Japanese knotweed advice

Japanese Knotweed FAQs

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The presence of Japanese knotweed can cause disruption to development projects and incur unbudgeted costs through treatment and site delays if not dealt with properly from the very start.

There are plenty of myths about Japanese knotweed such as you have to notify your local council, it can burn you, it's poisonous and your house will be destroyed by it. The questions here represent what we're most commonly asked.

If you have a question that's not answered here, please contact us.

Skip straight to our Dos and Don'ts of Japanese knotweed.

Can you Get Rid of Japanese Knotweed?

Whilst the internet provides a plethora of solutions for getting rid of Japanese knotweed, there are only two methods of dealing with knotweed; herbicide treatment or excavation. Find out more about the methods to get rid of Japanese knotweed.

How Does Japanese Knotweed Spread?

Japanese knotweed spreads as a result of the plants' stems, or rhizomes (underground roots) being moved and spread around. Only the female form of the plant is present in the UK and therefore, it cannot pollinate and produce any viable seed, other than hybridising with other similar knotweed species. Trials have shown as little as 0.7 grams of rhizome material, which is smaller than your little finger nail can produce a new plant within 10 days. Find out more about Japanese knotweed, how it came to the UK and how it grows, on our page What is Japanese Knotweed?.

Is Japanese Knotweed Notifiable/Reportable?

No you are not obliged to report Japanese knotweed on your premises to the authorities. Find out more about Japanese Knotweed & the Law, here.

Is Japanese Knotweed Poisonous, Can it Cause Burns?

No, Japanese knotweed is not poisonous and does not cause burns. Some people get the name confused with Giant hogweed, which can cause burns or Common ragwort, which is poisonous. Both of these are also non-native invasive weeds.

Is Japanese Knotweed Edible?

Yes Japanese knotweed shoots are edible but we do not recommend harvesting it due to its invasive nature and the risk of spreading which can lead to criminal prosecution. Note that it is illegal to transport Japanese knotweed from source without a Waste Carrier Licence.

Can I Burn Japanese Knotweed?

You can but you must do this with extreme care. When the knotweed material has been excavated, cut the stems and leaves and leave it to dry before burning it, ideally without contact with the soil. The knotweed material must be burnt on site and not be burnt anywhere else as you could potentially carry a fine and in extreme cases, a custodial sentence. Bear in mind though, in its native area, Japanese knotweed grows on volcanic ash and around hot fumaroles. Check the local byelaws with regards burning/bonfires.

Can I get a Mortgage on my Property when it has Japanese Knotweed?

This very much depends on the mortgage lender. Always check with them first. For most mortgage lenders they are happy to lend as long as there is a professional company in place to control the knotweed infestation. Make sure you instruct a reputable contractor like Japanese Knotweed Ltd who are Property Care Association accredited and can document all work being done. Find out more about Japanese knotweed and mortgages.

Are the Herbicides used to Treat Japanese Knotweed Harmful to my Children or Pets?

No. The herbicides we use are completely safe to your children and pets. The herbicide we use is safe when wet, but for precaution, we advise that pets and children are kept out of the treated area for approximately 1-2 hours following application, until the herbicide has dried.

Can I put Japanese Knotweed in my Garden Bin?

No, this would be illegal. Japanese knotweed is classed as “controlled waste” and needs to be cut down carefully and either burnt on site or taken away to a licensed landfill site or incineration facility. You can use a Knotweed Disposal Bag to dispose of knotweed waste. Find out more about the Knotweed Bag here.

Can I Cut or Mow Japanese Knotweed?

Yes but you must keep the knotweed waste on site or dispose of it at a licensed landfill. You can purchase a Knotweed Bag to dispose of your knotweed waste. Find out more about the Knotweed Bag here. Clean the mower before mowing other parts of the garden.

Can I add Japanese Knotweed to Compost?

No as this could lead to knotweed taking root growing in your compost heap.

Can Japanese Knotweed Spread from its Leaves?

No it can't. Whilst the leaves drop off in the autumn/winter, they should not cause concern regarding the plant's spread.

Can Japanese knotweed be Killed?

Find out more about killing Japanese knotweed here.

Whether you encounter knotweed on a major building project or as part of a maintenance scheme, please ensure you follow these basic guidelines:

Do

  • Contact Japanese Knotweed Ltd so we can manage, control and remove the problem for you.
  • Fence the Japanese knotweed off if there is an imminent risk of disturbance. Fencing should be erected 5-7 metres away from the visible growth to prevent disturbance of the plants’ underground rhizome. It should be clearly signed.
  • Draw up a Knotweed Management Plan - especially if a number of contractors are to be involved on the site and adhere to it throughout your project.
  • Commence treatment/removal of Japanese knotweed as soon as possible after discovering its presence.
  • Adhere to recommendations in the PCA Code of Practice for managing knotweed, when controlling or removing Japanese knotweed.

Don't

  • Where possible allow works to commence on a development site without first drawing up a Knotweed Management Plan (KMP).
  • Allow contractors to undertake site work until the site has been properly surveyed for the presence of knotweed.
  • Allow knotweed material to leave your site intentionally or unintentionally in a manner that will contravene the Environmental Protection Act and the Environmental Protection (Duty of Care) Regulations.
  • Allow Japanese knotweed to spread into adjacent properties, as this could contravene legislation and private nuisance laws leaving you vulnerable to third party litigation from your neighbour(s).
  • Flail or strim knotweed, as this will cause the Japanese knotweed to spread.
  • Store materials on top of Japanese knotweed areas, or the materials themselves could become contaminated with knotweed.
  • Chip Japanese knotweed material, as mechanical chippers do not kill the plant and could result in new Japanese knotweed growth wherever the chipped material is spread.
  • Add Japanese knotweed to compost, as this can lead to knotweed growing in your compost heap.
  • Burn Japanese knotweed as a sole means of treatment as large rhizome and crowns can survive burning.

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