St. Patrick and Shamrocks

The English word "shamrock" is based on the Irish word "seamrog" (which means "little clover").  The shamrock associated with St. Patrick is a three-leaf clover which, according to legend, he used to explain the Trinity.  For example:  As a shamrock is one stem which happens to have three leaves, God is one God who happens to have three parts (Father, Son and Holy Spirit).

Since no contemporary evidence exists, linking St. Patrick to this teaching approach, no one can be sure whether he actually taught the Irish people in this way.