London — Breathing hard, the Royal Ballet dancers lined up onstage here to take their bows after the premiere of David Dawson’s new piece last season. Out came the ushers bearing armfuls of flowers from the company. Then, to the shock of insiders and disapproval of traditionalists, bouquets were handed to the men as well as the women. Long-suffering balletomanes reeled back in their seats. Twitter was abuzz.

At the Royal Ballet, the great home of the floral tradition in dance, men don’t get flowers onstage. (Unless they are in drag. Which happens fairly often.) It’s one of the many customs, rules and subtle ordinances that govern the art of the bouquet in London. Flowers matter: how many, what kind, who they are given by, who they are given to, how they are bestowed, how they are received. (To present those opening-night bouquets to the men, Mr. Dawson had to get a special dispensation from Kevin O’Hare, the Royal Ballet’s director.)

Flowers matter in New York, too, where splendid bouquets will be handed out during “Nutcracker” season. (New York City Ballet’s version opens Nov. 28 at the David H. Koch Theater, and American Ballet Theater’s production arrives at the Brooklyn Academy of Music on Dec. 12.) But what can seem a simple gesture of appreciation is in fact a highly codified practice, with different ballet companies obeying different rules and traditions.

At City Ballet and Ballet Theater performances, flowers are generally given by the company on opening nights and for role debuts. At the Royal Opera House, however, there are flowers delivered onstage at almost every ballet performance, most provided by loyal fans who can spend hundreds of dollars each month to keep their favorite ballerinas supplied with floral tributes.