Crystal Trees could be found in the Mortyablo Deja Moo Event and Merge Dragons! Birthday Event throughout the island, with Plum Willow being the highest leveled Tree. Through merging, a Crimson Elm could be achieved. The whole Merge Chain had been unlocked from the beginning.
They could be harvested for Crystal Fruit of various levels which were used to gain points for rewards in the Event. From level 3 onwards Crystal Trees could be tapped once a while for Crystal Fruit corresponding to their description. Rarely could be harvested for Crystal Chests.