The trunk consists of solid rocket fuel. Its leaves are described as having a yellow color and looking like a cross between moss and wool. Its bark is gray and it produces flowers. The original stage trees grown during the times of the Slaver Empire were described as looking slightly different with dark blue bark and a giant green flower on top mimicking the Mpul trees from which they were created.
Grown in plantations during the time of the Empire. The solid-fuel rocket cores inside their bark were used by the Slavers to lift their ships in places where a fusion drive would have done damage. Slavers stopped using them a few decades before the demise of the Empire. 
The stage tree has two lifecycles, the bush form and the multistage form. In the bush form the stage trees reach heights of four to six feet and are described as slender and straight with brilliant yellow foliage at the top flattened like a dandelion's head. If a seed finds particularly fertile ground the bush enters the multistage form. In the multistage form the living parts of the tree consist of the tap root and the yellow foliage around the base. The center of the tree is devoted to creating a gray dead-looking spire of solid rocket fuel reaching heights of up to half a mile with a seed pod at the top. When the tree reaches maturity as indicated by the graying of its foliage the spire ignites and takes off like a rocket leaving the solar system is in. It floats in interstellar space for hundreds of thousands of years until finding a new system where the seed pod explodes, if a habitable planet is in orbit and a seed lands on it the cycle starts again.