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Japanese Knotweed

Blackdown

Japanese knotweed is classed as an invasive species due to it’s strong characteristics of rapid growth. Surveys suggest that there’s at least one infestation for every ten square kilometres in Britain.

 

What is Japanese Knotweed?

Japanese Knotweed Stalks

Japanese Knotweed (Fallopia japonica) is a fast-growing, rapidly spreading perennial weed. It is officially one of the UK’s most hated, feared and potent invasive species. Originally introduced to the UK in the 1800s by the Victorians as an ornamental garden plant. As a weed it isn’t toxic, although it’s all-consuming and covers the ground so comprehensively that where dense stands form, it shades the ground, excluding native ground flora.

 

How can I identify Japanese Knotweed?

The identification of Japanese Knotweed is not always easy, but to ignore an infestation could potentially be very destructive and have costly consequences.

During mid-summer and early autumn, Japanese knotweed is easier to spot and identify. During spring, reddish/purple shoots begin to appear from the ground and thick ‘spears’ rapidly begin to lengthen from the crimson-pink buds. During the summer, these shoots grow rapidly into dense large strands of bamboo-like ‘canes’ which can grow up to 2.2m tall. The canes are identifiable by their purple flecks and produce branches along its length. The leaves of Japanese knotweed are shovel/heart-shaped and can be up to 14cm in length.

During the winter, the stems of the plant die back to ground level, but the canes remain for several months longer. Each year, stem growth is renewed from the stout of the plant, deeply-penetrating rhizomes.

Japanese knotweed can often be confused with similar looking plants such as; Fallopia baldschuanica (Russian vine), Leycesteria formosa (Himalayan honeysuckle) or Houttuynia cordata.

Himalayan honeysuckle - Leycesteria Formosa    Russian Vine Fallopia Baldschuanica    Houttuynia Cordata

 

Japanese Knotweed

Characteristics of Japanese knotweed:

  • Fleshy, reddish/purple-tinged shoots
  • A stem that resembles bamboo
  • In spring, look out for fast growing, tall stems with lots of green leaves
  • In late summer (August – September), you’ll be able to see clusters of cream flowers.
  • In winter, the plants leaves die off
  • Large heart or spade-shaped leaves

 

How can Knotweed effect your business?

Japanese knotweed can be a huge problem to property, as the plant grows rapidly, sometimes up to 10cm per day. It has been known to cause structural damage to buildings, so it is important to call an expert immediately for advice.

This invasive weed can typically damage the following;

  • Building foundations
  • Tarmac, paving and general road surface
  • Retaining wall structures
  • Potential reduction in property value

 

How to deal with Japanese knotweed

DO

  • Treat Japanese knotweed as soon as you are aware of it, the quicker you identify and manage knotweed the less damage it can cause.
  • Ensure that all clothing items that have come into contact with knotweed are washed thoroughly to ensure that the weed doesn’t spread further.
  • Remember to check any previously contaminated areas for up to 2-3 years after removal, to ensure there is no regrowth.
  • Contact us at NBC Environment to speak with an expert today.

 

DON’T

  • Do not attempt to cut or dig up the plant yourself, this could potentially stimulate growth.
  • Do not use a lawnmower, strimmer or hedge cutter to remove knotweed, this can infect surrounding areas and encourage further growth.
  • Do not dispose of any cuttings in general garden waste or compost, this could ignite another outbreak.
  • Do not spread any soil that has come into contact with Japanese knotweed.
  • Do not try to burn knotweed it is immune to burning.

 

If you leave just one small piece of rhizome (root like structure that joins the individual stems together below ground) behind it may grow into a new plant, which will begin to spread.

 

If you feel you have identified a plant to be Japanese Knotweed and would like advice on how to manage it,
contact us and speak with our experts to see how we can help you.

 

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