Why Do We Wear Green on St. Patrick’s Day?

Every March 17, people in Ireland and around the world suddenly turn green. Shirts, hats, beads, and even rivers take on the color as part of the lively celebration of St. Patrick’s Day. This playful tradition—often called the “wearing of the green”—has become one of the most recognizable customs of the holiday. Yet the connection between St. Patrick, the patron saint of Ireland, and the color green is not as old as many people might assume.

Historically, blue was the color most closely associated with St. Patrick. Indeed, the saint was often depicted wearing blue robes, and “St. Patrick’s blue” was used in Irish heraldry (such as a golden harp against a blue background) and in the regalia of the Order of St. Patrick (a British chivalric order). The later connection with green may partly stem from one of the most famous stories about St. Patrick: his use of the shamrock to evangelize. According to legend, St. Patrick used the shamrock as a symbol of the Christian concept of the Trinity (three persons in one God) because of its three leaflets bound by a common stalk. Over time the shamrock became linked with both the saint and Ireland. Traditionally, the Irish have worn shamrocks in their lapels for St. Patrick’s Day, and the trifoliate leaves came to be regarded as a national emblem.

By the 18th and 19th centuries green had also begun to symbolize Ireland more broadly, inspired in part by the island’s famously verdant landscape—the source of its nickname, the Emerald Isle. The color became closely associated with Irish nationalism and with the country’s Roman Catholic majority, appearing in political songs, movements, symbols, and book covers that celebrated Irish culture and independence. For example, in the modern tricolor flag of Ireland, adopted in 1937, green is said to represent Roman Catholics. (Given that the orange of the flag represents Protestants and is associated with unionism, wearing orange on St. Patrick’s Day may be understood as a political statement in Ireland.)

As celebrations of Irish identity grew, especially among Irish immigrant communities abroad, green gradually became the color most strongly connected with St. Patrick’s Day. Modern festivities often feature other green-themed elements as well—including decorations, foods and beverages, and even landmarks such as the Chicago River, which is famously dyed green for the occasion.