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Japanese Knotweed - Fallopia japonica

Terrestrial, along watercourses, transport routes and infested waste areas.

Japanese knotweed is a threat to infrastructure and has no natural enemy, so it is dominant within native ecosystems.

The plant is currently found throughout Ireland.

What does it look like?
Japanese knotweed is a tall plant, growing up to 3 metres in height. The leaves are oval and grow in a distinctive zigzag pattern up the plant stems. Creamy white flowers appear in late summer and early autumn.

The plant grows up to 10 centimetres a day and can reach between 2 and 3 metres in height in the summer. Japanese Knotweed can colonise new areas with vigour and rapidity and outcompetes native plant species. It is very damaging to infrastructure as it can grow through tar macadam and concrete. Japanese Knotweed can act as a barrier in important wildlife migration corridors. 

Where is it originally from?

What can you do?
Cutting down the plant can actually lead to a further spreading of the species so care must be taken.Visit the Invasive Species Ireland website to find out more and to report sitings. See the Invasive Species Ireland Best Practise Guide for information on how to manage Japanese Knotweed:

©2007 Department of the Environment, Heritage and Local Government