The excitingly-named "tree" program was written in C++ and uses Trolltech's QT library. The basic framework for the program was borrowed from the "texture" program in the QT examples directory, but the drawing code is all original.
To compile the program, you need QT with OpenGL extensions compiled, and OpenGL. You can download the source here. And here are some screenshots:
The tree's died and is listing dangerously to one side:
You can also rotate the tree, zoom in and out, watch it grow and enable wind and fog: