Japanese knotweed advice

Japanese Knotweed FAQs

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.

To skip straight to our "Dos and Don'ts" of Japanese knotweed, click here.

How does Japanese knotweed spread?

Japanese knotweed spreads as a result of the plants' above ground stems or rhizome (underground vegetative stem matter/roots) being moved and spread around. Only the female form of the plant is present in the UK and it 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 (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, here.

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?

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.

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.
  • Isolate the Japanese knotweed by means of ‘7m rhizome spread fencing’ prior to the commencement of development works to prevent any disturbance of the plant by workers, vehicles or members of the public.
  • 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. Treatment of Japanese knotweed on land banks is highly recommended as they will prove easier to either sell or develop than if the knotweed has been allowed to thrive for several years.
  • Adhere to recommendations in the Environment Agency Knotweed Code of Practice (2013 version 3), when managing and treating Japanese knotweed.

Don't

  • Where possible allow works to commence on a development site without first drawing up a Knotweed Management Plan (KMP).
  • Allow demolition contractors or ground workers to conduct a site scrape or demolition on a site until the site has been properly inspected for the presence of knotweed.
  • Allow knotweed material to intentionally or unintentionally leave your site in a manner that will contravene the Environmental Protection Act and the Environmental Protection (Duty of Care) Regulations. If Japanese knotweed material is to leave site it must do so via a registered waste carrier and must be disposed of by prior arrangement at a specially licensed landfill facility able to accept and dispose of Japanese knotweed.
  • Allow Japanese knotweed to spread into adjacent properties, as this will contravene The Wildlife and Countryside Act and leave 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 and have to be disposed of accordingly.
  • 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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