Boutonniere:

This is what the gentlemen wears, it is worn on the left
side of the lapel on the jacket. When pinning on the boutonniere
if you place the pin closes to the top of stem, just under the head
of the flower it will stay nicely in place. If the pin is not in the
right place the flower will flop around. Your florist will always

be happy to show you where and how to pin it.
It should be simple with no more than one or two flowers.
Flowers that are normally used are roses, calla lilies , orchids.
The boutonnieres, does not have ribbon on it, but can be
decorated with a few pearls or gems to match his date.
You would also want the tie to match as well.
Here are just a few samples of what the young man are wearing
this graduation.