Japanese Knotweed

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Scientific Name
Fallopia Japonica

Identifying Characteristics

  • Resembles bamboo
  • Capable of reaching 1-3 meters in height
  • Stems has a bamboo-like appearance
  • Stems are round, reddish-purple, and smooth
  • Leaves are ovate with a flat base and pointed tips, reaching 3-6 inches long and 2-5 inches
  • Flowers are greenish-white
  • Fruits are small and white with wings that help to disperse seeds to new sites
  • Seeds are brown and shiny

Last Seen
  • Native to eastern Asia
  • Can be found in southern and eastern areas in Ontario where it grows in gardens, along roadsides, near old buildings and/or former building sites

First Offence and Known Accomplices

  • First introduced in the 1800's
  • Used as an ornamental species and planted for erosion control

Crimes Committed

  • Difficult to control
  • Spreads very quickly
  • Creates dense thickets that trouble wildlife habitats
  • Persistent plant with aggressive root system that can break through concrete and asphalt
  • Large population; able to survive floods & cold winters and recolonize areas
  • Can grow along riverbanks, where pieces of roots break off and flow downstream to start new populations
  • Competes with other native plants
  • Leaves thick layers of decomposing stems and leaves on the ground making it difficult for native plants to grow

Attempts at Capture

  • Due to its ferocious growing rate, it was extremely difficult to control
  • Control agents are brought over from the original habitat
  • Bugs are unable to attack invasive plant due to different climates
  • Ontario works with other provinces, the federal government and American governments to prevent spread of invasive plants


  • Fishing, hunting, forestry, tourism and agriculture can all be affected by this aggressive plant
  • Every year, invasive plants cost the agriculture and forest industries about $7.3 billion
  • Fighting & preventing the spread of invasive species is extremely expensive
  • Removing plants from highways and gardens is very difficult due to its ferocious root system