Clover, also known as trifolium or trefoli, is a genus of about 300 species of plants in the herbaceous pea family Fabaceae. Clover grows all over the world and is generally recognized by its trifoliate leaves and thick spikes of tiny red, purple, white or yellow flowers. Shamrock, the traditional Irish symbol, is actually a young clover. The Irish believe that the shamrock was invented by Saint Patrick as a symbol of the Holy Trinity. Clovers sometimes have four leaves, instead of the typical three, and these rare examples of the plant are considered a sign of good fortune and luck.