Not an invasive species but a noxious weed
Each year the Biodiversity Project receives a number of queries on the issue of Ragwort. Ragwort is a native wildflower that is a member of the Asteracecea (Daisy) family. The plant grows in profusion along roadsides, disturbed ground and un-managed grasslands. It is a very attractive flower and is beneficial to many insects especially the Cinnibar moth caterpillar for which it is the food plant.
However, when eaten in large quantities the plant is toxic to many animals including Horses and Cattle and so it is classified as a Noxious Weed and under the Noxious Weeds Act of 1936, land owners and occupiers are obliged to remove the weed from their property.
The Department of Agriculture, Food and the Marine has useful guidelines on the control of Ragwort which you can view below . Further information on Ragwort and other noxious weeds may be found on their website – DAFM website
Ragwort is not harmful to humans, cats or dogs.