Tree Killers: Japanese Knotweed

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  • Common English name: Japanese Knotweed
  • Other names: Asian knotweed, Japanese Bamboo
  • Latin (scientific) name: Fallopia japonica or Polygonum cuspidatum

Threat type

150x150 plants

History in Canada

  • introduced from eastern Asia to North America in the late 1800’s as an ornamental and for erosion control
  • still available from nurseries
  • established from southern Ontario to Newfoundland and in Manitoba and southern British Columbia


  • herbaceous, shrub-like perennial with large heart-shaped leaves 10-15 cm long (4-6 in)
  • belongs to the Buckwheat family
  • clusters of creamy-white flowers appear in late summer in upper leaf axils
  • the hollow stems have raised nodes but it is not related to bamboo which is in the Grass family
  • stems can grow to 3 m tall (10 ft)
  • reproduces mainly by vigorous creeping rhizomes that can form large dense patches
  • prefers open woods, floodplains, and forest edges but can tolerate a wide range of conditions
  • very persistent and difficult to remove once established

Impact on Trees

  • grows in open woodland, forest openings, and forest edges
  • dense patches suppress native tree seedlings

What can be done to control this tree killer?

  • cutting stems followed by herbicide application to the cut stems
  • herbicide application to the entire plant
  • digging up entire root system
  • several years of control may be needed since the seeds are unaffected by the above methods and rhizomes may re-sprout

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