Dimension Tree is a type of tree. It is one of seven trees available after acquiring a Nursery when constructed.
It's appearance is 9 perfectly cube-shaped trees with one orange in the middle. It is said that the gardener forgot to water the middle tree for a very long time.
To obtain the Dimension tree it is available in the Land section under the Landscape button. Then simply click on the "Tree" sub-section and the full list of all seven trees will be at your usage. This tree is the second option.