What does green on the Ireland flag represent?

The Green stripe the nationalist tradition, the Orange represents unionists and the white stripe symbolizes the peace between them. The orange colour is associated with the Protestants in Ulster and those that derived from William III who defeated the Irish Catholics at the Battle of the Boyne in the late 1600s. It was included in the Irish flag in an attempt to reconcile the Protestants with the Irish independence movement.
While it may not represent anything officially according to the constitution of the country, it is sometimes said that the green represents the Gaelic tradition of Ireland.