How To Get Rid Of Japanese Knotweed

By Paolo Martini on 2nd July 2019 (updated: 18th November 2020) in News

There is no quick fix to killing Japanese knotweed infestations. No matter the size of your infestation, completely eradicating this pest can take years [1]; cutting corners at any point in the process could lead to a never-ending battle or, worse still, a hefty fine.

How you go about tackling your knotweed infestation will depend on your situation. If you’re looking to sell up your property soon then you’ll be seeking to get a chemical treatment plan in place that will placate potential buyers and mortgage lenders.

If you’re not planning on selling your knotweed-infested home in the near future then you may be happy to just control the plant’s growth. If you’re planning on building or developing land with Japanese knotweed then you may wish to remove it altogether. Remember, before you get a management plan in place, you’ll want to be certain that you’ve found Japanese knotweed on your land, rather than a look-a-like.

How to kill Japanese knotweed

Killing Japanese knotweed is not a task to be undertaken lightly. Knotweed is one of the most commonly found invasive plants to have landed in the UK [9] which requires professional chemical treatment in order to properly eradicate. Many mortgage lenders will not deal with your knotweed infested property unless you have proof that you have had chemical treatment completed by a PCA accredited company.

What is the best way to kill Japanese knotweed?

The best way to kill Japanese knotweed is with a professional-grade glyphosate treatment plan [10] administered by a PCA-accredited firm that can offer a guarantee which will be trusted by mortgage lenders and potential buyers. Professional firms have access to stronger chemicals than the general public, which means they get the job done quicker and should be able to offer you an insurance backed certificate. This certificate will prove that you’re actively working to deal with the infestation and will cover you for a stated number of years.

When writing about the Swansea University Japanese Knotweed Trials, Nic Seal said:

“It is possible to completely kill knotweed using herbicide, if applied correctly. The time it takes will depend on site conditions and in particular the maturity of the plant and the size of its underground rhizome system. Smaller infestations can be killed in two years, larger ones may take three or more years.”

What herbicide kills Japanese knotweed?

The best commercially sold herbicide to kill Japanese knotweed is Roundup Tree Stump. This product comes recommended by the RHS [2] and includes specific instructions on how to use it for killing Japanese knotweed. The herbicide is applied to either the cut canes or is painted using a foliar spray. Other herbicides that are reported as killing Japanese knotweed are SBM Job done Tough Weedkiller and Roundup Ultra.

Whenever using a herbicidal weed killer it’s important to follow all instructions to the letter. Non-selective weedkillers have the capacity to damage any biological matter they touch, following the instructions will ensure you make the most of your investment whilst minimising any potential damage to yourself or the environment.

Will vinegar kill Japanese knotweed?

There is no scientifically backed evidence to suggest that vinegar will kill Japanese knotweed. Although there has been some amateur research conducted on the topic, the use of vinegar to kill or control Japanese knotweed is not recommended by any governmental guidance or professionally accredited firm.

Will bleach kill Japanese knotweed?

Bleach does not kill Japanese knotweed. While bleach is a hazardous chemical that will certainly have an effect on the plant, it does not contain the necessary properties to kill Japanese knotweed down to its rhizome root system. Bleach is intended for use around the home as a disinfectant and is not suggested as an herbicide.

Will Roundup kill Japanese knotweed?

Roundup, as well as other glyphosate-based herbicides, is an effective tool to control the spread of Japanese knotweed [1], however it can not always be relied on to fully eradicate an infestation, especially the larger ones. Although it’s possible to control a small Japanese knotweed infestation with off-the-shelf chemicals, professional treatment companies have access to concentrated herbicides which deliver results at a much faster rate.

Will diesel kill Japanese knotweed?

There is no evidence that diesel kills Japanese knotweed. Diesel is a fuel that is not intended for use in the garden. There have been numerous studies [11] undertaken that prove the damaging effect that diesel can have on ecosystems, not to mention domestic gardens. Using diesel as a herbicide will not kill Japanese knotweed.

Methods For Getting Rid of Japanese Knotweed

Cutting Japanese Knotweed

You’ll need:

  • A saw, secateurs or shears
  • A container or sack to hold cuttings
  1. Isolate are affected by Japanese knotweed and mark it clearly.
  2. Use sharp tools to cut down any growth, making sure to collect all cuttings.
  3. Dispose of all cuttings legally, preferable on-site by either burning or burying.
  4. Then either smother the growth with a cover, treat remaining vegetation with herbicide or dig up.

