Now some would say that anything works but here where many of my weddings are on the beach I would recommend that you choose a flower that can handle being without water for a while and one that is a little sturdy as sometimes beach weddings involve more movement than a church wedding.
Such as venturing over rocks or dipping your feet in the ocean and so Gerber’s, Calla’s, Orchid’s and Roses are fine as long as they have a few stems of greenery to support them but on their own a bit fragile.
I also find Roses are a bit too heavy for Boutinnieres and tend to fall over or droop.