How To Get Rid Of Japanese Knotweed

By Paolo Martini on 2nd July 2019 (updated: 6th October 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.

Identifying 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.

When to Remove Japanese Knotweed

Removing Japanese knotweed is a challenge at any time of year, however certain seasons do lend themselves to specific removal solutions. During the spring, knotweed starts shooting through the ground [3] making this a perfect time 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.

What You’ll Need to Remove Japanese Knotweed

For smothering Japanese knotweed:

  • A saw, secateurs or shears
  • Gardening gloves
  • Tarpaulin, old carpet or root barrier membrane
  • Heavy rocks, pegs or posts

For cutting Japanese knotweed

  • A saw, secateurs or shears
  • A container or sack to hold cuttings

For digging up Japanese knotweed

  • A micro digger or similar vehicle
  • A skip or licensed waste removal van

For using herbicide

  • 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

For burying Japanese knotweed

  • A micro digger or similar vehicle
  • Tarpaulin, old carpet or root barrier membrane

Instructions

Using Tarps to Smother Japanese Knotweed

  1. Isolate the area affected by Japanese knotweed and mark it clearly.
  2. Use a sharp saw, secateurs 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. Spead 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 topsoil to prevent any light coming through.
  8. Observe over the next few years and treat any rogue shoots with glyphosate herbicide solution.

Cutting Japanese Knotweed

  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.

Digging up Japanese Knotweed

  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.

Using Herbicide to Kill Japanese Knotweed

  1. If using a foliar sprayer, isolate the area and remove any plants or vegetation that you do not want to be 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.

Burying Japanese Knotweed

  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.

Burning Japanese knotweed

  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.

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.

Why 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].

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.

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.

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 do you 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.

Will vinegar kill Japanese knotweed?

There is no scientifically backed evidence to suggest that vinegar will kill Japanese knotweed. Although there has been some student research [11] 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 a 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 [12] 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.

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.

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.

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. 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 can come back if you fail to properly treat it properly the first time. 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.

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

[2] Japanese knotweed Profile – RHS

[3] Japanese Knotweed Life Cycle & Ecology – University of Leicester

[4] When is the best time to control Japanese knotweed? – University of New Hampshire

[5] Code of Practice Management of Japanese knotweed – PCA

[6] Japanese Knotweed and residential property – RICS

[7] Wildlife and Countryside Act 198 – Gov.uk

[8] INNSA Standard Burial Of Japanese Knotweed – INNSA

[9] Stop invasive non-native plants from spreading – Gov.uk

[10] Managing Japanese Knotweed and Giant Knotweed on Roadsides – Penn State University

[11] Senior Science Project: How to kill Japanese Knotweed

[12] 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

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.