Japanese knotweed

(Fallopia japonica)

The most widespread form of knotweed, which is described in more detail in the knotweed overview, as well as in the History, Growth and Identification sections of this website. Distinctive identifiers are the young reddish/purple stems (petioles) that form into ‘zig zag’ shapes from node to node due to the alternate leaf structure.

Leaves are fairly smooth, mid-green in colour, with a characteristic straight back edge, giving the overall leaf a shield shape. Flowers are creamy-white and form in loose clusters (panicles) in late summer/early autumn. All Japanese knotweed plants growing in the UK are female and do not produce viable seeds. Japanese knotweed is also referred to in some sources as Fallopia japonica var. japonica. As stated above, it has previously been classified as Reynoutria japonica and polygonum cuspidatum. It appears to be traditional for knotweed species to be classified by several names at different times, as the following will show.

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