Japanese knotweed is a fast-growing, invasive weed that can damage buildings, roads, and pipelines. 

Japanese knotweed grows quickly and can easily overtake an area. It’s also incredibly tough to get rid of, as it spreads rapidly and regenerates from just a small piece of the plant.

So, in this blog, we answer the question “What is Japanese Knotweed?” with a concise guide to teach you everything you need to know about this troublesome weed, including how to identify it, control it, and get rid of it for good.

Japanese knotweed is a highly invasive, fast-growing weed that can grow up to ten centimetres per day. Its proclivity for rapid growth has the potential to cause significant harm to property and infrastructure.

How was Japanese Knotweed introduced to the UK?

Japanese Knotweed (Fallopia japonica) is a native of Japan that was introduced as an ornamental garden plant during the Victorian era. It quickly suffocates other plants and aggressively colonises any area where it is allowed to thrive, growing up to a metre every month.

The non-native plant spreads quickly, with bamboo-like branches and big brilliant green leaves growing up to 2 metres long and a complex subterranean rhizome network, making it difficult to eradicate. Pulling the plant up will not stop it from spreading; in fact, it may make it grow even quicker.

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Flowers of Japanese knotweed, Fallopia japonica beginning to grow at the start of summer

Japanese Knotweed characteristics

At first glance, Japanese Knotweed is often confused with other plants that look similar. Knotweed has specific characteristics at each step of its life cycle.

Early in the spring, crimson or purple shoots emerge, growing into canes with leaves that unroll and turn green.

As summer approaches, Japanese Knotweed is completely matured with its hollow, and speckled stems. They can reach a height of three to four metres. The Japanese Knotweed blooms in late summer, producing clusters of little creamy-white flowers that blanket the area surrounding it.

Japanese knotweed roots, also known as rhizomes, are the plant’s large underground component. The rhizome is orange or yellow in colour. The nodes are normally one or two centimetres apart.

How does Japanese Knotweed spread?

Because Japanese Knotweed may grow from as little as 2mm of rhizome, it is classified as “controlled waste” under the Environmental Protection Act of 1990 and must be disposed of only in licenced landfill sites to prevent further spread.

Attempts to eradicate Knotweed should only be undertaken by licenced specialists. If even a small bit of the plant is left in the soil, even a few inches, it will swiftly sprout again. Only by destroying the plant’s entire underground root structure can it be eradicated.

Damage caused by Japanese Knotweed

Japanese Knotweed can do a lot of damage. Knotweed can flourish in a wide range of growth situations because of its sturdy, robust plant structure. The plant’s growth rate is unaffected by soil pH or salinity, and it can withstand temperatures as low as -35°C.

This is how it gets into cracks in concrete and masonry, where it can take hold and cause structural damage to driveways, roadways, and property foundations.

Damage from Japanese knotweed can expand to pipes and sewers. Not only blocking them but also cracking them. - what is japanese knotweed
Damage from Japanese knotweed can expand to pipes and sewers. Not only blocking them but also cracking them.

This can have a significant impact on the value of your house as well as your ability to obtain a mortgage.

Its propensity to grow up to 10cm per day during the summer means it can easily outgrow competitors and pose a hazard to the property by taking root within foundations.

The root systems of Japanese Knotweed can grow up to three metres deep and seven metres in all directions. As a result, removing the roots is a difficult and time-consuming task.

Japanese knotweed and the law

The disposal and control of Japanese Knotweed are governed by severe legislation because it is an invasive species capable of causing enormous harm.

It is not a legal obligation to report Japanese Knotweed, however, it is a legal necessity to declare Japanese Knotweed on the TA6 form if you are selling your house, and if it is, you must also give a Japanese Knotweed management plan to fulfil mortgage lender requirements.

Is it illegal to have Japanese Knotweed on my land?

It is not unlawful to have Japanese Knotweed on your property, but it is forbidden to enable it to spread to a neighbouring property or adjacent land.

Individuals who have Japanese Knotweed on their property have a legal obligation to prevent the weed from spreading to nearby areas. Failure to prevent Japanese Knotweed from spreading to neighbouring houses is a crime punishable by an Antisocial Behaviour Order (ASBO) and a fine of up to £2,500.

If you notice Japanese Knotweed in your neighbour’s garden or on neighbouring land, you should communicate with your neighbours or the landowners immediately, since they may already be taking action to prevent the spread of Japanese Knotweed.

You can contact your local council if the homeowner or landowner does not take action. They may then decide to take legal action. With the number of legal cases rising it is becoming easier to enforce property owners with Japanese knotweed on their property to take action before it costs them dearly.

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Area cleared of Japanese knotweed on a property with a treatment plan

How to get rid of Japanese Knotweed?

If you suspect your property contains Japanese Knotweed, you should have a Japanese Knotweed survey done to determine the extent of the problem and the best course of action for your property’s future usage.

Herbicides ranging from foliar sprays to stem injections, as well as physically excavating the Japanese Knotweed and dumping it off-site, are all options for treatment and eradication. These can range wildly in price depending on the coverage of the infestation.

You can of course take a DIY approach, but professional intervention is best as this is not a quick process and take many years to resolve with a well-planned treatment program.

In conclusion

What is Japanese Knotweed?

Whether you call in professional help or try to undertake it yourself, this will all depend on what you want from your property.

For example, if you sell then it is normally a requirement in order to meet the mortgage requirements, mortgage lenders frequently want a detailed Japanese Knotweed management plan and an Insurance Backed Guarantee from a professional contractor.

However, if you intend to live at the property for a number of years and have both the time and energy, then a DIY approach can be undertaken first.

Bear in mind that you will not be covered in the event of future regrowth if you do not have an Insurance Backed Guarantee, which may be a condition for buyers to secure a mortgage for your property.

Carefully think about the time and investment required to protect your precious assets.

Want to know more about selling or buying a property affected by Japanese knotweed

Knotweed Removal aims to provide the most up-to-date information, help, and advice for YOU to make informed decisions. If you are unsure or uncertain about how to proceed, please reach out to us and we will gladly come back and advise you as best we can.

Governmental advice can be found here and the UK law covering the removal of Japanese Knotweed as stated under the Wildlife and Countryside Act 1981 can be found here.

The best means to contact us is via our email – hello@knotweedremoval.tips

Do not forget we have a library of blogs covering many areas relevant to Japanese Knotweed, our free downloadable How-to Guides, and Product Reviews on the latest methods being employed to eradicate or remove Japanese Knotweed.

Knotweed Removal, UK

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