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Japanese knotweed (Fallopia japonica) is the UK’s most invasive non-native plant, and was brought into the country by our horticultural ancestors in the 1820s.
As its name suggests it originates from Japan, having evolved on the sides of volcanoes. It grows rapidly, with new shoots appearing in spring and growing to approx 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.
All plants in the UK are female, so 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.
There are hybrid 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. More on what is Japanese knotweed.
Japanese Knotweed has distinct characteristics which help to distinguish it from other plants. The optimal time to detect Japanese Knotweed is throughout mid-Summer – Autumn. If you have a plant and are not sure it is Japanese Knotweed, here are some characteristics to look out for:
Does it grow rapidly? (Japanese Knotweed grows incredibly quickly- it’s been reported it can grow 2cm a day!! The stems can reach heights of approx. 3m and the Rhizomes can spread approx. 4m in every direction).
Japanese Knotweed is relatively easy to identify, once you know what the characteristics are. A key point to look out for is the distinctive heart shaped leaves which grow in a zig zag pattern. If you’re wondering what Japanese Knotweed looks like, we also have a gallery of Knotweed images to help you with your identification. If you’re still unsure, you can upload and send us your images here and we will be able to help identify the species.
We have a large gallery of Japanese knotweed pictures to help you with identification. If you need any further assistance, please email us your pictures and we will be to assist with identification.
There are various myths about Japanese Knotweed which are incorrect – here are the top 5.
1. Japanese knotweed can grow through concrete
It is often claimed in the media that Japanese knotweed can grow through concrete. Knotweed actually can’t do this – what it will do is exploit joints, cracks and weaknesses in concrete and grow through them in search of light. The general rule of thumb is that if water can penetrate it, so can knotweed.
2. You can kill Japanese knotweed by cutting down the stems and pouring diesel/bleach/glyphosate into it
This will not ultimately kill knotweed, even if all the above ground growth has gone. Firstly, by cutting the plants down, you are stopping the internal workings of the plant, meaning water and nutrients will not be circulating around the plant – and nor will the chemicals you have applied! DIY treatments often shock the knotweed into a state of dormancy – giving you the impression it is dead, but once ground conditions have improved again, or the ground is disturbed, more often than not, the knotweed will grow straight back.
DIY treatment can also make it harder for knotweed removal experts to deal with an infestation, as it limits the options available. The other downside to DIY attempts is that they will not be supported by an insurance backed guarantee, so if you try to sell or re-mortgage the property, banks and building societies will be unlikely to lend.
3. It is illegal to have Japanese knotweed on your land
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.
4. Japanese knotweed spreads by seed
Every Japanese knotweed plant in the UK is female, meaning that flowers are not pollinated and do not therefore produce seeds. All of the plants in the UK have either been intentionally planted, spread naturally through the underground development of rhizome or have been accidentally moved from one site to another in infested soil.
A piece of rhizome the size of your thumbnail is enough to generate new growth, and as a pioneer species it can survive pretty tough conditions, going on to thrive where other species cannot.
5. Lenders will only accept work and guarantees from PCA members
One of the first questions many of our clients ask is ‘Are you a member of the PCA?’
Many news articles in the media state that mortgage lenders will only accept work completed by a PCA member. This is not the case, as there are many reputable and capable companies who are not members of the PCA but do offer insurance backed guarantees.
Our guarantees are underwritten at Lloyd’s, an A-rated insurer and are accepted by most banks and building societies.
Rhizome dormancy can be induced by incorrect herbicide application. Where dormancy exists, the Knotweed may look dead above ground (or may not even be visible) but the rhizome system in the ground remains alive ready to send up new shoots when the dormancy is broken.
Japanese Knotweed can cause damage to buildings, underground services and landscaped surface. The severity of this damage is sometimes somewhat overstated, although there are many recorded incidents where Japanese Knotweed has indeed caused damage.
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.
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, 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!
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 (e.g. 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 weaknesses.
Yes, Japanese knotweed can grow within cavity walls. We have 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. If you would like to talk to one of our team about your Knotweed problem, please call us today on 03335 777 666 and we will be happy to help.
Unfortunately, banks WILL refuse mortgages and loans against a property with Japanese Knotweed, preventing property sales, UNLESS a PCA approved Japanese Knotweed Specialist has been instructed to conduct a management plan. Lenders need to know that a reputable & specialist Japanese Knotweed company has been instructed in order to protect their investment
Other problems include:
Damage to built structures such as walls, conservatories and outbuildings.
