Originally, the button hole on a lapel had a functional purpose. That purpose was for the button on the underside of the opposing lapel, which was used to button the coat up all the way to protect against cold weather. The function has evolved over the years and has been used in various ways.
The Milanese button hole, or the Asola Lucinda, is iconic and typically the most easily recognized type of button hole. This type is whip-stitched, which is why tailors rarely make the effort to include them on suits of today. They are more expensive to sew and require more effort, as they present a tight and clean appearance on the suit. The silk thread for these is wound around the gimp, rather than knotted. This shows any small mistake, since it requires constant tension to be done evenly. For those hoping to add distinct character to their suit, however, the addition of a Milanese button hole can be a good choice.
Uses for the Button Hole Today
Because the button hole is not used for its originally intended function, it is now typically called a boutonniere, a french term for button hole. It is also utilized mostly to add character to the suit, as it can hold a small grouping of flowers or a pin that says something about the suit wearer. Avoid using pins if possible, however, as the pin can pull threads lose or otherwise cause damage to the lapel of your suit.
When it comes to flowers in the boutonniere, a discrete loop is commonly sewn behind the lapel to hold the flowers in place when they are pushed through the button hole. This eliminates the need for a pin to secure them and still holds them there so the wearer need not be concerned about them while they are otherwise engaged.
If you are attending a formal event, opt for red or white flowers through your boutonniere. Meanwhile, informal events allow for more flexibility in color and variety of the flowers you wear. If you choose to wear a pocket square while wearing flowers, make sure to match the shade to the flower.
Flowers and pins (if you so choose to adorn your suit) make for great conversation starters. They can be helpful at an event where you weren't sure you would have other topics to discuss with confidence.
Men who make this small effort can see it return significantly in the appreciation for your flowers at an event and from the people who are willing to discuss the flowers and your suit as a result.