Oak - The Stabilizer June 10 - July 7 Those born under the Celtic tree astrology sign of the Oak have a special gift of strength. They are protective people and often become a champion for those who do not have a voice. In other words, the Oak is the crusader and the spokesperson for the underdog. Nurturing, generous and helpful, you are a gentle giant among the Celtic zodiac signs. You exude an easy confidence and naturally assume everything will work out to a positive outcome.