They can be found in any location with the exception of the dungeons. Tree types vary throughout the different teleports. Some are as tall as Sherwood Castle while others may only be as tall as a Dragon.
Most notably, a decorated Yule tree will replace the Dragon Statue in Sherwood Castle during the holiday season. The tree is decorated with different gems/ornaments that appear to follow the colors of the six elements in Sherwood Dungeon. The tree replaces the Dragon Statue from the beginning of December to mid January