- Create a tree in Unity 2018.3 and export it using the [Unity FBX Exporter][1]

 - Try the [Modular Tree][2] addon for Blender and then export as FBX
 - Trees are also created via nodes
 - Leaf placement was problematic and I encountered a few minor bugs back when I used it
 - The new Blender version 2.80 might not yet be stable but 2.79 should be fine
 - It's free & open source


 [1]: https://assetstore.unity.com/packages/essentials/fbx-exporter-101408
 [2]: https://github.com/MaximeHerpin/modular_tree