Native to Japan and China Japanese Knotweed was introduced to Europe as an ornamental garden plant in the 19th century. Unfortunately it very quickly established itself in the wild and spread rapidly and is now considered to be one of our most problematic invasive species. It is a common sight on waste ground and along waterways and roads, where it takes over and competes with native species.
What does it look like?
It is a green shrub with a hollow stem, reaching about three meters in height and grows in dense thickets. It has a small creamy white flower in late summer and dies back in winter leaving brown cane like stems on the ground.
Identification sheets can be downloaded at
Why does it cause problems?
What to do?
The most important thing to do if you discover Japanese Knotweed is NOT to spread it.
Japanese Knotweed can be eradicated effectively by the use of an appropriate herbicide applied by a competent person, however the process requires follow up treatment and the disposal of the plant material and treatment of contaminated soil needs also to be considered and requires a license.
Please report sightings to the National Biodiversity Data Centre: www.biodiversityireland.ie/projects/invasive-species/submit-sightings/ Once the sighting has been verified, it will be made available online through Biodiversity Maps for all to access.
The National Biodiversity Data Centre have produced a list of FAQ’s on Japanese knotweed that can be found here.