Today is the Feast of Saint David, the Patron of Wales. During a battle against the Saxons, David suggested to King Cadwallader that the Britons wear leeks in their hats to distinguish them from their enemies. They won the battle, and to this day, Welshman celebrate the victory by affixing leeks to their hats.
"I wear it for a memorable honour; For I am Welsh, you know, good countryman." Shakespeare "Henry V," Act 4 Scene 7