Although having nothing to do with me, I found this nice treelike structure that exhibits the Fibonacci number properties (the increasing branches) which is not very hard to achieve with an L-System. At its most basic form it would look like this.
A → AB
B → A
I’m fairly happy with the script as it gets the job done and it is available for download here. There are a lot of tweaks to be made, for sure, but these curves are all produced in Illustrator. This is one of my favourite grammars, the Cesaro’s Sweep. It is actually a variant of the Koch Snowflake but I think it looks like trees. Another one of many variants of the Koch curve. This is a Quadratic Koch Island. The last one is called a dragon curve. The keen observer will also recognize this as the curve from the Jurassic Park book. There is also a pretty handy Java applet by Christopher G. Jennings to play with here.