I did not find a question on these lines yet, correct me if I'm wrong.
Trees (and fauna in general) are common in games. Due to their nature, they are a good candidate for procedural generation.
One could use either of above (or some other tree generator I haven't stumbled upon) to create a few dozen tree meshes beforehand - or model them from scratch in a 3d modeller - and then randomly mirror/scale them for a few more variants..
But I'd rather have a free, linkable tree mesh generator.
- Port proctree.js to c++ and deal with the open source license (doesn't seem to be gpl, so could be doable; the author may also be willing to co-operate to make the license even more free).
- Roll my own based on L-systems.
- Don't bother, just use offline generated trees.
- Use some other method I haven't found yet.
Update 2015: ended up porting proctree.js to c++ https://github.com/jarikomppa/proctree