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If you are a homeowner, landlord or developer in the UK, you might have heard about Japanese Knotweed. This invasive plant species has become a significant problem, causing substantial damage to properties nationwide. If left unchecked, Japanese Knotweed can grow rapidly, cause damage to structures, roads, and other infrastructure, and even decrease the value of your property. This blog will explore what it is, how to identify it, and the various methods available to control and eradicate it.

Japanese Knotweed

What is Japanese Knotweed?

Japanese Knotweed (Fallopia japonica) is a non-native invasive plant species that has caused problems in the UK since its introduction in the 19th century. It is a perennial plant that can grow up to 3-4 meters tall, with hollow stems covered in purple speckles. The leaves are heart-shaped and grow in an alternating pattern along the stem, while the flowers are small, cream-coloured and grow in clusters.

It spreads rapidly, with a single stem growing up to 10cm per day, and it can quickly colonize large areas. The plant is hard to control because it spreads via underground rhizomes, which can grow up to 7 meters away from the parent plant and through tarmac, concrete, and other hard surfaces.

Identifying Japanese Knotweed

Identifying the plant is not difficult if you know what to look for. The plant’s physical features are unique and distinguish it from other plants. The plant starts to grow in the spring, and red or purple asparagus-like shoots emerge from the ground. As the plant grows, the stem becomes hollow, and the leaves grow. The leaves are large and shield-shaped, with a flat base and pointed tip. In the autumn, the leaves turn yellow before falling off, leaving the woody stem behind.

The Risks Associated with Japanese Knotweed

Japanese Knotweed poses several risks to properties and the environment. Its roots can damage buildings, roads, and other infrastructure, and the plant’s rapid growth can choke out native plants, leading to a decline in biodiversity. The presence of the plant can also make it harder to obtain a mortgage or sell a property. The plant is classified as ‘controlled waste’ under the Environmental Protection Act 1990, meaning it has to be disposed of at a licensed landfill site.

It is classified as an invasive species under the Wildlife and Countryside Act of 1981 and the Anti-Social Behaviour, Crime and Policing Act of 2014. Property owners have a legal obligation to manage the plant on their properties, and they can face fines and legal action if they fail to do so. The law also requires property owners to prevent it from spreading to neighbouring properties and the wider environment.

Controlling Japanese Knotweed

Several methods are available for controlling Japanese Knotweed, but it is not easy to eradicate it completely. The most effective way to control the plant is through chemical treatment, using herbicides that target the plant’s root system. Physical control methods, such as digging up the plant and removing it, can also be effective, but they can be time-consuming and expensive. Biological control methods, such as introducing the plant’s natural enemies, are still being researched and are not yet widely available.

Eradicating Japanese Knotweed

Eradicating the troublesome plant is challenging and can take several years to achieve. The most effective way to eliminate the plant is through chemical treatment, but it requires several rounds of treatment to kill the plant’s root system. Once the plant has been eradicated, ongoing monitoring and management are necessary to prevent the plant from re-growing. Ongoing maintenance can also be expensive, and it is essential to hire a professional to ensure the eradication is successful.

Preventing the Spread of Japanese Knotweed

Preventing the spread of Japanese Knotweed is crucial in controlling its growth and spread. Homeowners and developers should be careful when carrying out activities that could spread the plant, such as landscaping, gardening, and excavation work. It is also essential to dispose of Japanese Knotweed safely and legally. The plant is classified as ‘controlled waste,’ It should be disposed of at a licensed landfill site. Failure to dispose of Japanese Knotweed correctly can result in legal action and fines.


Japanese Knotweed is a significant problem in the UK, and it can cause substantial damage to properties and infrastructure. Property owners, developers, and homeowners need to understand the risks associated with the plant and take appropriate action to manage and control it. The best way to control Japanese Knotweed is through chemical treatment, physical control, or biological control, but it requires ongoing management and monitoring to ensure success. It is essential to hire a professional to carry out the eradication process to ensure it is successful.

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