Legends recount that Patrick, who was to become the country’s beloved patron saint, used the common three-leaf clover to explain the trinity. Most likely, however, people’s fascination with this humble green plant predates recorded history. Europe’s ancient Druids, for whom three was a sacred number imbued with great power, are believed to have revered the shamrock.

There's disagreement as to the identity of the true “shamrock”, with many choosing various types of ground clover. Some even make a claim for the three-leafed Oxalis species. In an attempt to settle the matter, E. Charles Nelson, Director of the Irish National Botanic Gardens, surveyed citizens throughout Ireland in 1988, asking them to send in samples of shamrocks. Although some 35% of Irish chose Trifolium repens, or White clover, the majority--over 50%--selected Trifolium dubium or Lesser clover. Both species are common throughout Europe.

The Latin name "trifolium" or "trefoil" means "three-leafed". "Shamrock" itself ultimately derives from the Irish word for clover, seamair. The diminutive form, seamróg, refers to a small or young clover.

Trifolium repens
Trifolium dubium

Irish botanist Caleb Threlkeld noted the association of the Trifolium and St. Patrick in a 1726 treatise on native Irish plants:

“This plant is worn by the people in their hats upon the 17. Day of March yearly, (which is called St. Patrick's Day.) It being a current tradition, that by this Three Leafed Grass, he emblematically set forth to them the Mystery of the Holy Trinity.”

The shamrock was eventually tied not just with St. Patrick, but with the Irish people as a whole. In the late 1700‘s, various local militias adopted the shamrock as a standard. During the Irish Rebellion of 1798, the revolutionary Society of United Irishmen identified themselves by their green clothing and ribbons. In this turbulent era, such “wearing of the green" could lead to imprisonment or even death. The 1801 Act of Union between Ireland and Britain established the shamrock as an official national symbol, found on Irish stamps, coins and public buildings.

Since that time, the shamrock’s popularity has only continued to grow. Particularly during the Victorian age, shamrocks were often reproduced on postcards and regarded with sentimental fondness, as in the poem “Oh the Shamrock” by Thomas Moore:

Where'er they pass,
A triple grass
Shoots up, with dew-drops streaming,
As softly green
As emeralds seen
Through purest crystal gleaming.
Oh the Shamrock, the green immortal Shamrock!
Chosen leaf
Of Bard and Chief,
Old Erin's native Shamrock!


ImageGrowing the three-leaved White clover (Trifolium repens) in American lawns is easy. In fact, say George and Becky Lohmiller of the Old Farmer’s Almanac, lawn clover (also called Ladino or Dutch clover) has come back into favor as gardeners become increasing aware of the dangers of herbicides. Clover is drought-resistant and blends well with most lawn grasses, while helping to prevent establishment of broadleaf weeds. Because it’s a legume, clover can convert nitrogen into fertilizer, thus reducing the need for additional lawn food. Its small, pinkish-white flowers provide nectar for beneficial insects like butterflies and bees.
Although it's rare, clover plants do occasionally produce four leaves instead of the normal three. The rogue fourth leaf is often much smaller than the others. This is likely caused by mutation, according to the website Biojournalism.com. With the odds of four-leaf clover occurrence at approximately 1 in 10,000, it's little wonder that finding one is reputed to be good luck!

Photo Credits:
Thumbnail by kahunapulej
Trifolium dubium by DG member Floridian
Trifolium repens by blumenbiene
Shamrock image in the public domain
Clover and bee by Cathie Bird
Four Leaf Clover by Ole Husby

Resources and More Information:

History.com: St. Patrick’s Days Symbols and Traditions

BBC News: The Truth Behind the Shamrock

Dublin City Public Libraries: Threlkeld Shamrock
Old Farmer’s Almanac: Clover Comeback

Biojournalism.com: The Science of a Lucky Charm -- Four-Leaf Clovers