Japanese Knotweed


Name: Japanese Knotweed                                  Fallopia japonica


Timing: Late Spring to Autumn




  • Although quite attractive, this plant is ferocious and aggressive in growth, spreading quite rapidly.

  • It grows like Bamboo but its main secret weapon is its creeping roots.

  • It can reach over 2M tall flowering in late summer before shoots die back in winter to ground level.


  • It alone has caused damage to building and structures reducing house prices all over the country.


Life Cycle

The Shoots

Rhizomes branch out (the start of that extensive root network)and the first shot start to appear. Shoots look sturdy and are red/brown in appearance. They are are hollow apart from the nodes.


Growth Period

Leaves grow on alternating nodes (1 leaf per node) while the stem grows like bamboo. The nodes are growth points which enable Japanese knotweed to gain height.. The Network of rhizomes increases under the ground and more shoots may appear.

Mature Plant

Once mature little greenish-white flowers appear on the axil of the leaves. This occurs between July to September. Male and female parts appear on separte plants and seeds are rarely produced. 


Die back usually occurs from late September onwards. Leaves start to turn brown. Stems turn to a lighter brown and dry out becoming brittle. Stems last throughout the winter.

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