Japanese knotweed (Reynoutria japonica aka Fallopia japonica) is the UK’s most invasive, aggressive non-native plant. As its name suggests it originates from Japan, having evolved on the sides of volcanoes around 125 million years ago. A vigorous perennial, it grows rapidly, with new shoots appearing in spring and growing to approximately 3m high by June. It has pretty white flowers in the summer. In autumn the above-ground part of the plant dies back, leaving brittle canes left standing over the winter period.

More vigorous stems will appear the following year, gradually spreading to larger areas. Underground, the plants are supported by a crown that develops in mature plants, and an extensive rhizome and root system.

The rhizome network can penetrate deep into the ground, and often a few meters in all directions laterally. This is one of the reasons that Japanese knotweed is so troublesome, as new plants are easily created from very small pieces of the rhizome.

All plants in the UK are female, so thankfully, unlike other invasive plants such as Himalayan balsam or Giant hogweed, the seeds in the flower are not pollinated. All new outbreaks of knotweed result from fragments of viable rhizome that may be spread within soils being moved from site to site, by fly-tipping, by natural processes such as river bank erosion, or by animal movement.

Like so many of our garden plants, Japanese knotweed was imported as a specimen from overseas in the 1820’s. Philipp Franz von Siebold returned from Japan with many of our garden staples such as wisterias, hostas, peonies and hydrangeas. Unfortunately, Japanese knotweed was also in the collection. The plants were distributed and sold by nurserymen across the country, and were very popular, especially given it had been awarded a gold medal by the Agricultural and Horticultural Society in Utrecht. It was also noted for commercial and industrial applications, notably stabilisation of sand dunes and railway embankments.

By the early 1900s, reports were starting to come in of it being spotted outside of gardens in the wild. Comments were also circulating about its dominance and vigour in domestic settings. The plants quickly fell out of favour, however by that time it was too late. Japanese knotweed was now widely distributed, and during the 20th century spread across the entire country. In fact, we now believe that there is not a single 10 square kilometre patch in the UK where knotweed cannot be found.

Read more about the history of knotweed on our page about Japanese knotweed History

Japanese knotweed is relatively easy to identify, once you know what the characteristics are.

Key characteristics to look for include;

  • Asparagus-like spears emerging in spring
  • Bright green shield shaped leaves that form a zig-zag shape on the stem
  • Tall green canes, often with purple speckles
  • Clusters of creamy white flowers in late summer, early autumn
  • Brown, brittle canes left standing in winter

Visit our Identification Page and watch our 3 minute video on How to identify Japanese knotweed. We've also produced a Japanese knotweed Identification Guide, which you can download to help you identify the plant in situ.

If you are still unsure, we offer a Japanese knotweed identification service. Email your photos to expert@environetuk.com and we'll tell you if Japanese knotweed is present. This is a free service. However, if you would like to make a small donation to one of our chosen charities via JustGiving that would be much appreciated.

There are different varieties of Japanese knotweed, notably Giant knotweed, which has larger leaves and generally taller plants. It is not as invasive as Japanese knotweed, but has the same legal status and treatment methods. There is also Bohemian knotweed (a hybrid of Japanese and Giant knotweed) and Japanese knotweed var. compacta – a smaller, less widespread variety.  Take a look at our knotweed gallery to see what they look like.

There are also a number of plants that people commonly mistake for knotweed.  The best way to be sure what you are dealing with is to email us a picture for confirmation to expert@environetuk.com

That’s easy – just email us your pictures! Environet offer a free, same day identification service. Just send us some close-up pictures to expert@environetuk.com and we’ll let you know if it’s knotweed you’re dealing with. Once we’ve checked the pictures, we can talk you through the next steps.

Japanese knotweed isn’t always visible to the naked eye, for example during winter when the plant dies back, or if it’s been herbicide treated in the past it may be lying dormant beneath the ground and could begin to regrow at any moment. Sometimes people try to deliberately conceal knotweed, for example by laying a patio over it.

The only way to tell with a high level of certainty whether or not a property has knotweed is to commission a dog detection survey. We are proud to offer the UK’s only team of highly trained knotweed detection dogs, who can smell the unique scent of the plant’s rhizome beneath the ground at any time of year, even with no above-ground growth visible. They will scour the garden and freeze if they detect the presence of knotweed, allowing our surveyors to dig in the correct location and determine the extent of the infestation.

