1. Shamrock is a symbol of Ireland
2. Saint Patrick, Ireland’s patron saint, is said to have used it as a metaphor to explain the Christian Holy Trinity
3. In pagan Ireland however, three was a significant number and the Irish had many triple deities
4. Shamrock is the diminutive of the Irish word seamair óg and simply means “young clover”
5. But what is it?
- At most times, Shamrock refers to either the species Trifolium dubium (lesser clover, Irish: seamair bhuí) 
- or Trifolium repens (white clover, Irish: seamair bhán).
- However, other three-leaved plants—such as Medicago lupulina, Trifolium pratense, and Oxalis acetosella—are sometimes called shamrocks
6. By the end of the sixteenth century the shamrock had become known to English writers as a plant particularly associated with the Irish, but only with a confused notion that the shamrock was a plant eaten by us.
7. It was taken up as an emblem by rival groups during the turbulent politics of the late eighteenth century.
- On one side were the Irish Volunteers, local militias in late 18th century Ireland, raised to defend Ireland from the threat of French and Spanish invasion when regular British soldiers were withdrawn from Ireland to fight in America.
- On the other side were nationalist groups, such as the United Irishmen.
8. The shamrock regularly appeared (in the 19th century) alongside the rose, thistle and (sometimes) leek for Wales in British coins such as the two shilling and the crown, and in stamps.
9. It also appeared on many buildings in Ireland as a decorative motif in that time.
10. It is currently used in the emblems of many state organisations, both in the Republic of Ireland (e.g. IDA Ireland) and Northern Ireland (e.g. PSNI)
11. In the early 1980s, Ireland defended its right to use the shamrock as its national symbol in a German trademark case, which included high-level representation from then Taoiseach Charles Haughey
12. It has become a tradition for the Irish Taoiseach to present a bowl of shamrocks in a special Waterford Crystal bowl featuring a shamrock design to the President of the United States in the White House every St. Patrick’s Day – as we saw yesterday.
13. This goes back to 1952 when the Irish Ambassador sent shamrock to then US President Harry Truman