A boutonniere is a single flower or small floral arrangement used to adorn the lapel of a suit coat. Traditionally a boutonniere is meant to be worn through the left lapel buttonhole; though since tuxedo jackets today oftentimes are constructed without buttonholes, boutonnieres are oftentimes attached with small pins instead. The boutonniere is usually worn with a tux and bow ties, or tux, waistcoat, and neckties.
The traditional flower for use in a boutonniere is a single red rose or white carnation oftentimes offset with a small amount of white babies breath. Though these are the most traditional colors and flowers to use a boutonniere they are by no means a rule, and in fact it is now more common for boutonniere is to be constructed out of flowers that match the outfit which it is accessorizing. In the past boutonnieres were worn quite commonly at social events and even for formal day wear. However, as social dress codes have relaxed significantly in recent times it is now only common to see boutonniere's worn at special occasions such as weddings, proms or other formal gathering where a tuxedo would be appropriate.
Boutonnieres are not to be confused with a corsage which is the female equivalent and can be worn on either the woman’s dress or wrist.