Environment Agency
Japanese knotweed is the most common of 4 invasive knotweed plant species in the UK.
These are:
- 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:
- roadsides
- waste ground
- railway embankments and cuttings
- spoil tips that are made up of waste material from mining or quarrying
Its also commonly found along rivers and streams.
How knotweed spreads
Knotweed spreads through:
- direct rhizome (root) growth
- new plant growth from the parent plants 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 its 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.
Youll 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:
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).
Bury it
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 theyre 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:
- undamaged
- 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 theyre part of an assurance scheme, such as one with a relevant trade body.
Burn it
If youre 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 youre 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 youre 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 its got a permit to accept material containing invasive plants the waste site may also need time to prepare
- tell the waste site that youre 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