Buttenhole or flower in the left lapel of the groom is always in the same color and style like the wedding bouquet. If wedding bouquet is from one kind of flowers, one flower is used for buttenhole. And if it is a wedding bouquet composed of more kinds of flowers, it shall apply one of these species, usually the dominant color or the predominant and matching with the suit for the groom.
Buttenhole is mounted on a special pin.