In Germany and Austria the maypole (or Maibaum) is a tradition going back to the 16th century. It is a decorated tree or tree trunk that is usually erected either on 1 May – in Baden and Swabia – or on the evening before, for example, in East Frisia. In most areas, especially in Baden-Württemberg, Bavaria and Austria, it is usual to have a ceremony to erect the maypole on the village green. The custom of combining it with a village or town fete, that usually takes place on 30 April, 1 May or at Pentecost (Whitsun), is widespread. This tradition is especially strong in the villages of the Bavarian Alps where the raising of the traditional maypole on 1 May in the village square is a cause for much celebration. The pole is usually painted in the Bavarian colours of white and blue and decorated with emblems depicting local crafts and industry.
Just before the Maibaum is erected, depending on the region, there may be a procession through the village, usually ending up at a central place and/or restaurant and usually watched by crowds of spectators and accompanied by a brass band. The actual installation of the tree then takes place in the afternoon or evening. While the crowds usually while away the time drinking beer and eating sausages, the young men busy themselves with decorating the maypole to get the symbols of various trades representing the region into the right position. While the maypole is traditionally set up with the help of long poles, today it may sometime also be done using tractors, forklifts or even cranes. In Lower Austria ropes and ladders are used.
If the tree is erected on the eve of 1 May, then the event is usually followed by a May dance or Tanz in den Mai.
Depending on local custom, the Maibaum may remain in place until the end of the month and is then taken down, decorations removed and the trunk stored until the following year. In many parts of Bavaria it remains in place all year round.
On the night of the last day of April, many young men erect small decorated "Maibäume" in front of the houses of their sweethearts. Some attach a red heart with the name of the girl written on it to the tree. (explanation courtesy of Wikepedia)