A Shamrock is a bright green spring clover–the species is unclear….but probably common clover (Trifolium dubium) or white clover (Trifolium repens), just like your garden variety pony eats. The shamrock has been an instantly recognizable symbol of Ireland for a long time…or maybe not. Anecdotally Saint Patrick utilized the humble plant in order to explain the nature of the trinity to his nascent flock in the fifth century AD (in which case they were the only people to ever understand the incomprehensible mystical unity-yet-separation of God, Jesus, and the Holy Ghost).
More realistically, however, the association between the Irish and the plant is less clear. English sources from the 16th century mention Irish “shamrocks”– but largely in the context of destitute Irish eating field plants (once again the species in unclear, but it seems like it might have been wood sorrel or watercress). Edmund Spenser, who lived among the Irish (and hated them), wrote approvingly of seeing Irish people starving to death after a failed rebellion left them with no crops, “…they spake like ghosts, crying out of theire graves; they did eat of the carrions …. and if they found a plott of water cresses or shamrockes theyr they flocked as to a feast for the time, yett not able long to contynewe therewithall.” Of course, since Spenser reportedly starved to death himself he might have later found occasion to eat these harsh words (literally and figuratively).
All of this leaves (!) us no closer to understanding how the shamrock became so indelibly affiliated with the Irish. Increasingly it seems like it may be a connection which was made in the early modern era. However, pre-Christian Irish were known to hold the number 3 in greatest esteem. Certain Celtic deities had three aspects and the number 3 was obviously sacred. This is strongly reflected in pre-historic Celtic art. Some of these mystical gyres and whirls do indeed look oddly like shamrocks…so you will have to judge the merit of the little green plant on your own. In the mean time I am going to head down to the great Irish restaurant, McDonalds, and see if I can find a shamrock shake. Usage maketh the myth and by that token there is nothing more Irish than a three-leafed clover.
It should additionally be noted that in the modern world, “shamrock” has become the name of a bright Kelly green color. You may even see it today reflected in spring foliage, or jaunty banners, or on a furtive leprechaun or two (although, leprechauns traditionally wore red until they became standardized and bowdlerized in the early twentieth century). Have you ever wondered whether everything you know if blarney made up by marketers less than a lifetime ago?
Wha…? That is clearly a four-leaf clover! Curse you infernal tricksters!