The poppy is the recognized symbol of remembrance for war dead in Canada, the countries of the British Commonwealth, and the United States. The flower owes its significance to the poem In Flanders Fields, written by Major (later Lieutenant-Colonel) John McCrae, a field surgeon in the Canadian artillery, in the midst of the Second Battle of Ypres, in Belgium, in May 1915.
The poppy references in the first and last stanzas of the most widely read and oft-quoted poem of the war contributed to the flower's status as an emblem of remembrance and a symbol of new growth amidst the devastation of war. via
IN FLANDERS' FIELDS by John McCrea
In Flanders fields the poppies blow
Between the crosses, row on row,
That mark our place; and in the sky
The larks, still bravely singing, fly
Scarce heard amid the guns below.
We are the Dead. Short days ago
We lived, felt dawn, saw sunset glow,
Loved, and were loved, and now we lie
In Flanders Fields.
Take up our quarrel with the foe:
To you from failing hands we throw
The torch; be yours to hold it high.
If ye break faith with us who die
We shall not sleep, though poppies grow