When should you not cut Japanese knotweed?

Cutting down Japanese knotweed is not always an effective method of controlling an infestation. Cutting off its leaves may limit its ability to grow above ground, but the rhizome structure will continue to grow beneath the ground and by the next summer you will be dealing with more growth than before. Cutting or trimming the plant will also increase the chance of the knotweed further dispersing on your land. Should you fail to dispose of the cuttings properly you may inadvertently allow the plant to spread into neighbouring properties, which is an offence in the eyes of the law [7].

Digging up Japanese Knotweed

You’ll need:

  • A micro digger or similar vehicle
  • A skip or licensed waste removal van
  1. Isolate the area affected and ensure that no one else passes through whilst you are excavating.
  2. Use your micro digger or similar machinery to dig out the entirety of the infestation.
  3. Arrange for a licensed waste removal firm to take away the soil and plant matter, or find a suitable place on-site to bury the Japanese knotweed and cover with tarpaulin.
  4. Ensure that all vehicles and people are free from Japanese knotweed matter when leaving the site.

How do you remove Japanese knotweed?

Removing Japanese knotweed from your land requires patience and close attention to detail. The rhizome system is the toughest aspect of the plant to remove, roots can bury themselves 7ft underground [2] so you’ll need heavy machinery to do the job properly.

You’ll also be legally required to responsibly get rid of the plant matter and if you miss the smallest fragment your problem will return next season. Once all the knotweed material has been isolated there are governmental guidelines [1] that you will need to abide by when it comes to moving the plant off your land.

Using Herbicide to Kill Japanese Knotweed

You’ll need:

  • A herbicide treatment such as Roundup ProVantage 480, Rosate Glyphosate TF and Gallup Glyphosate Home and Garden Weed Killer
  • Protective clothing including gloves and mask
  1. If using a foliar sprayer, isolate the area and remove any plants or vegetation that you do not want harmed by the herbicide treatment.
  2. Preferably before the height of summer, use either a foliar sprayer or preferably a specialised herbicide injection gun to treat every plant within your chosen area.
  3. The glyphosate treatment will be transferred into the knotweed’s rhizome system and the plant will slowly die back over the next year.
  4. Return in subsequent years to check on any surviving growth and treat as before.

How do you spray Japanese knotweed?

Whilst it has a fierce reputation in the property industry, Japanese knotweed is not poisonous and is a plant that can be treated with herbicide treatments. There are two methods that treatment firms use to spray herbicide on Japanese knotweed infestations.

The first method is to paint the leaves during the summer with glyphosate herbicide. At this point in its lifecycle, the plant uses its leaves to collect nutrients and feed its rhizome network. Painting the leaves in this manner causes the foliage to die back and also delivers the chemicals to the root system.

The second method is via injection through the stems. Professional firms often come armed with trade-specific tools, such as injection needles which are designed to perforate the knotweed steam and inject the glyphosate directly into the plant. This kind of treatment can be done during the summer, as well as the autumn and winter, after the leaves have died back.

Burying Japanese Knotweed

You’ll need:

  • A micro digger or similar vehicle
  • Tarpaulin, old carpet or root barrier membrane
  1. Use a micro digger or similar machine to excavate a hole to bury the Japanese knotweed matter, according to government guidelines it should ideally be at least 5m deep. If you do not have access to machinery, then a depth of 2m is acceptable but all Japanese knotweed must then be wrapped in root barrier membrane.
  2. Isolate the area affected by Japanese knotweed and then dig out the entirety of the infestation. Either shift contaminated soil directly into your excavated hole or deposit in a skip first before burying.
  3. Once all Japanese knotweed contaminated soil has been transported to your hole, cover with a root barrier membrane or similar material and then fill back in with excavated soil.

Can you bury Japanese knotweed?

Burying Japanese knotweed is a viable method of controlling an infestation, however if not executed properly, it’s possible to inadvertently exacerbate the problem. It’s worth bearing in mind that this plant has been found growing in some of the most extreme climates imaginable, including areas of volcanic activity in its native Japan.

