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How to deal with Japanese knotweed

Got Japanese knotweed growing on your property? Don’t panic. From burying it to burning it, it’s possible to purge the plant permanently as long as you take the right steps.

Got Japanese knotweed growing on your property? Don’t panic. From burying it to burning it, it’s possible to purge the plant permanently as long as you take the right steps.

Written by
Anna McEntee
Insurance comparison expert
Reviewed by
Kate Hughes
Insurance expert
13 APRIL 2022
5 min read
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What is Japanese knotweed? 

Japanese knotweed (Fallopia japonica) is a fast-growing plant that can reach up to two metres high. It was originally introduced to Britain as an ornamental garden plant, but its ability to grow and spread rapidly means it can take over your garden. Worse, its roots can potentially damage drains, paving, walls and even foundations. 

Having knotweed on a property can be a problem if you’re trying to buy or sell a home as it can put off mortgage providers from lending on the property. Read more to discover how you can deal with your Japanese knotweed.

Can I deal with Japanese knotweed myself? 

If you only have a small amount of Japanese knotweed, you might be able to deal with it yourself. But if it’s a large amount, it’s advisable to get the professionals in. They can also give you a guarantee that it’s been successfully eradicated, which should be acceptable to mortgage providers. 

Do your research and ask around to find the best contractor. When choosing a professional, the government advises looking for a contractor with one of these accreditations and registrations: 

  • Amenity Forum Membership
  • BASIS Professional Register
  • BASIS Amenity Training Register
  • BASIS Nominated Storekeeper (NSK) Professional Register.

Can you dig out Japanese knotweed?

You can dig out Japanese knotweed, but it isn’t the best way of completely removing it. The roots of the plant regenerate very quickly – if you dig out the knotweed but end up leaving some deep roots in the ground (by accident or because you or a professional are unable to get them out), this will cause the plant to grow again. 

If you succeed in digging out the entire plant, you need to dispose of it at a licensed landfill site as Japanese knotweed is legally classed as ‘controlled waste’. If you want to get a professional to dig out the knotweed, you must make sure they’re registered waste carriers. 

Don’t forget – Japanese knotweed should never be included with normal household waste or put in a green waste collection bin.

Can you kill Japanese knotweed? 

You can kill small amounts of Japanese knotweed by using weedkiller, but it usually takes up to three or four seasons to do so. 

A glyphosate-based weedkiller will be one of the most effective in killing knotweed. Spray it onto the leaves or cut stems. The knotweed will produce smaller regrowth the following spring, and you should then spray again until the plant dies.

Can you burn Japanese knotweed? 

Yes, but it will only work if all the plant’s strands are completely dry. When this is the case there’s less risk of the plant regrowing and a higher chance that it will all burn.

If you’re an individual who wants to burn Japanese knotweed, you first need to check with your local council that burning is allowed. 

Businesses that want to burn knotweed must: 

  • Tell the Environment Agency at least a week before they burn it
  • Tell the environmental health officer at your local council
  • Get a burning waste in the open exemption
  • Make sure they follow local byelaws

Is it okay to bury Japanese knotweed? 

You can get rid of the dead brown canes of Japanese knotweed by burying them on site, but you must notify the Environment Agency at least one month before you do this. 

The dead canes must be cut, not pulled, a minimum of 10cm above the crown. You must then bury on the same site. If you have sealed the dead canes with a material called a geotextile membrane, you should bury it at least two metres. If you haven’t sealed it, you should bury it at least five metres down.

How much does it cost to remove Japanese knotweed? 

On average, it can cost between £1,000-£4,000 to remove Japanese knotweed, but this can be higher depending on the size of the area that has to be cleared and the removal method you choose. 

Keep in mind that professionals may charge different rates, so costs can vary.

How to cheaply remove Japanese knotweed 

If you want a cheap way to remove Japanese knotweed, you could try a weedkiller. You can buy a glyphosate-based weedkiller for less than £30 online or in store. Other methods of removal may involve you having to pay a professional.

How to stop Japanese knotweed from spreading in your garden 

Japanese knotweed spreads through rhizome (root) growth or new plant growth from the parent plant’s stem and rhizome fragments – ones as small as 1cm.

To stop it from spreading in your garden, you can spray or inject the stems with approved herbicides. But, if you’re using chemicals, you might need to: 

  • Make sure whoever is spraying the chemical holds a certificate of competence for herbicide use or works under direct supervision of someone who has a certificate
  • Carry out a Control of Substances Hazardous to Health assessment
  • Get permission from Natural England if the garden is in a protected area
  •  Get permission from the Environment Agency if the plants are near water

Permanent removal for Japanese knotweed 

You should be able to permanently remove all Japanese knotweed if you follow relevant steps and advice when using a glyphosate-based weedkiller, burning or burying the Japanese knotweed or digging it. Contracting someone to do the job can also increase the chance that all Japanese knotweed will be permanently removed.

Frequently asked questions

Do I legally have to remove any Japanese knotweed on my property?

You don’t legally have to remove Japanese knotweed from your land unless it’s causing a nuisance. But if it spreads from your property you could be prosecuted.

What do I do if my neighbours property has Japanese knotweed?

If you spot that your neighbour has Japanese knotweed, you should tell them as soon as possible. If they know and they don’t stop it from entering your garden, you might be able to sue them for damages and the cost of removing the knotweed.

Is Japanese knotweed harmful?

Although it causes damage to properties, Japanese knotweed is not harmful to humans. It isn’t poisonous, doesn’t cause burns or skin irritation and is safe to touch and pick.

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