Only some nations have adopted national flowers: Egypt has the lotus; England, the rose; France, the iris, or fleur-de-lis; Ireland, the shamrock; Japan, the chrysanthemum; The Netherlands, the tulip; Scotland, the thistle; and Switzerland, the edelweiss. The national flower of Wales is the daffodil but the leek, the vegetable, is also considered a national emblem.
Canada has as its national symbol not a flower but the maple leaf. The United States has never adopted a national flower, but the states, as well as the District of Columbia, have all chosen state flowers.
See Wikipedia list of national emblems