Japanese knotweed is the most common of 4 invasive knotweed plant species in the UK.
- Japanese knotweed
- Dwarf knotweed
- Giant knotweed
- Bohemian (hybrid) knotweed
How to identify Japanese knotweed
See a description and photographs of Japanese knotweed on the Non-native Species Secretariat website.
Where knotweed grows
Knotweed can grow in most soil conditions found in the UK, particularly in man-made habitats, such as:
- waste ground
- railway embankments and cuttings
- spoil tips that are made up of waste material from mining or quarrying
It’s also commonly found along rivers and streams.
How knotweed spreads
Knotweed spreads through:
- direct rhizome (root) growth
- new plant growth from the parent plant’s stem and rhizome fragments – a new plant can grow from pieces of rhizome as small as 1cm
If you have knotweed on your land or property
You must stop Japanese knotweed on your land from spreading off your property. Soil or plant material contaminated with non-native and invasive plants like Japanese knotweed can cause ecological damage and may be classified as controlled waste.
You do not legally have to remove Japanese knotweed from your land unless it’s causing a nuisance, but you can be prosecuted for causing it to spread into the wild.
How to stop knotweed spreading
Do not treat knotweed yourself unless you have the appropriate skills and experience. You can find companies that specialise in treating knotweed.
Spray with chemicals
Spraying or injecting the stems with chemicals can be an effective treatment to stop knotweeds spreading. You must only use approved herbicides.
You’ll have to respray. It usually takes at least 3 years to treat Japanese knotweed. Knotweed rhizome can remain dormant in the soil for many years and will regrow if disturbed or if the soil is relocated.
When using chemicals, you may need to:
- make sure anyone spraying holds a certificate of competence for herbicide use or works under direct supervision of a certificate holder
- carry out a Control of Substances Hazardous to Health assessment
- get permission from Natural England if the area is protected, for example sites of special scientific interest
- get permission from the Environment Agency if the plants are near water
To dispose of certain chemicals, you may need:
- an environmental permit
- a waste exemption
- trade effluent consent
You must dispose of chemicals through a registered waste carrier to a permitted waste disposal facility.
Find out how to treat and dispose of invasive non-native plants (RPS 178).
You must notify the Environment Agency at least one month before you bury the knotweed.
You can dispose of the dead brown canes of Japanese knotweed by composting on site, as long as they’re cut (not pulled) a minimum of 10cm above the crown.
You must bury knotweed material:
- on the site it came from, including ash and soils containing potential knotweed propagules
- at a depth of at least 5 metres, if you have not sealed with a material called a geotextile membrane
- at a depth of at least 2 metres, if you have sealed with a geotextile membrane
You must make sure that any geotextile membranes used for burial are:
- large enough to minimise the need for seals
- sealed securely
- will remain intact for 50 years
- UV resistant
You can use a contractor with experience burying knotweed. Check that they’re part of an assurance scheme, such as one with a relevant trade body.
If you’re a business that wants to burn Japanese knotweed, you must:
- tell the Environment Agency at least a week before you burn it
- tell the environmental health officer at your local council
- get a burning waste in the open exemption (a D7 exemption)
- follow local byelaws and not cause a nuisance
If you’re an individual who wants to burn Japanese knotweed, you only need to check with your local council that burning is allowed.
Knotweed crowns and rhizomes may survive burning, so you must follow the guidance for how to bury it or how to dispose of it off site.
Companies that specialise in treating knotweed
You can supervise the management and disposal of knotweed yourself, or you can hire a specialist to do it for you.
Look for a contractor with the following accreditations and registrations:
- Amenity Forum Membership
- BASIS Professional Register
- BASIS Amenity Training Register
- BASIS Nominated Storekeeper (NSK) Professional Register
Many of these companies belong to one of these trade bodies:
How to dispose of Japanese knotweed off site
If you cannot dispose of Japanese knotweed suitably on site, you must send it to a landfill site or incineration facility that has the correct type of permit.
To find out where you can send it, contact the Environment Agency or your local waste disposal site. You must tell the Environment Agency that you have done this and where you have sent it.
You must use a registered waste carrier and an authorised landfill site or suitable disposal site.
You must follow the law if you have been employed to transfer goods or material by road and you’re disposing of any waste that has or might have Japanese knotweed in it.
