Query: What is a shamrock? Why is a four-leaf clover lucky?
Context: A shamrock is a three-leaf clover and the national flower of Ireland. Four leaf clovers are lucky because they are VERY hard to find. They say you can search clover patches for a thousand years and never find one. The truth is that the four-leaf clover is a rare variation of the common three-leaf clover. You have about a 1 in 5000 chance of finding a four leaf clover. [source]