Japanese knotweed can cause damage to buildings, underground services and landscaped surfaces.

The severity of this damage is sometimes somewhat overstated, although there are many recorded incidents where Japanese knotweed has indeed caused damage. Watch our damage video to see some examples of what knotweed can do.

MD, Nic Seal has also written an interesting blog that you can read here.

Yes, damage can be caused to buildings by Japanese knotweed, particularly where the knotweed has been left to establish itself over many years. However, the extent is often overstated, and some of the horror stories you may read in the press or on the internet are there to sensationalise and scare you!

We have seen cases of knotweed causing damp problems, and have even experienced stems and healthy leaves emanating through vents and air bricks located 2m above ground level. When knotweed grows in cavity walls it has the capacity to force the two skins of the wall apart.

In the height of summer Japanese knotweed can cause a fence or wall to lean and ultimately fall.

Yes. Underground sewers, drains and land-drains are particularly susceptible to Japanese knotweed. The knotweed rhizome will find its way into the smallest hole on a pipe joint to find water.

The rhizome will continue to grow, gradually blocking the drain and finally breaking it apart. We also have anecdotal evidence of Japanese knotweed being spread down surface water drains. Pieces of rhizome break off the parent plant and are conveyed down the pipe, infesting the watercourse with Japanese knotweed at the point of discharge.

Yes, the most common form of property damage from Japanese knotweed is caused by laying a hard surface such as asphalt, patio slabs, driveway block paving, etc. over Japanese knotweed infested ground.

The knotweed will have no difficulty forcing its way through any weakness in the formation in its unstoppable quest for light. The general rule of thumb is that if water can go down through the cracks, then knotweed can grow up through it.

No, this is a very common misconception.

There are many recorded incidents of knotweed "growing through concrete", however what actually happens is that the knotweed finds a weak spot (eg a crack in the concrete, or an expansion joint) and grows through it, gradually prizing it apart. Knotweed will find the route of least resistance to get water and light. It gives the appearance of growing through concrete when it in fact has simply exploited the weakness. The general rule of thumb is that if water can penetrate it, so can knotweed.

It is true, many sales have fallen through as a result of Japanese knotweed and lending policies.

This being said, Japanese knotweed should not prevent a house sale being completed, it just adds a few steps in the process. Once the knotweed is controlled, with a suitable insurance backed guarantee, mortgage providers and others will lend. See our section on buying and selling property affected by Japanese knotweed for more information.

Yes, if the knotweed is not being treated by a specialist company. However, with the right treatment and insurance backed guarantee most banks and buildings societies will lend.

Mortgage lenders including the building societies and high street banks refuse to lend money in the form of a mortgage where their surveyor identifies the presence of Japanese knotweed on the property. Refusal has also resulted where no Japanese knotweed is present on the site, but is on adjoining land. Surveyors employed by the banks are instructed to look out for Japanese knotweed.

Banks refuse mortgages because the plant can cause significant property damage and can devalue the property due to the risk level this poses. This affects the loan to value ratio and reduces the value of the security held by the bank. Lending money on a property with untreated knotweed is just a risk the banks are not willing to take.

The good news is that we do have several residential solutions with an Insurance Backed Guarantee (IBG) underwritten by an “AA-“ rated insurer that satisfies most lenders. Our Japanese knotweed removal methods range from herbicide treatment programmes using foliar spray, or in some cases stem injection, to DART™ which is a method that combines root/rhizome removal with herbicide treatment, and finally physical removal methods such as Resi-Dig-Out™. For much larger areas our commercial Xtract™ or Dig & Dump solutions may be appropriate. Our work is offered with an insurance backed guarantee, which provides security for the lenders and yourself as the homeowner. If regrowth is experienced during the time of the guarantee, we will treat this at no extra cost.

If you are a buyer or seller with hugely different perceptions of the scale of the knotweed problem and can't agree on apportionment of costs, you may find our Survey and Japanese Knotweed Management Plans of use. These can be commissioned by buyer, seller or jointly, to ensure a completely impartial view is given by a professional firm. Once this report is completed, we would be able to undertake the removal work at a fixed cost, and provide a guarantee that can be assigned to the new owner upon completion of the sale. Find out more about our residential solutions

If you would like more information on how we can help you ensure your mortgage goes through, please contact us on 01932 868 700 or complete our form and we will be in touch shortly.

