sent samples to Europe. Today, Japanese Knotweed can be found in 26 European countries and 36 American states as well as extensively in Asia.
How to Identify Japanese knotweed
Identifying Japanese knotweed can be ticky so if you are ever in doubt it’s recommended to get a professional to look and they’ll be able to confirm as well as help with a treatment plan if they do discover an infestation. We’ve put together some top tips to look out for to help you discover japanise knotweed that we hope will enable identification.
up to 3m tall plant
‘shovel’ or ‘heart’ shaped leaves that are lush green
a zig-zag growth shaped stem with green/red flecks
Cream/white flowers in summer bloom
Red ‘shoots’ of growth in Spring similar to asparagus
Yellow/golden leaves in autumn
Hollow stem-like bamboo canes in winter (leaves will have died off)
If you’re buying a house and getting a (RICS aprooved) survey it will also normally find a knotweed issue and add it to their report, they will not be able to help with any treatment plans
How did it get to the UK?
Phillipp von Siebold was so excited about his discovery of the knotweed and other plants during his time in Japan, that he sent samples to the Royal Botanic Gardens in London and Edinburgh. To attract the general public, the botanists in both places decided to sell cuttings of the different plants – including knotweed- in their nurseries. Needless to say, over the following years, knotweed spread quickly with people share cuttings and disposing of unwanted plants which then grew wild and also with the help of the construction industry when houses and roads were being built.
The plant fit very with victorian style, like most styles though things go out of fashion and the plant was thrown over fences, dump and thus spread like wildfire across the country to the problem we have today. It also show-cased the problem with invasive species to the country, who knew!
Why is this plant so disliked?
Over the years, Japanese Knotweed has acquired a variety of nicknames including ‘monkey weed’, pea shooter’, ‘Hancock’s curse’and‘bullyweed’. Councils and homeowners soon realised that this was a very invasive plant that could cause tremendous damage, it is extremely difficult to completely remove.
Above ground, the plant quickly reaches 3-4 metres in height and although it dies back in the winter, it starts to grow rapidly in the spring – as much as 20 cm (nearly 8 inches) every day. That’s nearly 20 meters in 3 months, that’s taller than 3 houses! The plant tends to spread out more than up though. This means that if there is no more out it will start to crop up inside your house wherein lies the problem.
In Japan, growing on volcanic ash, the plant does not thrive nearly as well and in such areas remains relatively small.
Underground, the Japanese Knotweed has incredibly strong rhizomes that grow into a thick and complex network, often measuring more than seven metres in length and up to three metres below the surface. The rhizomes are very hardy and can survive temperatures as low as -35ºC.
In the UK, Japanese Knotweed is now very well established in the wild in many places and is classed as one of the top invasive weeds. It can have a negative impact on the biodiversity of the countryside and flood management and can cause damage to pathways, roads and buildings and importantly, knotweed has no predators. It is listed by the World Conservation Union as ‘one of the world’s most invasive species’.
Japanese knotweed removal
Japanese Knotweed is not easy to eradicate and experts estimate that it usually takes five years to successfully do so with chemical treatments or a large amount of topsoil has to be removed and destroyed by specialist facilities.
There are various ways to deal with it, but it must be remembered that even if a tiny amount of roots or stems are left behind by accident, the knotweed will soon re-establish itself with a vengeance. For more information see: https://www.rhs.org.uk/advice/profile?pid=218
Below are some methods but we highly recommend seeking professional advice before attempting to deal with the plant.
Japanese knotweed removal cost
Removal costs vary but you would be looking at a few thousand pounds and treatments can vary depending on which you select, if (for example) you selected chemical you would need to keep retreating the weed and there is no guarantee on its success so there can be a reoccurring cost for an option like that. We’ve covered some ways the weed is removed but we always recommend seeing professional help with any Japanese Knotweed infestation.
Cutting and burning knotweed
These two methods are really effective at clearing the fast-growing knotweed on the surface, but unfortunately neither damage the root system, so in both cases, the knotweed will soon re-appear, it’s not recommended as you may accidentally spread the weed.
