Japanese Knotweed in the UK

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Introduction

Japanese knotweed is the most invasive species of knotweed in the United Kingdom. The pernicious perennial continues to spread throughout the country via its rhizome fragments, causing costly and stressful situations for those liable for the land any infestation is found upon.

Knotweed grows in large patches that can quickly push out any other competing plant life, known to cause damage to property foundations, drainage pipes and even tarmac driveways and paths. Due to the devastating effects the plant carries with it, it now depreciates the value of a property by around 15%.

Japanese Knotweed Hotspots Across The UK

The north west of England, as well as Wales, the Midlands and London are among the worst affected locations. Knotweed Services has seen the following in the last 18 months; Bolton in Greater Manchester recorded 621 outbreaks of the weed over the last year, followed by Bristol, which had 465 infestations; St Helens, with 440; Cardiff, with 419; and Blackburn, with 406.

Llanelli and Swansea in South Wales, Rotherham, Shepherd’s Bush in West London and Nottingham rounded out the top ten.

How To Identify Japanese Knotweed

Japanese Knotweed is frequently misidentified across the UK. Often mistaken for other common weeds, infestations will spread rapidly from hidden underground rhizomes.

The best time to spot Japanese knotweed is in mid-summer or during early autumn. During spring, red tinted shoots appear from the ground and fat, asparagus-like spears rapidly lengthen from bright pink crown buds. Having the ability to grow several cm’s per day, these rapidly form dense stands of bamboo-like stems that further develop green heart or shield-shaped leaves. Click here for a more detailed article on how to identify Japanese Knotweed.

Here’s a detailed list of the tell-tale signs for UK Japanese Knotweed;

  • Red tinted shoots emerge around Spring.
  • In late spring, canes can reach up to 3 metres (10 feet) in height.
  • Shield/Heart shaped 20cm long leaves unravel early Summer.
  • Hollow bamboo-like canes begin to turn brown in late summer.
  • Flowers form in small white clusters from September.
  • Throughout the year, Rhizomes or root cluster can be identified by their dark brown exterior and yellow/orange interior.
  • Starting in late Spring, leaves grow in a zig-zag staggered pattern on the plants’ stem.
  • During Winter, it appears to die back as its leaves turn brown and drop off.
  • Throughout winter, stems turn completely brown while the plant’s rhizome network is still thriving below the surface.

Spring (March – April)
Shoots and stems are a purple/red colour with curled pinky reddish leaves. As the canes grow the leaves gradually unfurl and turn green.

Summer (May – August)
Shoots and stems are green with purple speckles. Leaves become heart shaped and turn green.

Autumn (September – October)
Stems are virulent, growing upwards of up to six feet, cream/white flowers appear late summer/autumn.

Winter (November – February)
Stems change to dark brown and are hollow, brittle and absent of leaves or flowers.

Japanese knotweed in the 4 seasons

If you think you have identified, or even suspect you may have a Japanese knotweed infestation, it’s always recommended to call an expert–someone who knows what they’re doing, like the experts at Knotweed Services.

Most Effective Japanese Knotweed Treatments

Although the plant may seem fiercely undefeatable, with professional help, it can be dealt with. To completely eradicate your Japanese knotweed infestation, there are several options such as herbicide treatment, electrical removal (this has zero negative effect on the environment), excavation, screening – you can find information on all above: click here for commercial removal and here for residential removal to find out more. 

For residential removal the plant is typically treated with chemical herbicides over the course of 3 years. This is done through professional-grade glyphosate herbicide application. As a PCA-accredited company that can offer a guarantee — our removal services are trusted by mortgage lenders and any potential buyers.

What is the Law on Japanese Knotweed?

Although it is not illegal for you to have Japanese knotweed on your property, it is against UK law to allow the plant to spread into the wild. The law states you can be prosecuted or given a community protection notice for allowing Japanese Knotweed to spread onto anyone else’s property from your own.

Due to the lack of support from insurance companies for Japanese knotweed eradication, any neighbouring properties that your infestation may spread to will now fall solely under your responsibility to correct. Japanese knotweed can be one of the most expensive headaches your property can throw at you. Stay vigilant and call us if you suspect the weed growing on your property.

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