A property with Japanese knotweed on the land can make for a difficult sale. Buyers would much prefer to buy a knotweed-free property because it is one less thing for them to worry about. This is where you as the seller need to make the most out of the situation, in order to make your property attractive to potential buyers. If you can provide the prospective buyer with all the information they need, it will help to ensure that the knotweed issue isn't blown out of proportion. Environet can guide you through the whole process. We have helped hundreds of clients sell their properties. Here is our list of dos and don'ts.

1. Don't stick your head in the sand! Concealment or hoping that nobody will notice the knotweed is no way to go about pushing the sale of your house through. Firstly, RICS chartered surveyors are trained to spot knotweed, and are obliged to report its presence either on your property or within 7m of your boundary. Secondly, you are actually breaking the law. The Law Society's TA6 form has a specific question relating to Japanese knotweed and if answered untruthfully during the conveyancing process a legal claim of misrepresentation could be brought against you by the buyer down the line.

2. Do it the right way the first time. You should look to commission a reputable Japanese knotweed removal firm to remove the knotweed and provide suitable guarantees. Don't fall into the trap of applying home remedies to Japanese knotweed - any DIY attempts will not be supported by banks. These inappropriate treatments can actually induce rhizome dormancy and make any subsequent treatment more difficult and costly. This may make it harder to obtain an insurance backed guarantee, which will be required by any non-cash buyer.

3. Get an expert on board you can trust. You should instruct a Japanese knotweed removal firm to carry out a full site survey, producing a Japanese Knotweed Management Plan. This will assess and report on:

  • The full extent of the knotweed including its rhizome system
  • The likely source or origin of the knotweed
  • The location in relation to knotweed encroachment issues
  • Whether building damage has been caused by knotweed
  • Site specific conditions that might influence the treatment methodology
  • Full quotation detailing the chosen removal method

At Environet, we have Japanese knotweed removal methods suitable for all jobs, so don't panic if it is a small garden with no access for machinery. Once you have received the report, you will have all the information required to make a clear, knowledgeable decision on whether you want to engage a firm to remove the knotweed or reduce the price of your property and leave the buyer to deal with the issue. For a quick sale, this option is only practical for a cash buyer.

4. Choose the right method and secure the right guarantees. When you are selling your property, you need to consider the requirements of any potential purchaser. It is tempting to choose the cheapest option and hope for the best - after all, you will not see the benefit of the money spent as you won't own the property! But we think you'll agree that this is short sighted - after all, you don't want to find yourself unable to sell the property. Firstly you need to ensure that any work you instruct comes with a decent insurance backed guarantee that will be fully transferable to the new owner and accepted by all of the major lenders. Then you need to think about the method of removal. A buyer is likely to be less inclined to make you an offer if they can't use the garden for 3 years because of an ongoing treatment programme; but you may not have the funds to pay to have the knotweed fully excavated. Take the advice of experts in the industry, and don't be afraid to ask questions before you settle on a solution. You can then rest assured that the knotweed problem is resolved and potential buyers and lenders should find no reason to worry about the knotweed, allowing for a smooth sales transaction.

There are many horror stories in the press and on the web which tend to overstate the reality. However, you should treat this highly invasive plant with the respect it deserves - it frequently wins the battle against DIY amateur attempts. That said, if this is the house of your dreams, don't let the knotweed make it a nightmare. If treated correctly, Japanese knotweed can be eradicated, leaving you to enjoy your house for years to come. Here are our top 5 tips;