Removing knotweed by digging
This is a very laborious task because of the intricate network of roots which must be carefully removed so that they remain intact – just 0.75g of root material (around a fingernail size) is all that is needed for the knotweed to grow again, so needless to say, this method is not always successful and best left to professionals who will normally give insurance backed guarantee on their work, they’ll also dispose of it.
If you do decide to tackle your knotweed this way, you will have to gather it all up really carefully so as not to leave any in situ and dispose of it all equally carefully as the Environmental Protection Act of 1990 lists Japanese Knotweed as ‘controlled waste’. This means that the knotweed must be taken to a licensed landfill site for disposal, this can have associated legal fee’s and we really don’t recommend attempting any DIY attempts which can sometimes just spread the weed instead of destroying it.
The correct herbicide must be used on the knotweed as it is essential that the herbicide permeates and destroys the root system. Chemicals containing glyphosate are usually needed and even then, they can take several years (and treatments) to totally eradicate the problem.
Having a Japanese knotweed specialist treat it is best, but will cost several thousand pounds.
Does knotweed have any positive points?
Although Japanese knotweed is not something anyone wants in their garden, it has had some positive benefits over the years. Botanists found that the white flowers of knotweed are very rich in pollen and are popular with bee keeps for this reason. In the northeastern states of the USA, ‘bamboo honey’ is popular and this honey is produced by bees that are fed on knotweed flowers.
Japanese Knotweed was planted in Welsh coal mining areas for many years to help stabilise the soil which it did very successfully. In China and Japan, knotweed has been used in herbal medicine for many years and the delicate young shoots are considered quite a delicacy in both countries’ cuisines.
What impact can it have on selling your home?
Despite the above plus factors, Japanese Knotweed in your garden is definitely not a strong selling point. Over the years the newspapers have carried heartbreaking stories of how the value of peoples’ homes has been halved because of the presence of knotweed. Japanese Knotweed is listed as an invasive weed and if house owners and landlords do not control it, they face prosecution.
Trying to sell your home if you have knotweed in the garden can still prove very tricky as lenders will not always give mortgages if knotweed is found in the property’s garden – or in the garden or within 7 meters of an adjoining house/ neighbouring land.
In 2012 because so many lenders were refusing to give mortgages on properties with Japanese Knotweed, the Royal Institution of Chartered Surveyors (RICS) had to publish a report giving guidance to surveyors – as Philip Santo from RICS explained at the time:
There is a real lack of information and understanding of what Japanese Knotweed is and the actual damage it can cause. Without actual advice and guidance, surveyors have been unsure of how to assess the risk of Japanese Knotweed, which can result in inconsistent reporting of the plant in mortgage valuations. RICS hopes that this advice will provide the industry with the tools it needs to measure the risk effectively and provide banks with the information they require to identify who and how much to lend to at a time when it is essential to keep the housing market moving.
With nearly 1.5 million homes affected by the weed, RICS is releasing new guidance (in 2021) to help homeowners fight back.
Nigel Sellars (RICS professional standards lead) said:
“We’ve launched this consultation ensuring the lending community, homebuyers and our chartered professionals get the opportunity to directly engage on how to dispel the myths and misconceptions, help unblock needlessly effected home sales and play our part in the built environment’s war on knotweed.
He then goes on to say…
“We will aim to publish a final version later this year, recognising how important it is to bring clarity to the marketplace as quickly as possible – particularly for those in need of help getting their property unstuck – and how to tackle knotweed with the latest expert advice.”
The Royal Institution of Chartered Surveyors (RICS) has issued new guidance on Japanese Knotweed, which came into effect on 1 September 2020. The guidance provides a framework for assessing the risk of Japanese Knotweed and sets out the steps that should be taken to manage it. The guidance advises that a specialist survey is carried out to identify the presence of Japanese Knotweed and assess the risk it poses to the property. The survey should also include an assessment of the potential impact on the property’s value. The guidance recommends that any treatment of Japanese Knotweed is carried out by a specialist contractor and that the method of treatment is appropriate to the situation. The guidance also sets out the steps that should be taken to monitor and manage Japanese Knotweed following treatment, including ongoing monitoring and management plans. The aim of the guidance is to provide a consistent and transparent approach to the assessment and management of Japanese Knotweed, ensuring that it is managed effectively and in a way that does not cause unnecessary damage to the environment.
