Lucky Shamrocks and Clovers

Many people celebrate St. Patrick’s Day by wearing green clothes, eating and drinking green-colored foods, and even seeking out and  bringing a “lucky plant” into their home or garden. Yes, it’s shamrock season! Whether you get your hands on the plant itself, or simply draw or wear one on your being, you should know the difference between a shamrock and four-leaved clover, because today they’re often not the same thing.

Walk into a garden center this time of year, and you’re likely to see little pots of lush, three-leaved plants labeled “shamrock.” That term comes from the Gaelic word seamrog, meaning “small clover”—a plant in the genus Trifolium. Yet if you look closely at the label of that “shamrock” in the store, it’s likely labeled as genus Oxalis, a type of wood sorrel. Both plants look similar in one way—they each have three leaves per stem; although the leaves of a “true clover” are more oval in shape than Oxalis, which has heart-shaped leaves. The biggest difference is in their blossoms. Pictured at the top of this article is Oxalis—notice the trumpet-shaped flowers. Here’s what Trifolium blooms look like:

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Some people don’t think it’s lucky to find clover Trifolium growing in their lawn, but it brings good fortune to the plants around it, as well as to bees. True clover is a legume, a type of plant that fixes nitrogen in the soil. It’s a natural soil-fertility builder. And bees get buzz-y when white clover (the kind often found in lawns) is in bloom—it’s nectar-iffic to them! (Check the next batch of honey you buy; if it’s “clover honey” you’ll understand another reason clover is important to people.)

So where does a four-leaf clover come into the picture? Sometimes one can, indeed, find a four-leaved clover growing amidst typical three-leaved stems. Of course, this rarity makes it a lucky discovery; the Druids in Ireland believed them to be a sign of luck, and the Celts in Wales thought them to be a charm against evil spirits. The beliefs passed through generations and transcended cultures.

Botanists debated for decades about what caused the mutation: genes or environmental factors? Both, as it turns out. In 2010, the gene that turns three-leaf clovers into four-leaf was discovered, and that environmental conditions can have an influence on the gene.

It’s estimated that you have a 1 in 10,000 chance of finding a four-leaf clover. But the odds are much better that bees will find—and benefit from—clover allowed to grow in your lawn. And what’s lucky for bees is good for all of us.

Wendy Perkins is a staff writer for San Diego Zoo Global.