  1. Identify the scale of the problem. Look to have the knotweed identified by a professional as there are many plants that are often mistaken for Japanese knotweed. You can send us any pictures of the suspect plant, and we will identify it free of charge. Find out more about what is Japanese knotweed here.
  2. Understand the liabilities that you'll be taking on. Make sure you understand the liabilities the knotweed presents, because it will be your responsibility as the new owner. Encroachment can be a big issue with knotweed, as knotweed does not respect boundaries when it grows. Has the knotweed encroached onto your land from another property, or did the knotweed originate on your land and spread outwards? If there is a case for encroachment, then the first discussion you have with your new neighbours may not be as friendly as you had hoped.
  3. Think about potential damage.  If the knotweed is growing close to the property, it may have caused damage to the building. This may not be immediately obvious, but knotweed can cause damage especially to underground elements such as drains. The extensive underground system can spread much further than what you see above ground. A site survey is recommended to ensure the full extent of knotweed is examined. This survey will also try to determine where the knotweed originated from, an important fact if you are facing an encroachment claim.
  4. Consider your mortgage requirements.  Perhaps most importantly you could have difficulties securing a mortgage on the property, purely as a result of the knotweed. Some lenders reject outright any property affected by knotweed. Others take a more pragmatic view and lend where the knotweed is being removed by a reputable firm and where appropriate knotweed insurance backed guarantees are provided. Speak to your mortgage provider to see what type of guarantee they require. Some ask for a 5 year guarantee and others ask for a 10 year. Make sure you understand what your mortgage provider requires before speaking with a knotweed removal company, as this will ensure you gain the correct level of coverage required.
  5. Stay involved.  Don’t fall into the trap of letting the seller “sort out” the knotweed problem. On too many occasions we see a cheap attempt at removal with inadequate guarantees. Insist it is carried out by a firm that you trust will do the job properly and will be accepted by your mortgage provider - otherwise walk away.  If the work has been carried out already, ask to see all of the documentation available – and get it checked by a reputable professional. Environet was established in 1996 and we have Japanese knotweed solutions suitable for both the commercial and residential sectors. We provide our unique market leading insurance backed guarantee underwritten by an “AA-“ rated insurer – you won’t find any better security than that. Let us worry about removing the Japanese knotweed, and you just focus on making your new house your home.

Environet has a clear approach to eradicate knotweed:

  1. Preparation of Japanese Knotweed Management Plan, including Site Survey
  2. Agree scope of removal work
  3. Undertake removal works
  4. Issue Insurance Backed Guarantee underwritten by an “AA-“ rated insurer

Once these steps have been completed, the purchase can go through without the knotweed being a limiting factor. Give us a call today on 01932 868 700 to discuss your options.

There are several pieces of criminal and civil legislation relating to Japanese knotweed.


Wildlife and Countryside Act 1981

There are criminal sanctions under the Wildlife and Countryside Act 1981 under which it is an offence to cause or allow Japanese knotweed to grow in the wild.

Environmental Protection Act 1990

Environmental Protection Act 1990 includes provisions including a “duty of care” for the storage, processing, treating and disposal of controlled waste. Japanese knotweed and the soils it infests are considered to be a controlled waste.

Town & Country Planning Act 1974

There are powers under the Town & Country Planning Act section 215 for Local Authorities to force landowners to clear up land if it detracts from local amenities, including that infested by Japanese knotweed. The Town & Country Planning Act is also often used by Local Planning Authorities by way of planning conditions to force developers to remediate sites infested with knotweed.

Anti-Social Behaviour, Crime and Policing Act 2014.

Part 4 of the Act introduced Community Protection Notices and Remedial Orders. The community protection notice can be used against individuals who are acting unreasonably and who persistently or continually act in a way that has a detrimental effect on the quality of life of those in the locality. The Anti-social Behaviour, Crime and Policing Act 2014 does not explicitly refer to Japanese knotweed or other, similar invasive non-native plants, as the new anti-social behaviour powers are intended to be flexible. However, frontline professionals can stop or prevent any behaviour that meets the legal test in the powers.

The notice can be used to require someone to control or prevent the growth of Japanese knotweed or other plants that are capable of causing serious problems to communities. The test is that the conduct of the individual or body is having a detrimental effect of a persistent or continuing nature on the quality of life of those in the locality, and that the conduct is unreasonable. Under section 57 of the Act, “conduct” includes “a failure to act”.

Infrastructure Act 2015

The Infrastructure Act 2015 gives environmental authorities in England and Wales the power to issue species control orders. These orders will make it possible to compel land owners or occupiers to carry out control or eradication operations, or allow them to be carried out by the issuing authority.

Breaching a species control order will be a criminal offence, but owners or occupiers will have the right to appeal to a tribunal and, where relevant, may be compensated for any damage caused by the eradication work.


The presence of Japanese knotweed can have legal implications and consequences for neighbours, landlords, tenants, buyers and sellers of land and houses.

