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Japanese Knotweed

Japanese knotweed is an invasive perennial plant that spreads by rhizomes, which can extend up to 3 metres deep and 20 metres wide. It’s a large clump-forming plant, which grows up to 3 metres tall, with light green shield-shaped leaves.

Four species of invasive knotweeds are found in the Metro Vancouver region: Japanese knotweed, Bohemian knotweed, Giant knotweed, and Himalayan knotweed.

Japanese, Bohemian, Giant, and Himalayan knotweeds are classed as noxious weeds within all regions of the province under the BC Weed Control Act.

Why is it a problem?

Japanese knotweed grows rapidly and can quickly overtake native plant species. Its extensive root systems can cause damage to buildings, roads, and other infrastructure.

Furthermore, Japanese knotweed is difficult to eradicate once it has become established, as it can regenerate from small fragments of its root system. Improper handling can unintentionally spread the plant, worsening the problem.

Japanese knotweed is a major concern for property owners, as its presence can reduce the value of land. It is also a concern for local authorities, who have to manage the costs of controlling its spread and preventing its impact on the environment.

How do you Identify Japanese Knotweed?

The appearance of Japanese knotweed changes with the seasons, so it is important to consider the time of year when identifying the plant. Japanese knotweed is most easily identified during the spring and summer months. Key traits of Japanese knotweed are;

  • Red shoots emerge in spring that look like asparagus.
  • Leaves which are shield or shovel-shaped.
  • Stems that resemble bamboo canes with purple speckles.
  • Small, cream-coloured flowers developing towards the end of summer.

During autumn, the leaves will start to go yellow and wilt as winter approaches. The stems will change to a darker brown before the plant becomes dormant in winter.

Knotweed Images

The images below are a selection of knotweed plants at different stages and in different environments. However, knotweed can lie dormant in winter and the plant lifecycle can be difficult to identify. Contact us for more information!

Ready for Help?

Learn more about how we can help to remove Japanese Knotweed, or contact us to get started today!

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