May Day originated from the combination of the Druid festival Beltane and the Roman festival Floralia that was introduced to the British Isles. Beltane involved moving cattle through a fire before extending their graze land for the upcoming summer. For Florales Ludi, Romans celebrated Flora, the goddess of flowers, representing the coming of spring. Although May Day is not an official holiday in the United States, some American families with British ties and families in Europe continue to celebrate it.
The blossoming of flowers is an important symbol of May Day festivities. Homes and the maypole were decorated with flowers, and baskets of blooms were given as gifts. Select a costume with a floral theme. Cover an old dress with real or plastic flowers, and create a crown out of foliage and blossoms. You could even dress up as the goddess Flora. Wear a white, draping robe, and create a flower crown and garland for accessories.
During the medieval period, May Day celebrations were dynamic and consisted of the crowning of a May Day Queen and the performance of mummer plays. Mummer plays were musicals where characters performed ceremonial dances. Half of the characters represented evil and were led by the Winter Queen, who duelled against the May or Summer Queen and her "good" assembly. The May Queen and her troupe always won. You could dress in medieval period costume for May Day. Males could wear a tunic with tights, and females could wear a long, loose woollen dress fitted at the waist. You could also dress up as Robin Hood, Maid Marian or Friar Tuck, as they were popular characters in the mummer plays.
The Morris dance was a folk dance traditionally part of May Day celebrations. Participants would play instruments, beat on drums, dress in costumes and dance. Some of the costumes involved mythical animal themes, such as a half-man, half-horse outfit. You could wear such a costume or create your own half-human, half-animal disguise.
For a tongue-in-cheek costume idea, you could dress up as a maypole. Maypoles were typically decorated trees. Wear a green top, a brown bottom and foliage in your hair. Drape yourself in garlands of flowers, and attach streamers around your shoulders.