Four-Leaf Clover Science: The Lucky Genetic Anomaly Behind The St. Patrick's Day Icon

If you find a four-leaf clover this weekend, count your blessings, but don't thank a leprechaun -- thank genetics.

The first half of the four-leaf clover's scientific name, Trifolium repens, means three-leafed. But an estimated one out of every 10,000 clovers is four-leafed. While the traditional St. Patrick's Day shamrock usually has three leaves, one for each member of the Holy Trinity, the four-leaf clover's superstitious associations with luck have made it the stuff of legend.

In 2010, scientists from the University of Georgia examined the DNA of the white clover -- the kind most commonly associated with St. Patrick's Day -- and discovered which genes influence the shape and color of the plant's leaves. One of the newly discovered genes can produce a four-leafed clover, but it's usually suppressed by another gene that controls the plant's three-leafed trait. The scientists published their work in the journal Crop Science.

So, that four-leaf clover that you spied in the garden? It likely got that way thanks to a mutation that weakened the gene that controls the three-leafed trait's ability to mask the four-leaf gene. There's also some interaction between both genes and various environmental factors like soil pH, temperature and pollution, but these interactions aren't fully understood yet.

Therefore, a four-leaf clover isn't quite magic, but it is something of a genetic rarity.

"This is a great time to be involved in white clover breeding" senior author Wayne Parrott said in a statement at the time. "We now have the tools to make it easier to breed important traits in this species, which has historically proven to be a challenging plant to work with. In addition, we can hasten the development of new white clover cultivars bred for a variety of uses by screening new generations of plants for traits of interest before they even reach the field trial stage, significantly reducing the time and resources needed for new releases of white clover."

And get this: Four leaves arent' necessarily the plant's limit. Five-leaf clovers turn up sometimes, and the Guinness world record for most leaves on a single clover stem is 56. The hydra-like clover was discovered in 2009 by Shigeo Obara in Hanamaki City, Japan. Obara, a retired crop researcher, specialized in breeding clovers and previously set records in 2008 and 2002, with his 21-leaf and 18-leaf clovers, respectively.

The clover isn't just an ornamental plant, or a St. Patrick's Day decoration. The Trifolium family -- a group that includes more than 300 species -- is a vital crop for farmers with many recommending features. It grows abundantly in a wide range of climates and soils, and it can be fed to livestock or used in compost -- and clover flowers provide one of the main sources of nectar to honeybees.