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.
Firstly, you need to identify the scale of the problem. Look to have the Knotweed identified by a professional treatment firm 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.
Use our free Japanese Knotweed identification service here.
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.
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.
Importance of Insurance Backed Guarantees
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 treated and/or 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.
Insist on the job being done by a firm you trust will do the job properly
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.
It is true, many sales have fallen through as a result of Japanese Knotweed and lending policies. 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. It all very much depends on the site; the level of the Japanese Knotweed present and where it has come from and many other factors which are assessed on a house by house basis.
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 with all the information they need, it will help to ensure that the Knotweed issue isn’t blown out of proportion. Arm yourself with the facts.
Concealment is no way to go about pushing the sale of your house through. Not only are RICS surveyors highly trained in spotting Knotweed, it is also against the law due to the TA6 form. You should be aware that the Law Society’s TA6 form has a specific question relating to Japanese Knotweed and if answered untruthfully, during the conveyance process a legal claim of misrepresentation could possibly be brought against you by the buyer.
Yes, if the Knotweed is not being treated by a specialist company, 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.
There are legal, technical and financial issues that must be addressed.
> Developing a site with Japanese Knotweed
We are often asked: “What are the Legal, Technical and Financial Issues associated with developing a site without having first achieved complete removal of Japanese Knotweed?”
If you have a site you intend to develop you should completely remove the Knotweed before any construction works commence.
Japanese Knotweed is simply one of 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. There are a number of Japanese Knotweed removal methods that can be used to ensure complete removal.
> Removal or Control?
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
In the Pre-Contract Enquiry form (TA6) there is a specific question asking the seller ‘if the property is affected by Japanese Knotweed?’. If the seller fails to disclose Japanese Knotweed or knowingly falsifies the non-presence of Japanese Knotweed to the buyer, a claim against the seller could be brought before the courts for ‘Misrepresentation’.
Under the Consumer Protection Regulations, agents acting on behalf of the seller have a duty to disclose any “material facts”. Guidance to the regulations now includes Japanese Knotweed as a material fact.
If the Japanese Knotweed is in dormancy, we would strongly suggest you not to do this – if you are looking to redevelop/landscape or disturb the ground, complete removal (excavation) of the Japanese Knotweed is advised.
Japanese Knotweed Agency services will endeavour to keep disruption to a minimum, but inevitably some loss of enjoyment that the property and garden provides will be experienced. The amount and duration of disruption can depend on the treatment method adopted.
It’s possible that your company will be eligible for Land Remediation Tax Relief.
Tax relief for Japanese Knotweed treatment
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 (i.e. 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.
Specialist Tax Consultants can help to claim the tax that is rightfully yours for all Japanese Knotweed remediation undertaken since May 2001. 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.
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 legal claim where you can claim the cost of treatment and/or extraction against the party from where the infestation has come from. There are several different Japanese Knotweed removal methods that can be used to ensure that the Knotweed is treated completely, and insurance guarantees can be issued once the work has been completed.
There are Japanese Knotweed removal methods suitable for all cases. We know and understand the law and waste should be disposed of according to regulations. Please get in touch today on 03335 777 666 and we will be able to help.
There are several pieces of criminal and civil legislation relating to Japanese Knotweed.
Possible criminal sanctions under the Environmental Protection Act 1990 “Duty of Care” if you illegally consign Knotweed infested material, including soils, off site. Possible criminal sanctions under the Wildlife and Countryside Act 1981 if you cause or allow Japanese Knotweed to grow in the wild. Possible civil action in nuisance if your Knotweed encroaches or spreads into adjoining land. We work with lawyers specialising in Japanese Knotweed disputes.
The presence of Japanese Knotweed can have legal implications and consequences for neighbours, landlords, tenants, buyers and sellers of land and houses.
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 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.
Care must also be taken by a seller when answering enquiries before contract raised by a buyer. This is because he may become liable to the buyer if he makes a misrepresentation, sometimes even innocently and certainly if he has not made reasonable endeavours to check the position before giving answers.
There are potential 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” although there is some legal debate as to whether “private land” constitutes the “wild” for the purposes of the Act.
There are also 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.
Finally, the 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 infest are considered to be a controlled waste.
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.
Encroachment is the spread of Japanese Knotweed rhizomes (roots) across property boundaries. If you have exhausted all friendly attempts, then you can threaten legal action. This should not, however, be the first step.
