Tree Killers: Japanese Knotweed
Return to our Tree Killers resource homepage here:
Tree Killers resource →
Name
- Common English name: Japanese Knotweed
- Other names: Asian knotweed, Japanese Bamboo
- Latin (scientific) name: Fallopia japonica or Polygonum cuspidatum
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
Biology
- 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
More information
Photo Gallery:
Follow us on social media to keep up-to-date.