You must not:
- dispose of Japanese knotweed with other surplus soil
- sell soil contaminated with Japanese knotweed as topsoil
You can only reuse soils contaminated with knotweed after treatment on the site where they were growing.
You cannot get a waste licensing exemption for the use of Japanese knotweed.
Before you transfer Japanese knotweed waste, you must:
- check with the waste site in advance to make sure it’s got a permit to accept material containing invasive plants – the waste site may also need time to prepare
- tell the waste site that you’re transferring Japanese knotweed waste
- operate within the conditions in treatment and disposal of invasive non-native plants: RPS 178
- get an environmental permit to transport and dispose of controlled waste
When you transfer the Japanese knotweed waste, you must cover or enclose it in the vehicle so that no waste can escape during your journey.
After you transfer Japanese knotweed waste
After you have transferred the Japanese knotweed waste at the disposal site, you must:
- brush vehicles down vigorously or jet-wash them to clear them of any Japanese knotweed
- inspect your vehicles to check there are no trapped pieces of plant or rhizome
You can contact the Environment Agency for help if you:
- have more questions about how to handle waste containing Japanese knotweed
- want to find out more about when you need a licence to dispose of Japanese knotweed
- want to complain about waste producers who are not telling people they employ how to transfer Japanese knotweed – this is breaking the rules on their waste duty of care
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Published 30 March 2016
Last updated 17 February 2023 +show all updates
Added a section on how to identify Japanese knotweed with a link to photographs. Added links to guidance for Scotland, Wales and Northern Ireland.
Tier 2 changes as part of the content improvement project. Includes changes to headings and overall content review.
New links to the Invasive non-native specialists association, Property Care Association and RPS 178: treatment and disposal of invasive non-native plants.
Clarified that the Environment Agency are not responsible for dealing with Japanese Knotweed. You can contact them for guidance, but it is the responsibility of the landowner to deal with Japanese knotweed.
Any business wanting to burn Japanese Knotweed waste must register for a waste exemption (if they can meet the conditions) and notify their local EPR waste team at least a week before they intend to carry out the burning. This applies to all businesses, including farmers.
Spray with chemicals
Spraying or injecting the stems with chemicals can be an effective treatment to stop knotweeds spreading. You must only use approved herbicides. You'll have to respray. It usually takes at least 3 years to treat Japanese knotweed.
The best approach to control is through a combination of cutting and herbicide application. A late spring/early summer treatment followed by an early fall re-treatment is needed. Several years of treatment may be needed for well-established populations.How do you keep knotweed from growing? ›
Japanese knotweed is best controlled by the application of a suitable herbicide. Glyphosate-based herbicides are commonly used to treat Japanese knotweed. If glyphosate is applied correctly, at the appropriate time of year, it is possible to eradicate it, although it can take two to three years of repeated treatment.What can outcompete Japanese knotweed? ›
Switchgrass was chosen in the hope that its deep and extensive root system (reaching 9 feet deep or more) could compete with that of knotweed, and that the density of above-ground growth might shade out knotweed sprouts.Does mowing spread Japanese knotweed? ›
Mowing/Cutting can result in the spread of Japanese knotweed under certain conditions. Mowed/cut stems/fragments with nodes/joints have the ability to develop adventitious roots and shoots if they come in contact with moist soils or water.Why is it so hard to get rid of Japanese knotweed? ›
Due to the powerful root and rhizome system, which extends deep into the ground, knotweed is notoriously difficult to treat or remove without professional help – and failure to do so could result in your property being damaged and devalued.What is the cheapest way to get rid of Japanese knotweed? ›
The cheapest way to deal with a Japanese knotweed infestation is with herbicide treatment. However, this is generally recognised as being a 'control' rather than a one-off solution, because there's a risk of dormancy and regrowth, especially on land that's disturbed.How do you get rid of Japanese knotweed naturally? ›
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.Is it easy to get rid of knotweed? ›
It is very recognisable as a tall herbaceous plant. It can grow 3m a year and it's underground rhizomes can spread 7m across and penetrate anywhere from 2 to 7m deep. This clearly makes the plant almost impossible to eradicate. Tall red stems grow at a rapid rate and produce large heart shaped leaves with flat base.What kills knotweed? ›
Glyphosate is the herbicide of choice for controlling knotweed.
