The shamrock is three-leafed old white clover (even though it's actually green) and the symbol of Ireland. The shamrock is an Irish Christian symbol of the Holy Trinity. It was St. Patrick who began comparing the shamrock and the Holy Trinity and thus the shamrock is associated with him too. It also appears on the city of Montreal, Canada's flag, representing the Irish population as one of the four major ethic groups that made up the population when the flag was designed. A four-leaf clover is a shamrock with an extra leaf, considered to be lucky especially if found accidently. Legend also says that if a lady hangs a four-leaf clover on her door, the next man to come through will become her husband. The fact is that generally every one in 10,000 clovers has four leaves. Each leaf of a four-leaf clover represents a different ideal: the first is for hope; the second is for faith; the third is for love and the fourth is for luck. Shamrocks can actually have many leaves. The record currently stands at eighteen. Botanists are still uncertain on whether extra leaves are caused by genetic mutations or through the environment that the shamrock is grown in. Therefore, it is not possible to cultivate four-leaf clovers but there are companies that clone and sell them.
Shamrock and four-leaf clover tattoos are very popular with those with Irish ethic roots. They are both seen as symbols of good luck as well. Four-leaf clover tattoos sometimes incorporate other lucky talismans such as rabbit's feat, horseshoes and dice.