SpeedTree for Unity 5

With the full release of Unity 5, you can have AAA tree editing tools by subscribing to the SpeedTree Modeler, available for Windows and Mac OSX
You must have Unity 5 to use SpeedTree with the engine. Trees and plants created with the SpeedTree Modeler will work with Unity 5 Beta, but not Unity 4 or Unity 5 alpha.
Highlights of SpeedTree for Unity 5:
Scalable wind effects, including Wind Wizard
Seamless LOD tuning
Unlimited variations with one click
Branch seam blending
Sub-division surface modeling
Collision primitives added automatically or manually
Modeling with mesh forces (e.g. grow trees around or through 3D meshes)
Much more! See our online Modeler documentation for complete details.