Japanese knotweed - Identification

Japanese knotweed is a distinctive plant and early identification is essential to prevent further contamination.

The weed assumes various states through the year which can make it difficult to identify.

To the untrained eye it can seem quite unassuming, even pleasant.

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Seasonal Features

Young knotweed shoot
The first signs of Japanese knotweed growth are distinctive red and purple shoots.

These are often accompanied by rolled back leaves which grow rapidly from the stored nutrients in the rhizome.

Stems with creamy white flowers
The stem resembles bamboo, though more green in colour with purple speckles. Inside, the cane has distinctive chambers that retain water and nutrients.

The leaves have pointed tips that extend from the stem in a zig-zag pattern. Later in the season, creamy-white flowers hang in clusters from the stalks.


As the first frost appears, the plant's leaves turn brown. During this period Japanese knotweed withdraws back into its rhizome.

The canes lose colour and turn into woody stalks which can take years to decompose.

New shoots can be found growing through the dead canes in the early Spring.