I did a little research (Wikipedia haha) and found this information: Many of the oldest evidence in Sweden regarding maypoles, occur in different forms of prohibition, but most are not aimed at the erecting of the pole itself, but rather towards the festivities around it. The oldest known depiction of maypoles in Sweden occurs in Erik Dahlbergh's great 1500th-century painting Suecia antiqua et hodierna, where it appears that it was quite common in the cities of the same century. At this time, the poles were up all year long, a tradition still in place in some places in Dalarna. Different villages also competed among themselves as to who could erect the most beautiful pole. In the Middle Ages, wreaths were hanged around the pole instead of the cross shape that occurs today. This variant remains in Germany and also occurs locally in Sweden. There are different theories about the origin of the maypole. According to Mai Fossenius, the Swedish maypole has its background in German tradition, where it was decorated with leaves and foliage on festive occasions, which also became popular in Sweden in the 1200s. It is probably a Roman custom to decorate with green leaves in connection with the New Year that has been associated with the first of May celebration in Northern Europe since May 1 has been counted as New Year's Day. [8] A common, but wrong impression, is that the maypole would be a phallic symbol, but the notion that it in the past would have symbolized a phallus is lacking evidence. The idea of the maypole as an ancient phallus symbol emerged during the late 19th century, and according to ethnologist Jonas Engman, is connected with the influence of Freud and psychoanalysis. On the other hand, the pole might be inspired by Christian symbolism, Engman writes. Midsummer night has been attributed to magic powers. According to one tradition, the wreaths were saved to put in the Christmas bath, which would be a way to stay healthy and strong during the winter.

Hi I don't know about Sweden but in England dancing round the Maypole is an ancient fertility rite. The maypole is a phallic symbol. People still dance around the maypole today but only for fun :)