Civil Nuisance (Encroachment)

In the case of Japanese knotweed spreading from one owner’s land to a neighbour’s land the landowner could face a legal claim by the neighbour. This is because under the common law of nuisance a landowner must take reasonable steps to prevent a nuisance which may cause damage spreading from his land to neighbouring land. Generally liability will only arise after the owner has been made aware or should have reasonably been aware of the problem. However, there is a legal argument which could be made to suggest that where the Japanese knotweed has been brought on to the land by the landowner and spreads to the neighbouring land he has a strict liability to his neighbour irrespective of whether the steps he has taken to prevent it from spreading have been reasonable or not.

In either case, the claim is likely to be for damages for the cost of eradicating it from the neighbouring land and/or an injunction forcing the landowner to take steps in regard to its treatment.  In February 2016, in the landmark case Waistell vs, Network Rail - Recorder Grubb found that Mr Waistell had successfully made out his claim in private nuisance against Network Rail. It was found that not only had Mr Waistell’s property suffered from encroachment, but also that the mere presence of knotweed on Network Rail’s land was an actionable interference with the use and enjoyment of Mr Waistell’s land. As a result, Mr Waistell was awarded damages for the cost of treatment and the residual diminution in value of his property after the treatment had been carried out.

The case is significant as it holds big landowners to account and imposes a positive duty on them to ensure that any knotweed that is on their property is not preventing neighbouring landowners from being able to sell their property for market value.  Failing to comply with this obligation will result in awards for damage for the cost of treatment of the knotweed and any residual diminution of value.

In the case of landlords and tenants, depending on the wording of the lease and also whether the Japanese knotweed was present when the lease was entered into, a tenant may find himself unwittingly liable to his landlord under the terms of his lease to have any Japanese knotweed on the demised property treated or removed.


In this context, a misrepresentation is a false statement of fact (relating to the presence of knotweed) made by the seller to the purchaser, which induces them into purchasing the property and causes them to sustain a loss.  It does not need to be the only factor which induced the sale.

The starting point is ‘The Law Society’s Property Information Form’ (TA6) question 7.8.  This requires the seller to say whether the property is affected by knotweed and specifically asks:

“Is the property affected by Japanese knotweed?”

The seller then has the following tick box options available; ‘Yes’, ‘No’ or ‘Not known’.

If the seller ticks either ‘No’ or ‘Not known’ to this question but they did in fact know of the presence of knotweed on the property then it is likely that they have committed a fraudulent misrepresentation. 

If they ought to have known about the presence of the knotweed or ticked ‘No’ and had no reasonable grounds for believing that the property was not affected by knotweed then it is likely that they have  committed  a negligent misrepresentation.  An example of negligent misrepresentation would be where the seller knew a plant was growing in the garden but took no steps to seek to identify it prior to completing the TA6.

We have written extensively about misrepresentation in our blogs.  To read more, click here.

There are many laws surrounding knotweed, which can be confusing.

Japanese knotweed is not a notifiable weed nor is it illegal to have it growing on your property as long you don’t allow it to spread onto adjoining land. If this happens, either a civil nuisance claim can be brought against you for allowing the knotweed to encroach onto private land, or you may be committing a criminal offence under the Wildlife and Countryside Act 1981 if you have caused Japanese knotweed to grow in the wild. 

Japanese knotweed is not fussy about where it grows, which is demonstrated in our gallery of knotweed pictures. It has an uncanny desire to grow along and across property boundaries, without any respect for boundaries. It spreads its invasive rhizomes and continues to encroach and wreak havoc until action is taken against it.

The damage Japanese knotweed can cause should not be under-estimated, so if you notice Japanese knotweed encroaching onto your land, you should take immediate action.

Notify the adjoining landowner of the problem, preferably in writing. A co-ordinated approach that tackles the Japanese knotweed on both pieces of land is much more likely to be successful than piecemeal attempts.

Talk to us about a Treatment Plan and try and agree with the adjoining landowner the allocation of costs. We have a number of different Japanese knotweed removal methods we can use, to ensure that the knotweed is completely removed.   If required, Guarantees can be issued to both properties once the work has been completed.

If you can’t agree a way forward with the adjoining owner, (some are more receptive and motivated than others) then your options are to look for a Japanese knotweed control method, such as using herbicides and/or vertical root barriers or to seek legal redress.

