I was informed May Day, with its requisite maypole, is a public event centered on a town or village "happening". The annual appearance of a maypole normally occurs either on the eve of the first day of May or the first day itself. As a centuries old tradition, this may include a village procession or parade with much music and spectating. I had missed the Graz parade and it was well after May Day; maypoles apparently stay in place for a month or longer. On this particular spring day, I did observe many eating sausage and drinking beer, though this may be mere coincidence. These are notable activities on just about any nice European day.
In other towns and villages, I've noticed erected maypoles adorned with empty bottles -- no doubt garnishment borne of a working gang's thirst, accoutrements required to select, deliver and stand a carefully prepared tree. I can only speculate the bottles once held pomp and circumstance in the form of vodka, schnapps, borovica, or slivovica.
I'm not surprised theories abound around the symbolism of the maypole and its varied decorations, with much speculation tied to some long lost pagan tradition -- similar to those which align behind the Christmas tree. I certainly have produced my own plethora of hypothetical explanations. Oh, Tannenbaum.
I was also informed that during the night of the last day of April, many a young man ventures into the woods, selects an appropriate tree, strips it of most its branches (except for the top), decorates it with his identifying "colors" and then erects it in front of a potential girlfriend's abode. For established pairings, it is custom to find a flowering fruit tree, under which to exchange a symbolic kiss -- Nature's calling for all to join in regeneration. It is at this point some theorists invite Sigmund Freud on in for comment.
From my point of view, the variable with May Day and maypoles is the application of local custom. The constant seems to be man's need to be in a recurring mode of celebration -- this being just another one of many.