Many of us remember hunting for that elusive “four-leaf clover” as a child, and we’ve all seen that green shamrock on St. Patrick’s Day. That brings us to today’s garden musings. Let’s talk about what a shamrock really is—and what it isn’t!
What Is a Shamrock?
The shamrock is a symbol that we commonly associate with St. Patrick’s Day and with Ireland. It can be seen all over St. Patrick’s Day decor, representing the rebirth of spring.
Sometimes, the shamrock is depicted as a four-leaf clover, but this isn’t quite accurate. Traditionally, a shamrock is a three-leaf clover.
Why three leaves and not four? According to legend, St. Patrick used a three-leaf shamrock to explain the Holy Trinity, with one leaf representing the Father, the Son, and the Holy Spirit, respectively. More recently, the four-leaf clover has also come to represent the Holy Trinity, with the fourth leaf symbolizing God’s Grace.
The True Shamrock
The word “shamrock” comes from the Irish word Seamróg, meaning “little clover” or “young clover,” but there isn’t a consensus on which species of clover is the “true” shamrock. In fact, there are a few plants that go by this nickname!
In Ireland, the plants that are most often associated with the name “shamrock” are the suckling clover (Trifolium dubium) and the white clover (Trifolium repens). Both clovers are native to Europe, but can be found throughout the world today. Their genus name, Trifolium, means “having three leaves”—an appropriate description!
According to Encyclopedia Britannica, a number of other similar-looking plants go by the name “shamrock”:
“Shamrock [refers to] any of several similar-appearing trifoliate plants—i.e., plants each of whose leaves is divided into three leaflets. Plants called shamrock include the wood sorrel (Oxalis acetosella) of the family Oxalidaceae, or any of various plants of the pea family (Fabaceae), including white clover (Trifolium repens), suckling clover (T. dubium), and black medic (Medicago lupulina). Wood sorrel is shipped from Ireland to other countries in great quantity for St. Patrick’s Day.”
As mentioned, “shamrock” can also refer to a plant called common wood sorrel (Oxalis acetosella). Wood sorrel looks very similar to clover, though the plants are not related. Tropical relatives of wood sorrel are often sold in stores as “shamrock” houseplants, since they’re better suited to the indoor environment than clover species are.
How Rare Is a Four-Leaf Clover? Why Are They Lucky?
As kids, we would spend hours searching for that lucky four-leaf clover—and often come home empty handed!
A four-leaf clover isn’t a special variety of clover; it’s just an unusual mutation of a three-leaf clover, but it’s a “lucky” symbol because it’s so hard to find. In fact, your chances of finding a four-leaf clover are 1 in 10,000! That’s where the luck comes in, apparently. According to popular lore, if you do find a four-leaf clover, giving it to someone else doubles your luck.
Traditionally, four leaves were considered lucky because they reflected the shape of a cross and were thought to be magical or sacred. Eve supposedly took a four-leaf clover with her when she was banished from the Garden of Eden, too.
In the Middle Ages, it was believed that carrying a four-leaf clover would enable you to see fairies, recognize witches and evil spirits, and be protected from the evil eye. Even dreaming of clover was supposed to bring good luck.
Superstitions aside, clover is valuable plant in many ways. Bees and other pollinators can’t resist its flowers (red clover is especially attractive to bumblebees), and the plants can be turned into the soil as green manure, too. Additionally, the roots host nitrogen-fixing bacteria that enrich the soil, and the plants are high-quality forage for many animals. The reasons to grow clover are endless!
The Value of Clover
In recent years, the idea of growing clover has been making a comeback. White clover (Trifolium repens) is well known for crowding out broadleaf weeds while growing harmoniously with grass. It will thrive in areas that are poorly drained or too shady for a conventional lawn, making it a great grass alternative.
As a legume, clovers have the ability to convert nitrogen into fertilizer using bacteria in its root system (a process called “nitrogen fixation”), practically eliminating the need for additional fertilization.
Despite today’s push for perfectly green lawns (which often involves a lot of chemicals), clover was not always viewed as a “weed.” The University of Minnesota Extension Service points out that, until relatively recently, it was standard practice to include clover seed in lawn seed mixes:
“Until the 1950s, clover was included in lawn seed mixes, as it was regarded as a prestigious lawn plant. It may be considered an attractive, low-maintenance ground cover that is soft to walk on, mows well and will fill in thin spots in a yard.”
Today, it seems clover is returning as a more eco-friendly lawn alternative. Since it is nitrogen fixating, it can supply its own nutrients to poor soil. Overseeding clover seed into your existing lawn is an easy way to establish a clover lawn. For lawns, the most popular is the white clover because it is relatively low growing, tolerates close mowing, and outcompetes weeds.
The False Shamrock
The last piece of the shamrock puzzle is a houseplant that also goes by the name “shamrock.” It usually crops up in grocery stores and nurseries around St. Patrick’s Day. This plant is not related to clover (the “true” shamrock), but is in the same genus as wood sorrel (Oxalis).
Image: Grocery store “Shamrock” (Oxalis) near St. Patrick’s Day. Credit: C. Boeckmann.
Oxalis are native to many regions of the world, but they’re most numerous in the tropics, which is where the houseplant species come from. Depending on the species, they can have green or purple leaves and white or pink flowers, and some cultivars, such as ‘Irish Mist’, have green leaves flecked with white. The whole plant is photophilic, meaning the leaves and flowers close up at night and open wide again in the morning.
Oxalis can be grown outdoors in the spring and summer in Hardiness Zones 6 to 11, but they also make for great houseplants year-round. They like bright, indirect light and tend to bloom in fall, winter, or spring.
Since they are grown from bulbs, let them dry out a bit between waterings to prevent rot. Don’t fret if your indoor Oxalis loses all its leaves in summer. It isn’t dead. It just needs a dormant period, so let it dry out and put the pot in a dark place until it decides to resume growth in a few weeks. As soon as new leaves appear, bring it into the light and resume watering. These plants are low maintenance and long lived.
Here are a few of the more popular Oxalis houseplant species:
- Sometimes called False Shamrock, Oxalis regnellii are native to South America. Pictured above, they have heart-shaped leaves instead of the clover’s oval-shaped leaves.
- Purple Shamrock (Oxalis triangularis) is a subspecies of O. regnellii that hails from Brazil. It has large, handsome, purple leaves and pale lavender-pink flowers.
- Lucky Leaf or Lucky Clover (Oxalis tetraphylla) is also known as four-leaved sorrel. Native to Mexico, it has four split green leaves with a dark maroon eye. The trumpet-shaped flowers of ‘Alba’ are white, ‘Iron Cross’ has pink flowers.
Oxalis houseplants all contain oxalic acid, the same chemical that makes rhubarb leaves and daffodils toxic. If eaten in large quantities, they can be poisonous to pets and small children, so don’t go feeding the leaves to your pet rabbit!
Now that you know the true identity of the shamrock, check out our St. Patrick’s Day page for more history and lore!