Sardi Pax Covers Making Trees Using the Blender Sapling Addon, Showing How its Possible to Create Realistic Animation.
Every DCC has a method for creating vegetation and trees, either through its toolset or by using a specialized plugin. There are even lots of third-party tools out there, some of them stand-alone, like SpeedTree. If you are working with Blender, that application also has its means, in the Sapling addon. Sapling Tree Generator comes with your installation of Blender and works by using a simple curve.
The Addon is simple to work with and garners excellent results. Watch Blender Artist Sardi Pax covers how to create trees using the add-on, and how to create a realistic animation with swaying limbs and flapping leaves. Pax covers most of the controls and explains how they work for creating reasonably practical trees with minimal effort.