The most effective means of burying the plant is with the aid of a root barrier membrane [8], which are readily available online, and stop further growth before it reaches the surface, effectively containing the plant underground. It’s important to note here that you should not bury any other kind of waste with your Japanese knotweed, it’s also a good idea to check with the Environment Agency first to ensure that you’re acting within the law.

Burning Japanese knotweed

You’ll need:

  • A saw, secateurs or shears
  • A container or sack to hold cuttings
  • Space on your land to start the fire
  • Fire accelerant
  • Permission from the council
  1. Isolate the area affected by Japanese knotweed before cutting any vegetation.
  2. Remove every fragment of the Japanese knotweed infestation before a fire is lit. It’s important that you do not further spread the plant in the process of isolating it.
  3. Once all the material has been collected it can be burned privately, although you should check with your local council before doing so.
  4. Once the fire has burned out it is likely that crowns and rhizomes will still remain active, these should then be buried as described earlier, or removed by a registered waste carrier to a licensed disposal site.

Will burning kill Japanese knotweed?

It is possible to kill Japanese knotweed by burning it, however this is rarely a fool-proof method and often leads to remnants of the plant remaining intact. Preventative steps must first be taken to remove every fragment of the Japanese knotweed infestation before a fire is lit [1]. It’s important that you do not further spread the plant in the process of isolating it.

Once all the material has been collected it can be burned privately, although you should check with your local council before doing so. Once the fire has burned out it is likely that crowns and rhizomes will still remain active, these should then be buried as described earlier, or removed by a registered waste carrier to a licensed disposal site.

If you’re a farmer, or a business owner, then you need to tell the Environment Agency at least a week in advance, as well as your local council environmental health officer.

Using Tarps to Smother Japanese Knotweed

You’ll need:

  • A saw, secateurs or shears
  • Gardening gloves
  • Tarpaulin, old carpet or root barrier membrane
  • Heavy rocks, pegs or posts
  1. Isolate the area affected by Japanese knotweed and mark it clearly.
  2. Use a sharp saw, secateur or shears to cut down any growth above ground.
  3. Saw down any cut stumps to make the ground as level as possible.
  4. Set aside any Japanese knotweed cuttings for safe disposal later.
  5. Spread your tarpaulin or root barrier membrane over the affected area.
  6. Pin down the tarpaulin with heavy rocks or use posts or pegs to secure the covering.
  7. Cover the entire area with top soil to prevent any light coming through.
  8. Observe over the next few years and treat any rogue shoots with glyphosate herbicide solution.

Tips for Removing Japanese Knotweed

How do you control knotweed?

Controlling Japanese knotweed involves taking steps to limit its growth in the long term, making it more manageable for a property owner who is not planning on selling up soon. Japanese knotweed will inevitably spread if left unchecked, therefore it does need to be controlled if you have discovered it on your land.

Controlling is a good option for landowners who have discovered an infestation that is more than 7 metres from any building [6] and have the resources to commit to a long-term plan. Methods to control Japanese knotweed include cutting down and treating with glyphosate treatment, or covering with tarpaulin.

Is it illegal to remove Japanese knotweed?

You are legally required to keep any invasive plants on your land under control, this includes Japanese knotweed. As the plant is labelled as controlled waste by the Wildlife and Countryside Act 1981 [7], it is illegal to simply remove Japanese knotweed from your land and dump it elsewhere. Doing so is one and the same as fly-tipping, with the added offence of spreading an invasive plant into the wild. If you are caught dumping any Japanese knotweed matter or soil contaminated with the plant you could face a large fine or even prison time.

Where can I dispose of Japanese knotweed?

If you wish to legally remove your Japanese knotweed and bury it elsewhere you will likely need the assistance of a treatment specialist. PCA-accredited Japanese knotweed specialists have access to the equipment, vehicles and contacts in order to legally complete the job effectively and within the limits of the law.

You are permitted to supervise the removal of your Japanese knotweed infestation, but you must use a registered waste carrier to remove the plant from your land [1]. You are only allowed to bury knotweed at authorised landfill sites, you are also required to call in advance to give them time to prepare.

How long does it take to get rid of Japanese knotweed?

The time it takes to get rid of Japanese knotweed depends on the size of the infestation and the techniques used to combat it. Most professional treatment firms will offer a 5-year insurance backed certificate which guarantees that they will return to treat the plant for the stipulated time. Most domestic Japanese knotweed infestations can be expected to be killed within this time frame, however larger problems may take longer to get under control.

