Japanese Knotweed

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(Fallopia x bohemicum or F. x bohemica or Polygonum x bohemicum)
Quick ID:
  • Grows to heights of 6-10 feet
  • Stems are smooth, bamboo-like and stout
  • Stems are hollow, but may be water-filled depending upon soil moisture and time of year


  • Found in parks, gravel bars, along riverbeds, stream banks, rights-of way, and roadsides. It is also found in riparian areas and will move up river columns.

How It Got Here:

  • Originated from Asia and spread west for the last few hundred years (primarily by fragmentation)
  • 10mm of plant can re-grow to maturity.
  • Japanese Knotweed can propagate by fragmentation but not by seed like Bohemian.

Reasons for Concern:

  • Can invade and thrive in a variety of habitats with no natural predators or control mechanisms.
  • Japanese and Giant Knotweed have evolved into the Bohemian variety found in North America.
  • This species is now on both coasts to propagate by seed and fragmentation.   This likely explains the rapid progress observed in the Americas as opposed to the rather slow progression of the UK and Asiatic strains.  
  • Knotweed rapidly reproduces through seeds, rhizomes, and will move quickly down a riverbed and create one solid monoculture infestation.
  • Canes can sprout through 6 inches of concrete or asphalt and will damage roads & foundations to the extent they need to be replaced.