TAHGDC: Japanese Knotweed

Introduced to the UK & Ireland in 1825, Japanese Knotweed was originally grown in gardens for it’s attractive & exotic appearance. It wasn’t until some years later that it came into focus that it was becoming an invasive plant and was threatening our countryside & waterways. Today Japanese Knotweed is high on the list of the most problematic plants in the country. It negatively impacts on native plants, as well as seriously undermining the structural integrity of roads, buildings and car parks.

So far this year, there have been just under 1,000 notifications to the National Biodiversity Data Centre of Knotweed in the country. As you can see from the map below, it is pretty much in every county in Ireland.

What should you do if you find Japanese knotweed?

Prevent further spread

If you do find Japanese knotweed on your property, you should try to prevent any further spread of the species. Do not strim, cut, flail or chip the plants. The remaining tiny fragments can regenerate new plants and make the problem even more difficult to manage. You should avoid digging, moving or transporting any soil which may contain potential plant material.


Japanese Knotweed itself, can be controlled, though it must be carried out with herbicides by a competent person. This requires proper planning as follow up treatments are usually required. Dead plant material must be disposed of correctly as well as treatment of contaminated soils. It is advised to prepare a management plan, and to get expert help before tackling any significant infestation of this species

All sightings of invasive species should be reported to the National Biodiversity Data Centre – online or via 051 306240 or invasives@biodiversityireland.ie.

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