Identification

  • It is rhizomatous (produces underground stems) with distinctive hollow, bamboo-like stems that can grow to over 3m in height.
  • The mature canes are hollow and have a characteristic pattern of purple speckles.
  • During the winter the leaves die back and reveal orange/brown woody stems.
  • The underground rhizomes are thick, woody and when broken reveal a bright orange-coloured centre.
  • The rhizomes extend laterally for 7m away from the parent plant. Small fragments of rhizomes can resprout and the principal means of spread is through the deliberate or accidental movement of rhizome fragments or cut stems.

The following images help to show features to identify Japanese knotweed. All images are copyright to John Early and cannot be used without permission.

Japanese knotweed shoots emerging next to mature canes

Japanese knotweed shoots emerging next to mature canes

Japanese knotweed stems close up during the summer

Japanese knotweed stems close up during the summer

Japanese knotweed late summer flower (August onwards)

Japanese knotweed late summer flower (August onwards)

Japanese knotweed orange rhizome

Japanese knotweed orange rhizome

 

Japanese knotweed winter canes

Japanese knotweed winter canes

Japanese knotweed shoots emerging from disturbed ground where knotweed was growing

Japanese knotweed shoots emerging from disturbed ground where knotweed was growing

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Japanese knotweed winter canes close up

Japanese knotweed winter canes close up

 

Japanese knotweed leaf shape. Note the zig zag arrangement along the side shoot.

Japanese knotweed leaf shape. Note the zig zag arrangement along the side shoot.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Read more about how to identify this species.