This is one of our unwelcome alien plants, found on saltmarshes and mudflats, on intertidal areas where it spreads widely. Up close it's an extremely pretty sight through a hand-lens with tiny feathery pale yellow flowers in 30cm long spikes. They bloom from July to September, the plant growing to about 1.5m high. The leaves are light green, very tough and narrow. It is a fast-growing non-native plant, a member of the family Poaceae.
I recorded this plant growing at Saltmills, Co Wexford in 2006 and photographed it at that time.
If you are satisfied you have correctly identified this plant, please submit your sighting to the National Biodiversity Data Centre