December 11, 2023

All You Need To Know About Japanese Knotweed

Japanese Knotweed, scientifically known as Fallopia Japonica, is an uninvited guest in Britain that has become a source of worry for property owners across the country. This invasive plant species, despite its ornamental appeal, is a relentless intruder causing significant trouble in various regions across the UK. This article aims to reveal the key facts and figures about Japanese Knotweed in the UK, its origin, identification, potential hazards, and the most effective methods of control.

1. Understanding Japanese Knotweed

1.1 What is Japanese Knotweed?

Japanese Knotweed is a highly invasive perennial weed that originates from East Asia, specifically Japan, China, and Korea. It’s known for its swift growth that leads to the formation of dense clumps, and its capability to cause serious damage to buildings and infrastructure due to its robust root system, known as rhizomes. This plant can grow up to 7 feet tall, with distinctive shovel-shaped leaves and a zig-zag pattern along its stems1.

1.2 How did it Arrive in the UK?

Japanese Knotweed was introduced to the UK in the early 19th century by a German physician named Philipp Franz von Siebold. Originally admired by botanists for its ornamental value, it eventually spread into the wild and became a persistent nuisance within the British ecosystem1.

1.3 Spread Across the UK

Since its introduction, Japanese Knotweed has spread across the entire UK. In fact, it is estimated that at least one infestation exists in every ten square kilometres of Britain2. The plant has managed to infiltrate even the most high-profile sites, such as the 2012 Olympics site in London, which required a four-year effort to control the infestation2.

2. Identifying Japanese Knotweed

One of the first steps in combating the spread of this invasive species is knowing how to identify it. During the spring, the plant produces reddish-purple shoots from crimson-pink buds at ground level, eventually forming tall bamboo-like canes1. As the plant matures, the leaves become shovel-shaped and can grow up to 5 and a half inches long1. In winter, the plant appears dead, with only dark brownish-red stems visible above the ground3.

3. The Ecological Impact of Japanese Knotweed

Japanese Knotweed is known for its capacity to outgrow and suppress native vegetation, creating a hostile environment for local wildlife, plants, and insects2. It also releases chemicals into the soil that can inhibit the growth of other plants3. The plant’s large overwintering canes can block water channels, increasing the likelihood of flooding3.

4. Health Implications and Uses

Despite being a nuisance for property owners, Japanese Knotweed isn’t poisonous and is safe to touch1. Interestingly, it has been used in traditional Japanese medicine as a painkiller23. The plant’s young shoots are also edible, often compared to rhubarb in taste, and can be used in a variety of dishes14.

5. The Impact on Property Prices

Japanese Knotweed can significantly affect property prices. Its rampant growth and potential to cause damage to foundations, walls, and paths can impact the value of affected properties1. Mortgage companies have also been known to refuse lending on properties infested with the plant2.

6. Preventing the Spread of Japanese Knotweed

Preventing the spread of Japanese Knotweed involves careful handling to avoid breaking or moving the stems or uprooting the plant1. The plant spreads through fragments of cut stems and rhizomes, which can create new shoots and roots when buried in soil1. Therefore, it’s critical to exercise caution when dealing with this invasive species.

7. Removing Japanese Knotweed

The removal of Japanese Knotweed is a complex process and should be handled by trained and qualified specialists1. This is because the risk of the weed spreading is very high when not dealt with correctly1. Various herbicides, when applied correctly, can effectively kill Japanese Knotweed1.

8. Legal Implications

The presence of Japanese Knotweed and the failure to control it may have legal implications. If the plant spreads beyond your property and causes a nuisance, you may be liable for any damages5. Also, when selling a property, you are legally required to disclose the presence of the plant3.

9. Treatment and Control Methods

There are two main methods for controlling Japanese Knotweed, namely herbicide treatments and excavation3. Glyphosate-based herbicides are commonly used, and if applied correctly, they can eradicate the plant, although it can take two to three years of repeated treatment5.

10. Impact on the Built Environment

Japanese Knotweed is known to cause substantial damage to the built environment. It has been estimated that over 2% of development sites and 1.25% of residential properties in Great Britain are affected by the plant3. This invasive species can significantly reduce the value of land and property2.

11. Reporting Sightings of Japanese Knotweed

If you spot Japanese Knotweed, it’s important to report it. Sightings can be recorded using the iRecord App or the LERC Wales App5. These records contribute to a better understanding of where invasive species are located in the UK, how they spread, and their impact5.

12. The Future of Japanese Knotweed Control

The control of Japanese Knotweed is an ongoing issue in the UK. While there are effective methods for managing the plant, it is a persistent pest that requires constant vigilance. Future measures may involve biological control methods and further legislative action to mitigate its spread2.

In conclusion, Japanese Knotweed is an unwelcome guest in the UK, causing significant problems for homeowners, businesses, and the environment. However, with the right knowledge, caution, and professional assistance, its spread can be controlled, and its impact minimized.

Note: This is a fictional article and is meant only to provide an example of how to write an SEO-friendly, unique blog post using multiple sources and markdown formatting. The information in the article may not be accurate or up-to-date.


  1. Taylor Total Weed Control 2 3 4 5 6 7 8 9 10 11 12
  2. Dr Paul Beckett 2 3 4 5 6 7
  3. Species Information 2 3 4 5 6 7
  4. FLPA/Paul Miguel/REX/Shutterstock
  5. Natural Resources Wales 2 3 4