Tuesday, March 01, 2005 +

Feast of Saint David

1 March

“On Saint David's day, March 1, inevitably under a dreary northern sky, the Welsh wear the green and pungent leaves of leeks pinned to their lapels. This tradition dates from a hundred years after the death of Saint David, when a detachment of Welshmen at the Battle of Agincourt, finding themselves so plastered with mud that they could not tell friend from enemy, picked leeks growing in a nearby garden and wore them as insignia. Those translate now into the miniature gold leeks worn on the khaki berets of Welsh Guardsmen today, and by my great-grandfather in 1916.”
—Paul Watkins, “Saint David, Patron Saint of Wales,” in Paul Elie, ed., A Tremor of Bliss: Contemporary Writers on the Saints (New York: Harcourt Brace, 1994).

It appears that other sources cite other battles.