What happens if you haven’t time to kill the knotweed?
Luckily, there is help available if you are keen to take advantage of the current buoyant property market. To save time and problems, trying to sell through a high street estate agent will be a bit of a nightmare as you won’t be able to get a mortgage lender to secure against the property.
You must declare Japanese knotweed, an affected property will be worth considerably less than the market value. If you are unsure about affected properties with knotweed you should seek legal advice on buying a property affected by Japanese knotweed.
it is still possible to sell your house to a cash buyer, quickly and effortlessly. True, the cash offer will be adjusted because your property has knotweed, but the huge advantage is that you don’t have to worry about lengthy procedures to kill it effectively, but just hand over the keys on the agreed date and head to pastures new, why not start the conversation with us today?
Do you have to tell the buyer about Japanese knotweed?
Absolutely, you are legally required to tell them if you are selling a house with Japanese knotweed. You will need to tell any buyers and/or estate agents, it can seriously affect the structure of the property and its value which is why it’s such a big problem.
Failure to declare it might result in legal issues. Normally it will be filled in a TA6 property information form by e.g. a surveyor if one is being used. You do not have to inform the government or the Environmental agency if you find the plant on your land.
How do I know if my house has Japanese knotweed?
Whilst it can be hard to find the difference we’ve made a guide on this page about the leaves (shovel-shaped) but if in double its always best to ask a professional to confirm, RICS approved surveyors are trained to look and can also help find the extent of the infestation and how much It might have affected the property. You can then focus on removing Japanese knotweed from the property with a treatment plan from a professional and stop any knotweed problems before they get too large due to how quickly the plant grows.
What distance from my house will Japanese knotweed have an affect on selling?
If Japanese knotweed is at a distance of 7 metres or more away from your house, it shouldn’t be an issue. If it’s less than 7m away from habitable space, it could cause difficulties selling your house.
Knotweed is separated into 4 categories: Category 1, Category 4, Category 1 or Category 4 More lenders are happy with Category 1 than 4, naturally, but there are deals for both, depending on whether the property is still habitable or not.
What do the Japanese knotweed results mean for the potential buyer?
If Japanese knotweed is found on residential property during a survey, it means that the property may have a higher risk of structural damage due to the invasive plant’s ability to grow through cracks in walls and concrete. This can result in potential damage to building foundations, walls, and drains, which can be costly to repair.
The presence of Japanese knotweed can also impact the value of the property and its saleability, as many mortgage lenders will refuse to lend against a property with a confirmed Japanese knotweed infestation.
As a potential buyer, it is important to carefully when purchasing properties, consider the results of a Japanese knotweed survey and seek professional advice on the best course of action, including potential management and removal options. It is also important to understand the legal obligations and responsibilities of the property owner in relation to Japanese knotweed management and removal.
What is the cost of dealing with Japanese knotweed?
The cost of dealing with Japanese knotweed can vary depending on the severity of the infestation and the chosen method of treatment. In general, it can range from a few hundred pounds to tens of thousands of pounds.
For example, using herbicides to treat Japanese knotweed can cost around £1,000 to £3,000 for a small infestation, while larger infestations can cost upwards of £10,000. Excavation and removal of Japanese knotweed can cost even more, ranging from £5,000 to £30,000 or more, depending on the size of the infestation and the complexity of the removal process.
What are the treatment options available?
There are several treatment options available for Japanese knotweed, including:
Herbicide treatment: This involves using specialist herbicides to kill the plant. This can be done through stem injection, foliar spraying or soil treatment.
Excavation and removal: This involves digging up the plant and removing it from the site. The plant and its roots must be disposed of at a licensed landfill site.
Permanent burial: This involves burying the plant and its roots in a deep hole. The hole is then covered with a non-permeable membrane to prevent regrowth.
Soil screening: This involves screening the soil to remove any pieces of knotweed roots. The soil is then replaced or treated with herbicide.
Biological control: This involves introdu
We’ve created a handy checklist – all the things you need to do and know before you selling a house