Wearing green

On St Patrick's Day, it is customary to wear shamrocks, green clothing or green accessories. St Patrick is said to have used the shamrock, a three-leaved plant, to explain the Holy Trinity to the pagan Irish. This story first appears in writing in 1726, though it may be older. In pagan Ireland, three was a significant number and the Irish had many triple deities, a fact that may have aided St Patrick in his evangelization efforts. Patricia Monaghan says there is no evidence that the shamrock was sacred to the pagan Irish. However, Jack Santino speculates that it may have represented the regenerative powers of nature, and was recast in a Christian context‍—‌icons of St Patrick often depict the saint "with a cross in one hand and a sprig of shamrocks in the other". Roger Homan writes, "We can perhaps see St Patrick drawing upon the visual concept of the triskele when he uses the shamrock to explain the Trinity".