If you change the branching probability all the way to the right, the vine does't branch much.. great for having creeping ivy on a floor.

I haven't played with all the settings, but here's another little thing I discovered: you can make a setting, then have the ivy grow. Then you can stop the growing, alter settings again, and continue growing.

So, changing branching probability to 1, click grow, it'll grow with one vine. Then after a bit I stop it, change the branching probability to .955 and it starts to branch. Changing the other settings and it starts looking very interesting.