Initiative continues to control invasive Giant Hogweed in Limerick river basin

A MAJOR seven-year initiative to control the invasive Giant Hogweed plant has been making significant progress across the Maigue catchment area, focusing on the River Loobagh, Morning Star, and sections of the Maigue River.
Led by the Maigue Rivers Trust, a registered environmental charity based in County Limerick, the project aims to significantly reduce Giant Hogweed populations by targeting the seed source upstream. The Trust has prioritised manual removal methods to control the spread while minimizing the use of chemical treatments.
Thanks to ongoing support from Limerick City and County Council (LCCC) and the Local Authority Waters Programme’s Community Water Development Fund, control works have continued effectively on the Morning Star River.
Over the years, each season has seen a steady decline in the number of flowering seed heads and juvenile plants, with several areas showing no regrowth of Giant Hogweed in 2024. The River Loobagh and Morning Star infestations are now considered under high-level control.

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Building on this success, efforts have now focused on the more heavily infested River Maigue, especially near the village of Bruree. The source of the infestation in this river was identified as the Loobagh River, which is now free of infestation.
Engagement with local landowners and stakeholders remains vital, as access to riverbanks is key to ongoing success.
In conjunction with Heritage Week, the Maigue Rivers Trust is coordinating an event to raise awareness about Giant Hogweed, including how to identify it and native lookalikes such as native hogweed and angelica, as well as control methods and future plans. The event is funded by the National Parks and Wildlife Service Local Authority Action Fund and Limerick City and County Council.
This project stands as a strong example of community-led environmental action, showing that invasive species control can be achieved effectively through dedicated manual work and local collaboration.
Ireland’s equable climate suits Giant Hogweed perfectly as it favours the damp, open margins of riverbanks where its seeds can readily disperse downstream as the plant can produce a large number of seeds.
Giant Hogweed is increasingly being recognized as one of the world’s most dangerous invasive alien plants due to its harmful effects on both people and the environment.
The plant produces a toxic sap found in all parts, which can cause severe burns known as lime disease when exposed to sunlight.
This chemical reaction poses serious health risks, prompting authorities to advise people to take precautions around the plant.
Beyond its toxic properties, Giant Hogweed’s massive size allows it to overshadow and outcompete smaller native plant species, eventually killing them off. Because its seeds are relatively heavy, they typically fall close to the parent plant, leading to dense clusters of hundreds of plants in a small area. This dense growth further disrupts native ecosystems.