Trees were very sacred to the Druids, and Druids would often craft staves out of specific trees to hope to gain the proerpties that said tree was beleived to possess. Though Oak was one of the most common and highly regaurded of trees and woods. Ther were others which were imporant. Here is a list of different trees and what the qualities of each are:
Aspen: Invokes understanding of the grand design
Birch: Signifies new beginings
Holly: Inspires visions and reveals past lives
Oak: Brings healing, strength and wisdom
Pine: Signifies prospertiy and growth
Willow: Invokes the Goddess to achieve desires