Finding a four leaf clover is pretty rare but if you happen to find a 5 leaf clover then you're even luckier since a 5 leaf clover is even more rare than a 4 leaf clover.
The 5th leaf that occurs on a clover is due to mutation and that makes it even rarer because mutation rarely happens with clovers.
So if you believe in the luck that 4 leaf clovers bring then you'll be even more lucky when finding a 5 leaf clover.