JAPANESE KNOTWEED (Fallopia japonica)

 

Courtesy of  UK Environment Agency C.o.P.

Of the land based invasive plant species, Japanese Knotweed, and its hybrids, probably pose the greatest threat to our habitats and environment. This is due to its ability to spread rapidly and to outcompete our native flora. It has the ability to grow through tarmacadam, floors and walls, and plants can regenerate themselves from tiny fragments of stem or rhizome. Because of the structural risk it poses, its eradication from development sites in the UK and Ireland is required by law, and in Ireland, the 2011 Regulations strictly control the movement of both the plant itself and soil which is contaminated with plant material. Controlling and eradicating Japanese Knotweed can be a very difficult and expensive process. It has been suggested, for example, that the final cost of its removal from the London Olympics Site alone, amounted to nearly STG£70m.

  

Extract from the Non Native Species Secretariat Identification Sheet for Japanese  Knotweed

 

Originating in Eastern Asia, Japanese Knotweed was first introduced into the UK in the late 1800’s where it was prized as an ornamental “exotic” plant. It is most likely that it made its way to Ireland by similar means and at around the same time. It is a herbaceous perennial, with bamboo like stems that can grow up to 2 – 3m in height and has an extensive system of rhizomes. Its preferred habitats include urban areas, waste ground, roadside margins and river banks. Along rivers it can cause significant bank erosion, resulting in its easy spread downstream. Dispersal is typically by deliberate or inadvertent human activity, and by material being washed downstream during flooding. Typically Japanese Knotweed does not produce seed but can hybridise with other species of Fallopia.

 

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