Japanese knotweed is not fussy about where it grows and has no respect for property boundaries.

The first thing to do if you notice Japanese knotweed encroaching from a neighbouring property is to notify the adjoining landowner of the problem, preferably in writing. A co-ordinated approach that tackles the Japanese knotweed on both pieces of land is much more likely to be successful than piecemeal attempts. Talk to us about a Treatment Plan and try and agree with the adjoining landowner the allocation of costs.

If you can’t agree a way forward with the adjoining owner, then you could look for a control method, such as using herbicides or vertical root barriers. We can advise you on the best course of action.

Legal action should be a last resort, but it is against the law to knowingly allow knotweed to spread to an adjoining property - so if you have given your neighbour notification and they have refused to act, you are within your rights to take action to protect your home.

The legal remedy for knotweed spreading onto your land from adjoining land can be found in civil nuisance. To bring a successful claim, the claimant needs to demonstrate that the knotweed originated from the adjoining land and that the knotweed is causing the claimant owner "nuisance". It's not always easy to prove the knotweed origin, but we are usually able give an opinion based upon "the balance of probabilities", the test required in a civil case. A site survey will provide evidence to support this.

If you think you are a victim of encroachment please talk to us. We can help you. One of our experts can provide Japanese knotweed expert witness services in accordance with Civil Procedure Rules (CPR 35). We can also put you in touch with lawyers, highly experienced in Japanese knotweed disputes.

In May 2020 we launched our highly trained detection dog team. Labrador Retrievers Mick and Mack, along with Cocker Spaniel rescue dog Buddy, are trained to detect the unique scent of Japanese knotweed rhizome beneath the ground, meaning they can identify the plant’s presence where a human surveyor cannot. They can cover a garden or construction site in a matter of minutes and will indicate by freezing and pointing with their noses to the ground where the scent of knotweed is detected, even in small quantities. Our expert surveyors can then dig in the precise location the dog has indicated to determine the extent of the infestation.

Our detection dogs are useful to buyers, sellers and homeowners who need reassurances that a property is knotweed-free, or who wish to understand the extent of an infestation since visible above-ground growth is not always a reliable indicator. Whether you’re a buyer checking a property you hope to purchase, or a seller wishing to have their property thoroughly checked, the detection dogs will remove any uncertainty around Japanese knotweed. Our homes are often our most valuable assets and a dog detection survey is the best way to ensure it is knotweed-free and its value is preserved.

Developers and construction firms can check sites for Japanese knotweed prior to purchase or development, helping prevent unexpected delays to construction schedules further down the line. If knotweed is present, the dogs can help determine the extent of the infestation, enabling us to put an appropriate remediation plan in place as early as possible.

A dog detection survey is the only way a homeowner or landowner can say with a high level of certainty that a property or site is clear of Japanese knotweed. Testing shows that our detection dog team will accurately detect Japanese knotweed in 95% of cases where it is present, including infestations hidden beneath the ground where a surveyor would be unable to verify its presence. Environet provides an insurance-backed guarantee on sites declared knotweed-free following a dog detection survey, meaning you’re covered for remediation costs in the highly unlikely event knotweed is subsequently discovered.

We work in partnership with professional dog handlers RFA Security, longstanding experts in training dogs for security detection work, who are responsible for the welfare of the dogs. An independent company-wide audit is performed every year to ensure the highest possible standards of animal welfare are maintained. Mick, Mack and Buddy live with their handlers as part of their family and have a very close relationship with them. There are also kennels on site where the dogs are cared for during the day when they are not working. Dedicated kennel staff are on duty at all times to meet the dogs’ needs, including feeding, playing, cleaning and exercising.

No, there are only a few in the country. Environet, working with RFA Security, was the first company to offer a Japanese knotweed dog detection service in the UK. This is a unique service for our customers, meaning we’re able to offer the most accurate and reliable knotweed surveys on the market.

There are legal, technical and financial issues that must be addressed.

Japanese knotweed is simply one of the things in life that should not be brushed under the carpet with a botched attempt at removal, unless of course you want to incur delays and major expense at a later stage. While it may seem like a large task to remove Japanese knotweed, you are better off sorting the problem out at the beginning, before any works start. We have a number of Japanese knotweed removal methods that can be used to ensure complete removal.

Many attempts at "controlling" Japanese knotweed are counterproductive. They kill off some of the plant, leaving the majority of the rhizome system below ground in a state of temporary dormancy, ready to resurface when you least expect it. There may be no obvious evidence of the knotweed above ground, but you can be pretty sure that viable rhizome remains. This is what we see in a lot of DIY attempts. The plant looks dead, but it is in fact dormant.

Imagine a development site where viable knotweed rhizome remains hidden in the ground, possibly to a depth of 2m or more, having laterally spread into areas you might think are unaffected. Once you disturb these soils whether by ignorance, accident or intentionally, you would almost certainly fragment and spread the knotweed rhizomes to other areas of your site. This would significantly increase the scale of the problem, and hence the cost of remediation.

All too frequently we are called in to help with removing Japanese knotweed, because other less experienced operators have failed to completely kill off the knotweed.

The legal implications of a knotweed infestation

Make sure you understand the law before tackling Japanese knotweed. If you caused the knotweed to be spread off-site, you could find yourself at the wrong end of criminal proceedings under either the Wildlife and Countryside Act 1981, or the Environmental Protection Act 1990 "duty of care". Offences under these Acts can result in custodial sentences. If you consign knotweed infested soils off site other than strictly in accordance with these legislative requirements, whether intentionally or not, you will run the risk of prosecution.

The technical implications of removing knotweed

Botched attempts at treatment or removal make it considerably more difficult for professionals to completely remove the knotweed for you. Trying to find and remove every piece of viable rhizome is akin, albeit with a difference, to finding and removing all fragments of asbestos that may or may not be in the ground. The big difference being that asbestos does not grow, so usually stays buried out of sight, whereas viable Japanese knotweed rhizomes are living and will grow to the surface, pretty much irrespective of what is put in its way. Imagine it growing through your asphalt driveways/roads just as you are nearing completion of the build – it would have pretty dire consequences on the saleability of the property and in many cases financing.

Where knotweed exists, either within the curtilage of a property or on adjoining land, virtually all UK banks and building societies will refuse lending until it is removed and Insurance Backed Guarantees (IBGs) "from a reputable company" are in place. We know because we receive lots of calls from distressed vendors of properties who have usually just lost a buyer due to funding being refused. Please don't think that funding will never be granted - once an insurance backed guarantee is in place, the lending should be granted.

The financial implications of a removing Japanese knotweed

Not surprisingly, the financial consequences can be pretty steep. It is not just the cost of remediation you should consider. Many main contractors/developers will be reluctant to take on the risk associated with a site infested with Japanese knotweed. Those prepared to take the risk inevitably price the risk, which of course gets reflected in the purchase/tender price.

If the risk remains with the client and knotweed is subsequently found, then additional costs during the construction stage are almost inevitable to cover professional fees, considerable management time, additional site precautions and delays to the contract, plus of course the cost of remediation. The cost of remediation in these circumstances escalates due to the urgency, as the more cost-effective alternatives to dig & dump may not be available.

Removing the problem prior to letting the main contract is the best solution all round.

It’s possible that your company will be eligible for Land Remediation Tax Relief.

Land Remediation Tax Relief, known as LRTR, was introduced under the Finance Act 2001 for all companies involved in the remediation of contaminated land, whether for commercial or residential purposes. For corporate bodies LRTR is available at 50% for developers (ie those trading in property), whilst property investors or owner occupiers can benefit from 150% relief against their qualifying expenditure. If you are not a corporate body the tax relief is not available.

The legislation currently permits any expenditure that prevents, minimises, remedies or mitigates the risk of any harm being done to people, property or the wider environment. The harm, or potential to cause harm, must be as a result of a substance or substances in, on or under the land to be applicable. “Substances” include for example heavy metals, hydrocarbon contamination and, arguably Japanese knotweed.

Environet works with specialist Tax Consultants to claim the tax that is rightfully yours.

Landfill Tax is now charged generally at the standard (higher) Landfill Tax rate for disposal of contaminated soils following the removal of the exemption in 2008, significantly increasing the cost of the Dig & Dump solution.

Environet have various Japanese knotweed removal methods, such as Xtract™. This provides on-site remediation of land infested with Japanese knotweed that not only avoids the punitive costs of Landfill Tax but is also eligible for relief under LRTR.

Contact us today on 01932 868 700 for further information.