Cut Down and Remove the Canes
One method is to use sharp pruning shears or loppers to take down the stems as close to the ground as possible, making sure to remove every last cut piece and fragment because as little as half an inch of the root or cut stem can grow into another plant.
How the imported insects control Japanese knotweed. The imported insects, aphalara itadori, control Japanese knotweed by sucking out the sap from the stem which causes the invasive weed to dry out. The insect does not feed on anything else other than Japanese knotweed and is therefore entirely dependent on the weed.Is there anything good about Japanese knotweed? ›
Herbalists use Japanese knotweed to reduce plaque, gum pain, and gingivitis, claiming it has anti-inflammatory properties. Additionally, emodin is a natural compound in Japanese knotweed roots that serves as a natural laxative.What is the best Japanese knotweed killer? ›
Roundup, Gallup, Landmaster, Pondmaster, Ranger, Rodeo, and Touchdown are all herbicides recommended to kill Japanese Knotweed. They are all glyphosate-based herbicides and will kill the troublesome weed. The best time to spray the leaves of Japanese Knotweed with herbicide is late summer or early autumn.What plants fight knotweed? ›
The riparian buffer and prairie cordgrass – Virginia wildrye mixtures were most competitive with Japanese knotweed. Figure 8. The 2008 planting of prairie cordgrass and Virginia wildrye, shows promise to control Japanese knotweed.What happens if you touch knotweed? ›
Japanese knotweed is not poisonous and is not harmful to touch, however, always use caution to avoid inadvertently allowing the infestation to spread.How deep do Japanese knotweed roots go? ›
Japanese Knotweed is a resilient and tough weed. It has roots that can grow to a depth of 2 meters. These roots are known as rhizomes – they're a special sort of root that is also a 'shoot'. These stretch out horizontally and can extend up to 7 meters wide.How far down do Japanese knotweed roots go? ›
The roots of Japanese knotweed can grow 1m deep, making them extremely difficult to dig out, and the plant can grow through cracks in brickwork and pipework. It is against the law to allow Japanese knotweed on your land to spread onto other people's property or into the wild.What eats Japanese knotweed? ›
Psyllids feed on the sap of the knotweed, diminishing its energy supply and ultimately killing the plant. Researchers found that the Japanese knotweed psyllid's preference is specific to the three targeted knotweeds, and it is not expected to damage any native or related knotweed family plants.Can Japanese knotweed grow through concrete? ›
The simple, and definitive, answer to the question of "can Japanese knotweed grow through concrete?" is no, it cannot. No matter how virulent this weed is, it does not have the force to break through brick or concrete.
Why is Japanese knotweed a problem? Over many years, Japanese knotweed has acquired a reputation as one of the most invasive plants, and has been blamed for causing damage to properties. This, combined with its zombie-like refusal to die, has made it into a big green bogeyman for the housing industry.Who is responsible for Japanese knotweed? ›
Japanese Knotweed is classified as an invasive species it is therefore the responsibility of the land owner to prevent the plant spreading to neighbouring land (or into the wild), and removal of plant must be conducted with due care and attention.How much does Japanese knotweed devalue a house? ›
Japanese Knotweed can devalue a property between 5 and 100%. There have been cases where homes have been completely devalued as a result of severe infestations, however, these are rare occurrences currently.How far away should Japanese knotweed be? ›
As long as the knotweed is at a distance of 7m or more from your house, you should have no cause to worry. An appropriate herbicide programme will deal with this threat quite effectively. Even if the knotweed falls within the 7m zone, this should not preclude the sale of the property.What happens if you touch Japanese knotweed? ›
Japanese knotweed is not poisonous and is not harmful to touch, however, always use caution to avoid inadvertently allowing the infestation to spread.How far do Japanese knotweed roots spread? ›
At its most prolific, Japanese Knotweed can grow up to 20cm per day. The roots can grow 3 metres deep into the ground and spreads 7 metres in all directions, which can lead to structural problems within properties.How deep are the roots of Japanese knotweed? ›
Japanese Knotweed is a resilient and tough weed. It has roots that can grow to a depth of 2 meters. These roots are known as rhizomes – they're a special sort of root that is also a 'shoot'. These stretch out horizontally and can extend up to 7 meters wide.