From the great Wikipedia:
The symbolism of the maypole has been continuously debated by folklorists for centuries, although no set conclusion has ever been arrived at. Some scholars classify maypoles as symbols of the world axis (axis mundi)… One theory holds that they were a remnant of the Germanic reverence for sacred trees, as there is evidence for various sacred trees and wooden pillars that were venerated by the pagans across much of Germanic Europe, including Thor’s Oak and the Irminsul. It is also known that, in Norse paganism, cosmological views held that the universe was a world tree, known asYggdrasil…
…Non-Germanic people have viewed them as having phallic symbolism, an idea which was purported by Thomas Hobbes, who erroneously believed that the poles dated back to the Roman worship of the god Priapus. This notion has been supported by various figures since, including the psychoanalyst Sigmund Freud…
…The anthropologist Mircea Eliade theorizes that the maypoles were simply a part of the general rejoicing at the return of summer, and the growth of new vegetation.
Whatever you believe, we’re wishing you a wondrous first day of May.