While I had assumed that the boutonniere was simply a male version of The Bouquet, I was pleasantly surprised to find that it has it's own interesting and unique origin story!
During the age of knights, royalty and epic empires, a tradition was born that when a knight was riding into battle, or a jousting tournament, he would do so donned with a ribbon, scarf, flower or family crest of his lady love tied around the left arm of his suit of armor. This placed it closest to his heart (It's also safe to note, that with the majority of society being right handed, wearing it there also prevented their sword arm from becoming tangled at an inopportune time). This is where the saying "Wearing your heart on your sleeve" comes from as well!
Wearing a daily boutonniere was the norm among British and American men, often times picked from their wives gardens. While this practice began to fade in the 1960's as blue jeans, t shirts, and a more casual public dress code evolved - the wearing of a boutonniere is still reserved for more formal events, and has become a wedding tradition in it's own right.
Modern man has adapted these traditions by traditionally picking a flower from their bride's bouquet (or one that is harmonious with the bride's choice) and wearing it on their wedding day. Who knows, maybe as time progresses the daily boutonniere will make a comeback, as men's style swings back towards formal attire. Recently, I've even seen "functional boutonniere lapels" available as a custom option from many suit makers, a trend I first noticed when I ordered a suit from Indochino.
The daily style option not withstanding, the groom's party boutonnieres are, along with the bridal bouquet some of my favorite details.