The Celtic harp is the official symbol of Ireland, but the three-leaf shamrock is the unofficial symbol, more widely recognized worldwide than any other. Though there are many species of clover, the shamrock is "white clover" or Trifolium repens, a flowering vine with white blossoms. The Gaelic word for shamrock is seamrog.
The earliest written mention of shamrocks is not until 1571, even though Saint Patrick's legendary use of a shamrock predates this by over a millennium. It is said that he preached to the pagan Celts by using the three-leaf clover to illustrate the Christian trinity of a united Father, Son and Holy Spirit. Since there is no written record of the Trinity legend until 1727, many suspect this to be an 18th century myth that has been backdated.
Whether the legends surrounding the shamrock are fact or fiction is hard to say today, but the shamrock was an important plant to the Druids prior to Saint Patrick. It was believed to have medicinal properties and its association with the number three had significant meaning in ancient numerology, in which three was a sacred number with mystical powers. The shamrock might even have been thought to have prophetic properties, as some say an upward direction of its leaves foretold grave weather. The Druids also believed the shamrock could ward off evil spirits.
Whatever its ancient associations, it's clear from more recent history that the shamrock continued to be a potent icon. It was held as a symbol of rebellion and independence from the British crown during the reign of Queen Victoria (1837-1901). So powerful was the sign of the shamrock that to wear it on a military uniform was a crime punishable by death. This oppression only emblazoned the shamrock in Irish culture and "the wearing of the green" became a point of pride. Shamrocks appeared on everything from clothing to masonry to personal affects. It transcended its spiritual roots, alchemizing into a political symbol of national pride.
Today the shamrock remains a quintessential icon associated with all things Irish. With its rich mythology and political history, it promises to remain an enduring and beloved symbol of the green rolling hills of Ireland.