December 4, 2023

12 Facts About Japanese Knotweed

Japanese Knotweed, scientifically known as Fallopia japonica, is a highly invasive plant species that has been causing significant disturbances in the United Kingdom and other parts of the world. In this comprehensive article, we delve into the depths of this troublesome plant, exploring its origin, characteristics, effects, and the essential facts that everyone should know.

1. Origin of the Japanese Knotweed

Japanese Knotweed, as the name suggests, originated from East Asia, thriving in countries like Japan, China, and Korea¹. The plant was brought to Britain in the early 19th century by a German physician named Philipp Franz von Siebold². Initially, it was valued for its ornamental qualities but soon began to spread uncontrollably, turning into a persistent problem².

2. Identification and Characteristics of Japanese Knotweed

To tackle Japanese Knotweed effectively, it’s essential to know what it looks like. The plant can be identified by its unique features. During spring, reddish-purple shoots emerge from crimson-pink buds at ground level. These shoots grow swiftly, forming dense stands of tall, bamboo-like canes that can reach up to seven feet².

The leaves of the Japanese Knotweed are shovel-shaped and can grow up to 5.5 inches long. They have a zig-zag pattern along the stems². Although it may seem lifeless in winter, shedding its leaves and appearing dead, it is merely dormant and will resurrect in spring³.

3. Growth Rate and Proliferation

Japanese Knotweed’s growth rate is alarmingly fast. In its prime growing season, the plant can grow by up to 10cm a day¹. It displays a remarkable ability to exploit weaknesses in structures, growing through walls, tarmac, and even concrete¹⁴. This rapid and aggressive growth is a significant factor contributing to its invasive nature.

4. Impact on Property Value

The presence of Japanese Knotweed can significantly reduce the value of properties. Mortgage lenders have been known to refuse mortgages on properties affected by this invasive species¹. The plant can cause severe damage to building foundations, flood defences, driveways, and more⁴. This damage, combined with the cost of eradication, can be a significant financial burden.

5. Control and Eradication

Eradicating Japanese Knotweed is a challenging task that can often take several years due to the plant’s rapid growth and resilience¹. It is crucial to get the issue resolved and treated before it can spread to neighbouring properties⁴.

The law prohibits allowing the spread of Japanese Knotweed, and individuals can be prosecuted if it encroaches on neighbouring land¹. All parts of the plant are classified as controlled waste and must be disposed of carefully to prevent further spread¹.

6. Ecological Impact

Japanese Knotweed is one of the world’s 100 worst invasive species¹. Its rapid growth and ability to smother other species make it a significant threat to biodiversity[^5^]. It can create a hostile environment for local wildlife, birds, plants, and insects³.

7. Edibility and Use in Traditional Medicine

Despite its notorious reputation, Japanese Knotweed has some beneficial uses. The young shoots of the plant are edible and can be used in sauces, soups, and desserts². They provide a good source of vitamin A². Additionally, the Japanese use the plant in traditional medicine as a popular painkiller³.

8. Cost to the Economy

The control and management of Japanese Knotweed cost the British economy an estimated £166 million⁴. The cost of keeping it under control could add 10% or more to the budget of development and construction projects⁴.

9. Prevalence in the UK

It is estimated that there could be one infestation every 10 square metres in the UK⁴. This rapid spread and proliferation make Japanese Knotweed a significant concern for property managers, surveyors, and planners⁴.

10. Legislation Surrounding Japanese Knotweed

Understanding the legislation around Japanese Knotweed is crucial for property owners and managers. Individuals are held liable if the knotweed spreads onto neighbouring land⁴.

11. The Impact on House Prices

As a result of its ability to cause damage to property foundations, walls, and paths, properties affected by Japanese Knotweed risk having their value reduced².

12. Preventing the Spread of Japanese Knotweed

The prevention of Japanese Knotweed spread is crucial. If discovered, it is advised not to attempt to break or move stems or uproot the plant². Instead, trained and qualified specialists should be called in to deal with any recognised infestation².

Conclusion

Understanding the characteristics, impact, and control methods of Japanese Knotweed is essential in tackling this invasive species effectively. While it may seem like a daunting task, with the right information and strategies, it is possible to manage and control this plant effectively.

Wise Property Care, Japanese Knotweed Facts ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸
Taylor Total Weed Control, Japanese Knotweed Facts ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹
Phlorum, [21 Fascinating Facts About Japanese Knotweed](https://www.phlorum.com/blog/2014/03/17/21-fascinating-facts-japanese-knot ↩ ↩² ↩³
Invasives, Japanese Knotweed ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