Apart from Christmas, midsummer is the most important holiday in the Swedish calendar. And for some, the very most important. The successful midsummer never-ending lunch party formula involves flowers in your hair, dancing around a pole, singing songs while drinking unsweetened, flavoured schnapps and downing a whole load of pickled herring, served with new potatoes, chives and sour cream.
And from Wikipedia
Raising and dancing around a maypole (majstång or midsommarstång) is an activity that attracts families and many others. Greenery placed over houses and barns were supposed to bring good fortune and health to people and livestock; this old tradition of decorating with greens continues, even though most don’t take it seriously. To decorate with greens was called att maja (to may) and may be the origin of the word majstång, maja coming originally from the month May. Other researchers say the term came from German merchants who raised the maypole in June because the Swedish climate made it impossible to find the necessary greens and flowers in May, and continued to call it a maypole. Today, however, it is most commonly called a “midsommarstång” (literally midsummer pole).
In earlier times, small spires wrapped in greens were erected; this probably predates the maypole tradition, which is believed by many to have come from the continent in the Middle Ages. Others argue that some form of Midsummer pole occurred in Sweden during the pre-Christian times, and was a phallic fertility symbol, meant to impregnate women.[