When he was sixteen, St. Patrick was captured by Irish marauders who took him to Ireland where he was sold to a chieftain in Dalaradia. St. Patrick spent the next six years as a shepherd before escaping to Gaul where he received formal education in monasteries. This led to his ordination as a bishop.
St. Patrick then returned to Ireland as a missionary, where he spent the next forty years preaching, teaching, and baptizing while building churches, schools, and monasteries.
St. Patrick is believed to have died at Saul on March 17, 493 A.D. [* see ref. below]
The four-leafed clover is thought of today as lucky, which is explained superficially by reference to its rarity: one must be lucky to find one, therefore the clover itself is seen as bringing luck. The original symbolism probably goes back to the robust growth of the plant, which made it a symbol of vitality in general.
In medieval love poetry, couples often met or made love "in clover"; today, perhaps because of the importance of clover for pasturage, to be "in clover" means to live well, to be free of care, and to be prosperous.
Because clover, presumably as a reference to new life after resurrection, was at one time planted on graves, it also came to symbolize parting, often in combination with Roses (the symbol of love) and Violets (whose color is that of penance) ...
Christian symbolism finds green 'equidistant from the blue of heaven and the red of hell ... an intermediate and mediating color, soothing, refreshing, human, a color of contemplation, of the expectation of resurrection' [Heinz-Mohr]. Christ's Cross, as a symbol of the hope of salvation, was often portrayed as green, the Grail Emerald green ...
'The Emerald Isle' is Ireland, and green the color symbolizing the struggle for Irish
independence from Great Britain." [** see ref. below]
** "Dictionary of Symbolism", by Hans Biedermann, translated by James Hulbert, New York & Oxford: Facts on File, 1989/1992, pages 72 & 158.