3 Of The Best Methods For Treating Japanese Knotweed.

warning Japanese knotweed sign

What Is Japanese Knotweed?

Japanese Knotweed is a perennial non-native invasive species of plant, that was brought over from Japan in the Victorian era. It grows rapidly and is notoriously painful to get rid of, specialist treatment is usually the most common way of getting rid of it, however it can be done yourself.

It is also problematic because it can knock value of your home (up to 10%) if you’re trying to sell, it can also affect your chances of getting a mortgage on a property… This is because it can cause damages to homes, it has been found to grow into properties, as well as damaging foundations and drainage systems. This is because the plant finds it incredibly easy to find it way through gaps and cracks. For example, it can find its way through the tiny gaps in tarmac and cracks in concrete and brickwork, meaning when it grows through these structures they become less stable.

The plant completely dies back in the winter months and lies ‘dormant’ until the spring. As mentioned before it grows very quickly up to 10cm per day, so the characteristics you need to keep your eye out for change often due to its aggressive growth.

A familiar site across the UK, a Japanese Knotweed Infestation.

Identifying Japanese Knotweed

If you’d like help identifying Japanese Knotweed, then check out our guide which can be found on our blog here.

Why You Should Try to Prevent the Spread of Japanese Knotweed?

It isn’t illegal to grow Japanese Knotweed on your own land, however it is required that you must prevent Japanese Knotweed on your land from spreading into the wild or onto a neighbour’s property. This is covered by legislation (Wildlife and Countryside Act 1981, Section 14) meaning you could face prosecution if it does spread from your land or given a community protection notice for causing a nuisance if you allow it to spread to anyone else’s property.

If you have Japanese Knotweed growing on your land and you want to simply remove it just by cutting it back and digging out the roots, you may want to think again. As a plan needs to be in place because soil or plant material that is contaminated with non-native plants can cause ecological damage and spread the plant further it is classified as a controlled waste.

Due to this composting the plant material and the surrounding soil is forbidden. Another problem is because the Rhizome (roots system) can lay dormant for many years and all it takes is a tiny fragment of this rhizome to be aggravated for it to trigger its re-growth again.

Injecting Japanese Knotweed with glyphosate based weed killer
Spraying Knotweed with Glyphosate based weed killer is a preferred method, however some evidence suggests that injection straight into the stems may work better.

1. Spraying with Chemicals

Using weed killer is probably the most preferred method of control as well as one of the cheaper options to go for. However, this method requires treatment over 3 or 4 years. If you do it yourself by using a glyphosate-based weed killer like Roundup Tree Stump Weedkiller. If using a professional to treat the infestation, they will probably be able to do it in half the time as they will have access to stronger and more powerful weed killers another bonus of this is that it will usually be covered by a guarantee which states if the plant grows back after treatment, they will treat it again free of charge.

Some professionals have now moved towards using weed killers of which they inject into the bamboo-like stems of the plant rather than spraying them. This is because the weed killer can kill any other plants nearby if it gets sprayed accidentally.

Glyphosate-treated Japanese Knotweed will produce a smaller-leaved, bushy regrowth the following spring and it is important to then treat this again or the infestation will just grow back the following year in the spring after it has died back to the rhizome crown in the winter.

Japanese Knotweed being sprayed with weed killer
Japanese Knotweed being sprayed with weed killer.

2. Burning It

Burning Japanese knotweed is an effective way to eradicate it from a site rather than burying it, it’s also a cheaper option. You can only burn the plant when it is absent of moisture, so the plant needs to be dug up and out the ground and then left to dry out first. You must ensure that all parts of the plant are fully dried out.

Once the parts of the plant are fully dried out it can be properly burnt. Once it has been burnt there is relatively no possibility of it re-growing. After it has been burnt it is critical to make sure the whole plant is burnt and disposed of properly. The Environment Agency and the Government have some guidelines on burning Knotweed.

If you are a business or a farmer and you wanting to dispose of Japanese Knotweed by burning it, you need to tell the Environment Agency one week before you burn it and also the environmental health officer at your local council. This is not required if you are a private individual burning the waste privately, however you still need to check with your local council that burning is allowed.

There is not enough evidence to support that burning kills the rhizome and crown of Japanese Knotweed, so it is advised that any remaining plant material is either buried… or disposed of off-site however there are rules and regulations around moving and transporting Japanese Knotweed. If you’re a business and you need to dispose of any left over plant material you need an environmental permit or registered waste exemption.

Japanese Knotweed being burnt
Burning Japanese Knotweed.

3. Burying It

This video shows the process of Japanese Knotweed Excavation and Burial on a commercial site.

If timescale is a problem for you and you don’t have the time to wait multiple seasons for a herbicide treatment plan, then excavation and burying is the alternative, however it is much more expensive. The guidelines for Japanese knotweed burial can be found in the Environment Agency document ‘Treatment and disposal of invasive non-native plants: RPS 178’. This can be viewed online here.

Once excavation of the Japanese Knotweed is complete, the knotweed and the surrounding soil must be:

Removed to an authorised landfill site, Relocated to a different part of the affected site or Buried in a hole on the affected site. You will not normally be allowed to bury waste on land unless it’s at a landfill site that has a suitable permit, so you need to check this with your Environment Agency or local council first.

If you want to bury Japanese knotweed on the site it came from you must:

  • Bury it at a depth of at least 5 metres.
  • Cover the plant remains with a material that does not allow the plant to grow through it (known as a root barrier membrane layer)
  • Do not bury any other types of waste with it.

Where it’s not possible to bury the plant 5 metres deep, you should wrap a root barrier membrane layer completely around the plant remains and bury them at a depth of at least 2 metres. It’s possible for even a small fragment of rhizome (root) to grow into a whole new plant if left in the soil, this is why the membrane is used to contain the left over roots, stopping its potential regrowth which is also helped by the depth it is buried at.

Root barrier membrane used to stop Japanese knotweed growing through on a development site
An example of a root barrier membrane on a large development site.

How can JKWClaims Help You

JKWClaims will organise for surveyors to assess your Japanese Knotweed infestation, they will also figure out the extent of the problem. We then work with solicitors to get you the maximum amount of compensation to help fund the removal of the plant.

If you think you may have an infestation please Get in touch today.

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