Spirit Trees are a very unique type of tree that will be found rarely in the Betweenlands when implemented. They will also be able to be grown with Spirit Tree Saplings.
The leaves are drooped on the logs and act as vines. The tree is unique in that it is a living creature of its own. The Spirit Tree Face will normally be sleeping, but coming within ten blocks of it will awaken it. Once you get within five blocks of it, it will become enraged and begin spitting blue projectiles to attack you. Fortunately, if you can get close enough to the face and break it you can stop these attacks. Then you can collect the wood and saplings from the tree, as well as Spirit Fruit from the leaves.