Can I treat Japanese knotweed myself?

You can treat Japanese knotweed yourself with shop-bought chemical treatments containing glyphosate to treat small infestations [1]. However, treating knotweed yourself is not advised as the process is time consuming and there is also no guarantee that you’ll be able to complete the job.

You will also be unable to obtain a PCA-accredited certificate, which will lead to further difficulties should you wish to sell the affected property, or if a neighbour is threatening litigation from the spread of knotweed from your property. DIY treatments take a long time to take effect and may end up costing you more money in the long term.

Can Japanese knotweed come back?

Japanese knotweed usually comes back after the first two or three herbicidal treatments, depending on the chemicals used and the time of year the treatment is done. Once treated, the Japanese knotweed comes back the following years in a smaller, bushier form – usually no taller than 90cm. This regrowth should be treated in the same way to keep the plant in remission.

Attempting a DIY solution, like those featured above, can easily backfire and you may end up worsening the infestation. A professional treatment plan ensures that a team returns to treat the infestation for several seasons, so that any remnant of the plant is properly eradicated.

When is the best time to remove Japanese Knotweed?

The best time to remove Japanese knotweed is during the spring. At this time of year, Japanese knotweed starts shooting through the ground [3], a perfect opportunity to smother with root barrier membranes, with a view to digging out and removing at a later date.

Whereas during the summer, when growth is at its peak, it is more practical to apply a herbicide treatment [4], so that the infestation can be easily removed the following year.

Excavating and burying Japanese knotweed can be done at any time of the year with mechanical aid and a PCA-accredited removal firm. Such a firm will abide by the PCA’s Code of Practice [5] which should ensure effective treatment.

How much does it cost to get rid of Japanese knotweed?

It costs approximately £3,000 to get rid of Japanese knotweed from a typical residential property using a herbicidal treatment plan that is insurance backed by the PCA. The exact cost of getting rid of Japanese knotweed will depend on the size of the infestation, the method used and the time estimated for completion.

For example, an expert Japanese knotweed removal company who suggests that a combination of treatment methods should be used in order to effectively remove the plant for good, may charge more than another firm who decides to just use herbicidal treatments.

Any work that requires large-scale excavation and removal of Japanese knotweed contaminated soil will cost more than chemical treatment, as this kind of work requires the use of heavy machinery. Japanese knotweed removals of this nature can start at £7,000 but may prove more expensive depending on environmental factors such as geology, access to the site and topography.

How should you choose a Japanese knotweed removal service?

You should choose a Japanese knotweed removal service that is accredited by the Property Care Association (PCA). Ask any prospective contractors if they are accredited and check with the PCA to make sure this is the case.

Only PCA-accredited Japanese knotweed removal firms can offer an insurance-backed guarantee with their work. Without this guarantee, many mortgage lenders will not deal with properties that are affected by Japanese knotweed, even if the plant has been properly removed.

Basic reputation and credential checks can help cut the wheat from the chaff. Check online reviews, find testimonials of the business from third-party websites if possible and compare estimates to ensure that you’re getting the best value for money. Ensure that you have written confirmation of the work to be completed from the firm before starting so that both parties are clear of the expectations.

How difficult is it to get rid of Japanese knotweed?

Japanese knotweed is a difficult plant to get rid of, especially if professional help isn’t sought out. The plant can grow quickly through the summer and reach a height of over 2m. The rhizome root structure that sustains the vegetation above ground can spread 2m deep and is capable of regenerating into complete plants from small fragments, whenever it comes into contact with soil and water.

Whether using conventional herbicide treatments or digging out the plant using machinery, those undertaking the removal must take extreme care in order to not accidentally spread the plant further throughout the course of the treatment. Treatments must also be followed up with inspections in the following years, to ensure that it has been effective and to nip any resurgent shoots in the bud.

How do I permanently get rid of Japanese knotweed?

Permanently get rid of Japanese knotweed by hiring a PCA-accredited removal service to deal with the infestation. Taking a DIY approach to removing Japanese knotweed can result in partial effectiveness and may lead to the plant returning year after year. A professional Japanese knotweed removal service will have access to industrial chemicals that are also likely to prove much more effective in permanently getting rid of the problem.

