Giant Knotweed

Giant Knotweed is a species of Fallopia native to north eastern Asia, northern Japan and the far east of Russia it was introduced to Ireland by gardeners and now resides in most counties across Ireland.  


It is identified by the leaves which are some of the largest in the family, up to 15–40 cm long and 10–28 cm broad.

Giant knotweed is a herbaceous perennial plant. The flowers are small, produced on short, dense panicles up to 10 cm long in late summer or early autumn and grows to 4 meters high.


It is invasive and the impacts on the environment are significant.


The species is closely related to the Japanese knotweed - Fallopia japonica, and can be distinguished from it by its larger size with a  smooth edged, elongated heart-shaped leaf, with a slight wavy, crenate margin. 

Giant Knotweed has a wide-ranging root system, which can extend up to 3m in depth and 7m in all directions.


These can pose a serious threat to construction works and have devastating consequences to building structures, foundations and drains.

Structural damage caused by untreated Giant knotweed can cause tens of thousands of euro's to rectify.

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