Japanese knotweed identification to be better informed in deciding what course of action to take

There is no single doubt that so many beautiful things come from Japan. However, one of the things that the UK might not be grateful for is the Japanese knotweed. What exactly is Japanese knotweed, and why is it a big problem?

Japanese knotweed infestation on a neighbour’s property

The plant’s ability to flourish in any part of the country enhanced its popularity in the 19th century upon its arrival.  However, it did not take long before the plant started causing havoc across the UK.

Over the years, the plant has spread to unwanted areas like river streams, railway lines, and office areas, thus damaging properties and other resources.

What is Japanese knotweed?

Japanese knotweed is extremely invasive thus causing damage to properties. It has a bamboo-like stem and white flowers. It grows up to 12 cm a day! It can grow anywhere and spread within a short period.

The size of the Japanese knotweed leaves soak up all the nutrients, sun and water and starve other plants
The size of the Japanese knotweed leaves soak up all the nutrients, sun and water and starve other plants

How does it look like?

Several plants look similar to Japanese weeds, so being familiar with their identity is essential.  It is essential to know what it looks like to take quick measures when you notice it around your property. Here are the characteristics of the plant at different times of the year:

 How it looks in spring

  • During spring, you will see the first signs of Japanese knotweed growth (Around mid-march)
  • The plant showcases red-purple shoots that come with rolled back leaves that reproduce due to the stored nutrients in the rhizomes.

  How it looks in summer

  • During summer, the plant stem is similar to bamboo. However, it is greener and has purple speckles.
  • The canes store water and nutrients to help in plant growth.
  • The weed’s leaves are large with pointed tips and are an extension from the stem.
  • During the last few weeks of summer, the flowers that are creamy white start to hang in clusters.

 How it looks like in autumn

  • The bamboo stems begin to darken
  • The leaves become enormous and extremely pointed.
  • The leaves begin to turn yellow and wilt towards the end of the season.

 How it looks in winter

  • The plant’s leaves turn brown, and  it withdraws back to the rhizomes
  • The canes become darker and become wooden stalks that do not compose easily.
  • You will notice some shoots growing through the canes during the first few weeks of spring.
The pink stems of Japanese knotweed grow up to 10cm in spring
The pink stems of Japanese knotweed grow up to 10cm in spring

Where does it come from?

The Japanese knotweed was first transported to Britain by adventurer and Botanist Phillip Von Siebold. The botanist discovered the plant growing at the sides of the volcano in the East in the 19th century. The plant gained popularity over the years as it was sold in nurseries across the European continent.

The plant grew profoundly and rapidly, and most people planted it along the pathways to protect them against mudslides.  Those who lived in the cities used the Japanese knotweed to beautify their houses and paths. It will be correct to say that within two decades, the plant was found everywhere.

The knotweed grew so fast, and sooner than later, it became an issue along the railway lines, drainage system, basements, and rivers. This is the situation in most parts of the UK today!

How does Japanese knotweed spread?

The weed produces rhizomes instead of seeds like many other wild plants. Rhizomes are underground stems that send out the root system. This makes it easier for the plant to spread to other areas through the transportation of the top layer of soil.

The root system is widespread, making it harder to know the ground is not affected.

The shovel-shaped leaves soak up much sun for their exponential growth
The shovel-shaped leaves soak up much sun for their exponential growth

What does the Japanese knotweed do?

The weed has caused a lot of damage widely in the UK since the 19th century. Will the weed affect your property? The weed proliferates, thus leading to extensive damage to your home. It can clog your drainage systems and discolour walls.

The plant can grow up to 3 cm deep, which makes it even harder to eliminate.

This weed can devalue your property in the long run. Additionally, it will eventually spread to your neighbours, who might take you to court for damage. You may spend a lot in the process if they prove that the weed came from your property.

The presence of this weed will make it harder for you to get a buyer for your property if you so wish to sell. Most buyers will decline the offer until you have a long term solution in place.

The good news is that most UK property agents involve homeowners and local government in coming up with proper treatment solutions to ensure that homeowners can sell their property at a deserving value.

What can you do about it?

It can be very challenging to get rid of the Japanese knotweed. You will need the help of an expert to get the job correctly done. Cutting or digging is not a fruitful method of controlling this plant.

The plant has a comprehensive and established rhizome system that can be buried up to 5 meters underground, making its removal by digging ineffective. The rhizomes always remain in the ground and grow back so fast.

Here are some practical ways to eliminate this knotweed:

1.   Use herbicides

Using recommended herbicides can eventually get rid of this plant for good. Glyphosate–containing products are the most suitable herbicides.

However, these products should be handled by professionals. Ensure that the experts have proper certifications for the job. When appropriately applied at the right time of the year, glyphosate chemicals will eradicate the plant.

It is crucial to remember that for the chemicals to work; they must be applied during the last months of summer or the autumn after the flowering of the weed. It will take at least two years to get rid of the large stands of the plant.

Treatment should be done once a year during the recommended time.

2.   Excavation

Most of the home remedies to eliminate this weed end up ineffective. To entirely remove the plant and its roots, you will have to excavate to about 4 meters, followed by laying a weed–proof membrane with new clean soil placed on it.

The excavation method is not suitable in areas with structures or drainage systems. The excavation process is quite disruptive; it is also costly to dispose of contaminated soil.  It may not be an effective method if the neighbouring properties are not excavated as well.

3.    Mesh Treatment

Mesh treatment is a new weed treatment technique that uses an aggressive mechanism that forces the plant to be confined in a mesh that is placed where it grows. It is ideal for use on highways, riversides, and railway lines because it has no negative impact on the environment.


The Japanese weed can be challenging to control. However, timely and constant treatments can lower their impact. Different therapies are being developed each day, and we can only remain positive that more effective treatments will be available to homeowners soon.

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Want to know more?

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 on 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 – knotweedremovaltips@gmail.com

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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