"Ireland's Trees (Myths, Legends and Folklore)" excerpt from Niall Mac Coitir

But there is a dimension to trees other than their numerous practical uses. There is something about trees that gives them a symbolic importance.

The lifecycle of a tree from seed to sapling to maturity, to withered old age and death, mirrors that of man. Trees, like people, bleed when cut, even if it is sap that flows out instead of blood. The tree is a powerful symbol of our own life in its various forms. Psychologically it is recognized that trees represent 'the living structure of our inner self'.  According to psychological theory, in dreams the roots represent our connection with the physical body, the trunk the way we direct our energies through growth, sex, thought and emotion. The branches represent the abilities and directions we develop in life and the growing tips show our aspirations and personal growth. Taken together these different dimensions to trees have led to them being seen since ancient times as powerful symbols of fertility, and the living abode of gods. The result is that a rich complex of myth, legend and folklore has built up around trees which is still with us today.

This dual aspect, both practical and symbolic, to the significance of trees brings us to one of the most basic mistakes made about tree folklore. Many scholars are uncomfortable with the idea of trees being regarded as sacred, and so try to find a practical explanation to refute such a notion. This approach is incorrect, since presenting practical reasons to oppose the sacred is a false dichotomy. Taking an example unrelated to trees, the Plain Indians of North America regard the buffalo as sacred, since it provides them with food from its meat, clothing and shelter from its hide, and various implements from its bones. It is seen as a gift from the Creator, imbued with supernatural powers, sacred because of its many important practical uses, not despite them. In the same way the oak was regarded as particularly favoured by the gods due to its many valuable attributes. The distinction between the sacred and the practical, therefore, is a very modern approach and it is inappropriate to project the distinction onto people who would not have understood it.