By Discover and Share magazine of the Missouri Botanical Garden

Every March, many storefronts, restaurants, and homes turn green as Irish Americans celebrate their heritage through St. Patrick’s Day. 

Of course, many without Irish ancestry join in the celebration, too. During the St. Patrick’s season, the shamrock becomes a universal symbol of all things Irish. And rightfully so—the shamrock is the national plant of Ireland and holds a special place in Irish history.

The word “shamrock” comes from the Irish seamair óg, meaning “young clover.” The shamrock is closely tied to St. Patrick himself, Ireland’s patron saint, who is said to have used the shamrock as a visual to explain the concept of the Holy Trinity.

In addition to the plant’s roles in folklore and religious iconography, shamrocks have been used as an unofficial national symbol of Ireland. The Irish shamrock is typically shown alongside the rose of England, the thistle of Scotland, and sometimes the Welsh leek, all growing from a single stem. This iconographic use for the shamrock may be traced back at least to the outset of the Revolutionary War, when troops were transferred from Ireland to the colonies.

Beyond Ireland, the shamrock and related species, continue to play a significant role in modern agriculture, with use as a soil-improving cover crop, food for livestock, beekeeping, natural dyeing and even homeopathic medicine around the world.

Some shamrock traditions continue into modern times, too. To this day, Irish people traditionally wear sprigs of plants they identify as shamrocks, usually pinned to a lapel or hat, on St. Patrick’s Day in remembrance of the Saint’s teachings. A less commonly practiced tradition calls for the shamrocks to be “drowned” in a cup of Irish whiskey at the end of the day and, after the cup has been drained, tossed over the drinker’s left shoulder for good luck.

The “four-leafed clover” is another common symbol of good luck. This lucky clover, however, is actually distinct from the shamrock, though often confused with it. The presence of four or more leaflets in clover is usually due to a genetic mutation occurring at a rate of about 1 in 5,000 specimens. 

While the word “shamrock” brings to mind a simple image of a small, green, three-leaf plant, botanically speaking, the name does not refer to a single plant species. Species traditionally identified as shamrock are part of the Fabaceae or legume family.

In Ireland, the term “shamrock” is generally applied to a small-leaved clover, Trifolium dubium, or sometimes another close relative, the slightly larger white clover, Trifolium repens. All clover species are noted for their ability to affix nitrogen from the atmosphere into the soil through their roots. The nectar from their flowers is a favorite of bees, butterflies, and other beneficial pollinators. 

America has also looked beyond Trifolium and adopted Oxalis, a plant native to the Americas and South Africa, as its own version of the shamrock.

Oxalis is commonly sold in stores as a “shamrock” plant. You’ll likely see them on display around St. Patrick’s Day. Most varieties produce mounds of shamrock-shaped leaves, 4-12 inches tall, earning it the spot as America’s shamrock. 

The leaves of Oxalis can be deep purple, bright green, maroon, blue, or a combination of these colors. They produce flowers in shades of pink and purple or yellow and white. Its dainty flowers and vibrant foliage make it an attractive plant for home gardeners, especially for use in containers. 

Oxalis do best in part shade, preferring well-drained soil that is kept evenly moist. They will wilt if the soil is allowed to dry out, so it’s best to protect them from strong sunlight. Fertilize the plants regularly during the growing season. The plants are not reliably hardy in the Midwest, so should be moved indoors during colder weather, or treated as an annual during the summer. 

According to Dengarden magazine, the right way to grow shamrock from seeds is, first, to cool your seed packets in the refrigerator at least overnight, but preferably for 24 hours.

Then, fill a pot (one with drainage holes is preferred!) with high-quality potting soil and dampen the soil. This is perhaps best accomplished by allowing a pot with drainage holes to wick moisture from a bowl of lukewarm water.

Sprinkle seeds onto the surface of the soil and then press them gently into the soil. You don't want to cover them completely with soil.

And place the pot in a warm place with indirect sunlight.

Seeds should germinate and sprout within two weeks of planting but may take up to two months depending on the time of year and the climate.

Don't over-water your shamrocks! They want to be moist, not wet. Misting should do the trick, but check to make sure that the soil is consistently damp.

Once your clover has germinated and sprouted, their care is relatively simple. You want to do what you can to imitate the climate in Ireland, where this particular clover is most common. This means you'll want to start by providing them a spot to grow in where the temperature is warm (but not hot!) and where they receive indirect sunlight. 

Additionally, you'll want to mist, rather than watering, your shamrocks, as this will simulate the rain that they would get in the wilds of Ireland.