https://creative.pluralsight.com/tutorial/2120-Modeling-Realistic-Trees-with-SpeedTree 

In this SpeedTree tutorial we'll learn to model a realistic 3D tree from the ground up. Realistic foliage is an essential component for the creation of a believable outdoor environment. SpreedTree is a powerful tool that specializes in perfecting your foliage and trees to bring them closer to that realistic look you desire.

By the end of this SpeedTree tutorial, you'll have a good understanding of the program’s parametric tree creation toolset, which will enable you to create natural looking trees of all shapes and sizes.

Lessons in this tutorial

1. Introduction and project overview
2. Building a basic tree from scratch
3. Adding texture
4. Refining the trunk
5. Adjusting the branches
6. Refining the secondary branches
7. Generating leaves
8. Reshaping branches
9. Re-routing the roots
10.Cleaning up the tree with Node Editing
11.Creating low res trees
12.Making random variations
13.Exporting