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 an expert should be able to give an opinion based upon “the balance of probabilities”, the test required in a civil case. A site survey should be able to identify this.
Japanese Knotweed Agency has a full start to finish support program for those that need to go down a legal route to protect them and their home. If the adjoining landowner, the defendant, is seen to be taking reasonable steps to mitigate the nuisance that may in itself be a partial defence, but still cannot address any diminution or loss in value of your home due to the presence of Knotweed. However, we often see steps being taken that are not reasonable e.g. long treatment programmes and restrictions on use of the garden/property whilst the lengthy treatment programme is carried out.
If you think you are a victim of encroachment, please talk to us. We can help you. One of our expert associates can provide Japanese Knotweed expert witness services in accordance Civil Procedure Rules (CPR 35). We can also put you in touch with our panel of experienced Solicitors and Barristers, highly experienced in Japanese Knotweed disputes, and who can offer a representation service on a No Win No Fee agreement.
Call us on freephone 03335 777 666.
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 costlier. This may make it harder to obtain an insurance backed guarantee, which will be required by any non-cash buyer. Japanese Knotweed Agency can guide you through the process and be there to assist you in any way where Knotweed is involved.
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:
On instructing the Japanese Knotweed Agency to assist with your Knotweed problem, we will work with these other professional parties on your behalf. You can then rest assured that the Knotweed problem is in the hands of the professionals who are looking out for you. If the Japanese Knotweed is on your property because of a third party, a claim can be brought against that party for the treatment / removal costs and insurance guarantee; plus, recovery of any diminution to the value of your property.
A clear approach to eradicating Japanese Knotweed.
Please get in touch today if you would like to discuss your options.
It will depend upon your timeframes, site and budget.
What are the best methods for removing Japanese Knotweed?
We have various Japanese Knotweed removal methods available, and our team of experts will be able to recommend the most appropriate option for your circumstances.
What’s your objective – Japanese Knotweed removal or control?
Are you looking for complete removal or control, to prevent further spread and damage? In most circumstances, especially on development sites and in most gardens, complete Knotweed removal should be the objective. Where this is an unattainable goal e.g. Knotweed along a watercourse originating from Knotweed upstream, a control programme may be a more realistic objective.
What Japanese Knotweed removal methods are available?
If the affected ground is not going to be disturbed (e.g. by construction or landscaping works) AND you have plenty of time (at least one growing season, possibly more) before you want to achieve removal then an in-situ herbicide method may be suited. If not, you need to consider a physical removal method.
In-situ Herbicide Treatment
Herbicide treatment can result in eradication, although it is difficult and best left to a specialist in Japanese Knotweed eradication. The minimum time required is one growing season (typically May through to October) involving several applications of herbicide. This can either be applied by foliar spray, or in environmentally sensitive areas by stem injection. There is always a risk that viable rhizome remains after herbicide treatment so if you are likely to disturb the soils in the area, and re-growth cannot be tolerated, then you should look at a physical removal method.
Physical removal methods involve the excavation of all infested soil under expert supervision (typically to depth of 2m or more) followed by, either treatment, or disposal of that material. In certain circumstances complete excavation may not be possible e.g. restricted access, underground obstructions such as roots from trees protected by TPO, underground services, presence of groundwater.
What physical removal methods are available?
Once excavated the options for the further treatment or disposal of the excavated soils are:
Once we understand your Knotweed problem, we can recommend the most appropriate method for your situation. Call today on 03335 777 666 and one of our experts will be happy to help.
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 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 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.
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.
So, is it worth cutting corners when it comes to Japanese Knotweed? Is it not far better to get the job done properly in the first place? There are various Japanese Knotweed solutions available for all sites and situations, that will suit your budget and timeframe. Give us a call today on freephone 03335 777 666 or request a call back and we will be in touch.
Unfortunately, yes it does. If it has been treated with any kind of pesticide, there is a high possibility the rhizome will go into dormancy, making it more difficult to detect the scale of the Japanese Knotweed infestation & to give the infestation the appropriate amount of treatment in subsequent visits. If there have been attempts at digging or removing the Japanese Knotweed, it will be very difficult to recognize the original extent and spread of the plant.
A 5 year, in-situ, herbicide management plan is essentially a ‘control’ method which puts Japanese Knotweed into dormancy. As the rhizomes are not being removed from the soil, if the soil were to be disturbed, the Japanese Knotweed would become viable and start to grow again. Disturbing the ground could also fragment the rhizome system, leading to spread and regrowth of the Japanese Knotweed.