Japanese Knotweed

Japanese knotweed (Fallopia japonica) was recently found in Strathcona County.  This invasive plant is a prohibited noxious weed and is listed on Alberta’s Weed Control Act. 

Identification

  • Wide, oval-shaped leaves and smooth margins.
  • Tough stems that are difficult to break, although they are hollow in the centre.
  • At each node where the leaf comes out, there is a thin membranous cover, which makes the stem look almost like bamboo.
  • If it blooms, the flowers will be small and white, but clustered together to make a larger "spray" inflorescence.
  • The key difference between Japanese knotweed and ornamental knotweed are the tiny hairs on the underside of the leaf along the midrib.
Image showing the different ways to identify japanese knotweed
No parts of Japanese knotweed should be be grown as they spread rapidly by rhizome and sometimes by seed.  There is some difficulty in identifying these plants, as they look quite similar to an ornamental variety.  The knotweed family is a botanically confusing family where species often have two or three other names (synonyms) and there is hybridization between species.
Image of a Japanese Knotweed plant

Japanese knotweed, giant knotweed, and hybrid Japanese knotweed have been known to grow through foundations of houses, come up through concrete and pavement on roads and sidewalks, and are a serious concern in any high density, urban area such as Sherwood Park.  This plant spreads quickly by rhizome, so please check your yard for any plants that look similar to the photos on this page. 

For more pictures or identification help visit the Alberta Invasive Species Council’s website at www.abinvasives.ca

Let us know!

If you believe this plant is in your yard, please email a photo showing the stem and leaves of the plant to the email address below along with your contact information so we can follow up with you.

Further information:

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Last updated: Wednesday, December 06, 2017
Page ID: 48754