Green ribbons and shamrocks have been worn on Saint Patrick’s Day since at least the 1680s.
The date is supported by historical evidence for Irish people wearing green ribbons and shamrocks as St Patrick’s Day symbols. It does not mean that every modern green tradition existed unchanged in the seventeenth century; rather, it marks the earliest known period cited for this custom.
Green became increasingly associated with Ireland over the following centuries. The Irish Catholic Confederation used a green harp flag in the 1640s, while the United Irishmen adopted green in the 1790s. Political songs and phrases such as “wearing of the green” helped connect the colour with Irish identity and resistance.
The shamrock has a separate religious association. Later tradition says Patrick used its three leaves to explain the Christian Trinity, but the earliest written version of that story dates to 1726. Historians therefore distinguish the documented use of the shamrock from the much later written explanation of why Patrick supposedly used it.
Blue is another common source of confusion: the Order of St Patrick, founded in 1783, adopted blue, but modern celebrations overwhelmingly use green.