Flanders poppy

Due to the extent of ground disturbance in warfare during World War I, corn poppies bloomed in between the trench lines and no man's lands on the Western front. Poppies are a prominent feature of "In Flanders Fields" by Canadian Lieutenant Colonel John McCrae, one of the most frequently quoted English-language poems composed during the First World War. During the 20th century, the wearing of a poppy at and before Remembrance Day each year became an established custom in most western countries. It is also used at some other dates in some countries, such as at appeals for Anzac Day in Australia and New Zealand.

http://en.wikipedia.org/wiki/Papaver_rhoeas