By historical definition, a four-leaf clover is not a shamrock. All shamrocks are three-leafed. Four-leaf clovers are rare in a garden since most clovers are three-leafed. So, if folklore holds and you want a bit of the "luck of the Irish," then go hunting for a four-leafed clover, not a shamrock.

The short answer: one small leaf. Shamrock, which comes from the Old Irish word “seamróg”, means “little clover” and describes a three-leaf clover. Since a four-leaf clover has four leaves, it’s not considered a shamrock. That small lucky leaf makes all the difference!

The shamrock is a symbol that we commonly associate with St. Patrick’s Day and with Ireland. It can be seen all over St. Patrick’s Day decor, representing the rebirth of spring. Sometimes, the shamrock is depicted as a four-leaf clover, but this isn’t quite accurate. Traditionally, a shamrock is a three-leaf clover.

A fourth leaf is where we get the luck from. The four-leafed clover, or “lucky clover”, is an uncommon variation of the three-leafed clover and is widely considered a symbol of good luck. Shamrock, or “seamrag” in Gaelic, means “little clover”, which is fitting because shamrocks and four-leaf clovers belong to the white clover plant family.

The four-leafed clover, or “lucky clover”, is an uncommon variation of the three-leafed clover, and widely considered to be a symbol of good luck. Because they are a mutation, they are rare, and not found in the same abundance as the shamrock, and thus, considered lucky. The traditional Irish symbol of a shamrock does not include the fourth leaf.