Trees were highly regarded by the ancient celts, each tree was believed to have it's own spirit. The Oak was considered the most important among the trees. During the time of the Druids the dead were often buried in the hollowed out trunk of an Oak tree. The Oak was also used for Solstice festivals and Wiccan tools such as wand. The Celtic tree calendar was used as a time keeping device, the Celts found names and associations between the moon and corresponding trees. The trees Druids selected for the Thirteen Moons are saids to be favoured by fairies and elves of the forest. Each tree chosen for the calendar contains magical healing properties used in medicines and spell work.