Alfalfa, also known as clover and four-leaf clover, is a perennial herb of alfalfa in Leguminosae. Generally, there are only three small leaves, which are heart-shaped, and the darker part of the leaf heart is also heart-shaped. Among 100,000 alfalfa plants, you may only find one four-leaf clover, and the probability is about one in 100,000. Therefore, four-leaf clover is considered as a symbol of luck.