As a kid I would sift through the grass in search of a four-leaf clover to hold onto. They certainly are few and far between...
"The Shamrock is a three-leafed clover that grows in Ireland. A common image in Celtic artwork, the shamrock is found on Irish medieval tombs and on old copper coins, known as St. Patrick's money. The plant is also reputed to have mystic, even prophetic powers-- for instance the leaves are said to stand upright to warn of an approaching storm.
Legend has it that St. Patrick used the shamrock in the fifth century to symbolize the divine nature of the trinity when he introduced Christianity to Ireland."