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Understanding Japanese Knotweed :

The Plant that Took Over the World

A Brief History of Japanese Knotweed 

Japanese Knotweed, or Fallopia japonica, originally hails from Eastern Asia, specifically Japan, China, and Korea. Its ornamental characteristics and rapid growth made it an attractive choice for Western horticulturists during the 19th century. But little did they realize that this seemingly harmless plant would turn into one of the most invasive species in Europe and North America.

Why is Japanese Knotweed a Concern?

We must understand that while Japanese Knotweed’s rapid growth can be seen as an advantage,

Japanese knotweed taking over a path

Japanese knotweed taking over a path

this quality is precisely what makes it so invasive. The plant’s aggressive spread means it can quickly overtake native species, reducing biodiversity. This isn’t just an environmental issue.

Its strong rhizomes and roots can penetrate through cracks in concrete, causing structural damage to buildings, roads, and bridges. For property owners, the presence of Japanese Knotweed can lead to decreased property values and potential legal issues.

Identifying Japanese Knotweed

It’s crucial for us to be able to identify Japanese Knotweed, especially if we own land or are in the property business. This plant can grow up to 3-4 meters in height during its peak season. It has:

  • Bamboo-like stems: Hollow and reddish-brown, becoming brittle in winter.
Japanese knotweed canes

Japanese knotweed canes

  • Heart-shaped leaves: Bright green and up to 14cm long.
Hart shaped leaves

Heart shaped leaves

 

 

 

 

 

 

 

 

 

 

Clusters of cream flowers: Small and appear between late summer and early autumn.

  • Japanese Knotweed in full flower

    Japanese Knotweed in full flower

The Lifecycle of Japanese Knotweed 

Understanding the lifecycle of Japanese Knotweed allows us to take timely measures in its management. The plant emerges in early spring, growing rapidly throughout the summer. By late summer to early autumn, the plant flowers,

Japanese Knotweed in full flower

Japanese Knotweed in full flower

providing an easy identification window. Come winter, the plant dies back to ground level, but its underground rhizomes remain active, storing energy for the next growth cycle.

crown

crown

Managing and Controlling Japanese Knotweed

We’ve established that Japanese Knotweed is invasive and potentially damaging. However, all is not lost. There are several ways we can manage and control its spread:

  1. Physical removal: This involves excavating the plant along with its extensive root system. It’s labor-intensive and needs to be done meticulously to ensure no remnants are left behind.
  2. Chemical treatment: Using herbicides like glyphosate can be effective. However, multiple treatments are often required over several years. It’s crucial to follow the guidelines to avoid harming native plants or water sources.
  3. Biological control: Certain insects, like the Japanese Knotweed psyllid, feed on the plant and can act as a control method. However, introducing a new species can have other ecological impacts, so this method is still under research and not widely adopted.

Legislation and Japanese Knotweed

Many countries have recognized the threat of Japanese Knotweed and have enacted laws and regulations to control its spread. We need to be aware of these regulations, especially if we’re in the property or construction sectors. In the UK, for instance, it’s illegal to plant or cause Japanese Knotweed to grow in the wild.

The Economic Impact of Japanese Knotweed

We cannot ignore the economic repercussions of Japanese Knotweed. The cost of managing and eradicating Japanese Knotweed runs into millions each year for many countries. For property developers and homeowners, the presence of the plant can result in legal battles, repair costs, and decreased property values.

The Lifecycle of Japanese Knotweed

Understanding the lifecycle of Japanese Knotweed allows us to take timely measures in its management. The plant emerges in early spring, growing rapidly throughout the summer. By late summer to early autumn, the plant flowers, providing an easy identification window. Come winter, the plant dies back to ground level, but its underground rhizomes remain active, storing energy for the next growth cycle.

Managing and Controlling Japanese Knotweed

We’ve established that Japanese Knotweed is invasive and potentially damaging. However, all is not lost. There are several ways we can manage and control its spread:

Physical removal:

This involves excavating the plant along with its extensive root system. It’s labour-intensive and needs to be done meticulously to ensure no remnants are left behind.

Chemical treatment:

Using herbicides like glyphosate can be effective. However, multiple treatments are often required over several years. It’s crucial to follow the guidelines to avoid harming native plants or water sources.

Biological control:

Certain insects, like the Knotweed psyllid, feed on the plant and can act as a control method. However, introducing a new species can have other ecological impacts, so this method is still under research and not widely adopted.

Legislation and Japanese Knotweed

Many countries have recognized the threat of Knotweed and have enacted laws and regulations to control its spread. We need to be aware of these regulations, especially if we’re in the property or construction sectors. In the UK, for instance, it’s illegal to plant or cause Japanese Knotweed to grow in the wild.

The Economic Impact of Japanese Knotweed

We cannot ignore the economic repercussions of Knotweed. The cost of managing and eradicating Knotweed runs into millions each year for many countries. For property developers and homeowners, the presence of the plant can result in legal battles, repair costs, and decreased property values.

Knotweed is more than just a plant. It’s a symbol of the unintended consequences that can arise from moving species across continents. While its ornamental appeal is undeniable, the challenges it presents are significant. Through understanding, early detection, and rigorous management techniques, we can control its spread and mitigate its impacts.

Inform your mortgage lender about the presence of the plants

as it can impact the value of your property and make it difficult to secure a mortgage. Some mortgage lenders may require a specialist survey to be carried out and a management plan to be in place before they will lend on a property affected by  knotweed.

The cost of managing knotweed can vary, depending on the extent of the infestation and the location of the property. However, it is important to engage a professional specialist company to carry out the treatment program, as DIY methods are unlikely to be effective and may even spread the plant further.

In many cases, it may be possible to sell a property with this invasive weed.

the plant must be managed effectively and the buyer must be informed about its presence. The sale of a property with Japanese knotweed is subject to specific legislation, including the Environmental Protection Act 1990, which requires the seller to disclose the presence of the plant.

To summarize, Japanese knotweed is a highly invasive plant species that may cause significant damage to buildings and structures. It can impact the value of a property. It is important to identify the plant and seek professional advice from a specialist company to manage the infestation effectively. The cost of managing knotweed can vary. You should engage a professional specialist to carry out the treatment program. Informing your mortgage lender and potential buyers about the presence of the plant is also crucial. It could reduce the value of your property and make it difficult to secure a mortgage. so it is possible to manage Japanese knotweed and protect your property from the damaging effects of this invasive plant.

 

If you would like any information regarding Japanese knotweed Call Stephen on:07753682333