Do you need a license to remove Japanese knotweed?

You need to use a registered waste carrier to remove Japanese knotweed from any site. Any contaminated soil must be taken to an authorised landfill site in order to be legally disposed of. It’s not possible to get a waste licensing exemption for the disposal of Japanese knotweed.

How can you get rid of Japanese knotweed organically?

Get rid of Japanese knotweed organically by either digging it up, burning it or smothering it with a tarpaulin. All these methods do not require the use of any herbicides that could potentially damage nearby plants, however, they each have their drawbacks.

Digging up a Japanese knotweed infestation is organic, but is by the most costly method. If you choose to burn the Japanese knotweed you run the risk of not burning every last fragment and risk a resurgence. Meanwhile, smothering Japanese knotweed can take much longer to prove effective.

Are You Sure It’s Japanese Knotweed?

Making a positive identification of Japanese knotweed is crucial before considering investing time or money into any removal process. This plant has a number of key identifying features including broad, shield-shaped green leaves and hollow, bamboo-like canes [2]. Unfortunately, there are a number of other weeds and plants that could be easily confused for Japanese knotweed, so it’s advisable to check with an expert before you spend money on any equipment or professional removal service.

Just discovered Japanese knotweed?

Whether you’ve just discovered knotweed on your land or have a long-term infestation, we can help explain your options and may be able to help you claim for the costs of treatment. If it has entered your land from another property, or you’ve just bought a house with Japanese knotweed then you could be able to get the costs of the treatment recovered.

Getting your Japanese knotweed problem treated professionally effectively hits two birds with one stone. Our specialists will be able to assess your infestation and lay out a clear strategy to tackle it, as well as offer you an insurance backed guarantee so that banks and lenders will feel comfortable dealing with you. Which form of treatment that you’ll be offered will depend on the severity of your infestation and also the nature of your property.

Call us today on 0151 242 9050 or send us an enquiry using the contact form on the right to see if we can help you with your knotweed problem.

References

[1] Prevent Japanese knotweed from spreading – Gov.uk https://www.gov.uk/guidance/prevent-japanese-knotweed-from-spreading

[2] Japanese knotweed Profile – RHS – https://www.rhs.org.uk/advice/profile?pid=218

[3] Japanese Knotweed Life Cycle & Ecology – University of Leicester – https://www2.le.ac.uk/departments/genetics/people/bailey/res/life

[4] When is the best time to control Japanese knotweed? – University of New Hampshire – https://extension.unh.edu/blog/when-best-time-control-japanese-knotweed

[5] Code of Practice Management of Japanese knotweed – PCA – https://www.property-care.org/wp-content/uploads/2020/02/PCA-COP-Control-of-Japanese-Knotweed_WEB-1.pdf

[6] Japanese Knotweed and residential property – RICS – https://www.rics.org/globalassets/rics-website/media/upholding-professional-standards/sector-standards/real-estate/japanese-knotweed-and-residential-property-1st-edition.pdf

[7] Wildlife and Countryside Act 198 – Gov.uk – https://www.legislation.gov.uk/ukpga/1981/69

[8] INNSA Standard Burial Of Japanese Knotweed – INNSA – https://www.innsa.org/standarts/innsa-standard-burial-of-japanese-knotweed/

[9] Stop invasive non-native plants from spreading – Gov.uk – https://www.gov.uk/guidance/prevent-the-spread-of-harmful-invasive-and-non-native-plants

[10] Managing Japanese Knotweed and Giant Knotweed on Roadsides – Penn State University – https://plantscience.psu.edu/research/projects/vegetative-management/publications/roadside-vegetative-mangement-factsheets/5managing-knotweed-on-roadsides

[11] Effect of soil contaminated by diesel oil on the germination of seeds and the growth of Schinus terebinthifolius Raddi (Anacardiaceae) – Seedlings – Brazilian Archives of Biology and Technology – http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-89132011000600025

Paolo Martini

Paolo Martini is the lead solicitor for Knotweed Help and has over 30 years of experience in the field of Civil Litigation and is an expert on the legal issues faced by individuals dealing with Japanese knotweed on their land. Now considered one of the country's leading litigators in Japanese knotweed law he works alongside the country’s top barristers and experts. His in-depth legal experience and connections to the Japanese knotweed removal industry make him uniquely suited for handling your case.