The shamrock (typically Trifolium dubium or Trifolium repens) is the recognized national flower of Ireland. It is closely associated with St. Patrick, who allegedly used its three leaves to explain the Holy Trinity.
The yellow rose has no official status in Ireland. It may appear in gardens or as a cultivar name, but it does not represent the nation.
The shamrock appears on the badge of the Irish Defence Forces, the national airline Aer Lingus, and countless souvenirs, making it the enduring botanical emblem of Ireland.