It is because it is said that St. Patrick used it to explain the Trinity. He taught them that the Father, Son and Holy Spirit are one, and used the shamrock as a way of doing so, by showing it had 3 leaves but is one plant. It has since become one of the symbols of Ireland. So it is among those that appear on St. Patrick's Day.
A shamrock.
St. Patricks day! About 65% of the people at the St. Patricks day parade are Irish!
No, they are not only the shamrock: the Father, the Son and the Holy Spirit. Must be an American thing. "Luck of the Irish" etc.
The shamrock is most commonly associated with Ireland. It is a symbol of Irish culture and is often used to represent the country, especially on St. Patrick's Day.
The wearin' of the green...(a shamrock).
Saint patricks day
st patricks day
Oh you know, Irish stuff.
The Irish do.
Saint Patricks day.
I believe that it is the luckiest day to be Irish.
The Catholic and Protestant Irish often get into fights on St Patricks day.