In this quick tutorial, I’ll walk you through the process of setting up the FiberMesh settings to produce the trunk, the branches and the leaves for a low-poly tree in ZBrush. The technique in this tutorial can be applied to a variety of things by simply tweaking the settings on each step.
“Fractal” approach to building things…
The technique of this tutorial is rather simple once you know the steps. Once you have a good grasp of how the settings in FiberMesh affect the shape of the objects, you can create a wide range of things following the same process.

You can generate fairly convincing trees in a few minutes. Playing around with the settings of FiberMesh, you can also create very abstract objects that follow a similar pattern:

Treen and forest ZTool
In the resources for this tutorial you can download the ZBrush ZTool that contains multiple subtools with the trees and the forest examples. Also make sure you check the FiberMesh settings section on the resources page where you can grab the 4 settings I showed in the tutorial.
Check it out