Celtic tree zodiac- Oak (June 10 - July 7) Represented by the Oak tree, you stand out for your reliability, diligence and emotional strength. Your ogham is Duir, which holds the powers of protection, ideal when you're about to undertake a difficult project. The wren, the otter, and the white horse are the animals the Celts associated with the Oak tree sign. Your color is black and your gemstone is the diamond.