According to legend, St. Patrick (the patron saint of Ireland who is honored on March 17) used the three-leafed shamrock as an aid for teaching about the three persons of the Trinity: Father, Son, and Holy Spirit. Although there is some debate over the specific plant that may have starred in those ancient lessons, today a shamrock is usually identified as a single sprig from a clover plant.
Clover is the common name for more than three hundred different species of plants, many of which are found within the genus Trifolium (the Latin name means "three leaves".) Although some people consider clover to be a nuisance in their lawns, it is actually a helpful plant that provides an important source of nectar for pollinators. It also reduces the need for artificial fertilizers by fixing nitrogen to the soil, and it helps reduce erosion.
White clover (Trifolium repens) is a wide-spread variety of clover that is often planted in pastures along with an assortment of grasses to provide forage for livestock. White clover is the variety most commonly associated with four-leafed specimens.
The "lucky" four-leafed clover is thought to result from a genetic mutation, although some scientists think that environmental or chemical factors may also be involved. According to "Four-leaf Clover," by Meghan Rose Donnelly, about one in every 10,000 clovers has four leaves.
The original version of this article appeared in the March 2016 issue of Observations: A Pier Press® Newsletter. You can access the archived issue here, and if you're not already a subscriber, click here to sign up. It's free.