It's worn in the buttonhole of a lapel, so the name of this floral accessory is French for "buttonhole"
[DOC] [TLE] How to Wear a Boutonniere - The Art of Manliness [PAR] Jul 9, 2010 ... A simple flower worn on the lapel of a jacket is a gesture full of ... you wear a 
flower on your lapel when you have no buttonhole or the hole ... wearing a 
boutonniere, it's about realizing and showing that the little ...