This unmistakeable plant came all the way to Ireland from S Africa. An annual, with prostrate or semi-erect stems and alternate, linear leaves sheathing the stems, it is the flower-heads which certainly gave it the name 'Buttonweed'. This is a member of the Asteraceae family but its ray florets are so tiny that it is the tubular disc florets which seem to make up the little yellow flowerheads. It's like a daisy without the petals. The bright yellow flowers (8mm across) are borne singly on long stalks and always face the sun from July to October. It is also known as Brass Buttons and Golden Buttons.
I spotted this plant growing in the grounds of Tintern Abbey in Co Wexford in 2008. I wondered if it had been planted and made enquiries to this effect. However the Office of Public Works, whose area of responsibility comprises Tintern Abbey, have assured me that it was not planted by 'man'. I photographed it in July 2008.
If you are satisfied you have correctly identified this plant, please submit your sighting to the National Biodiversity Data Centre