Aha, I went home to try to reproduce the problem on another PC and was able to do so. So started digging around and indeed found that there is a "Cycles Hair Settings" and the root was a lot bigger than than the tip. Nice find, Jonathan and me! I had no idea such a setting existed since I am a Blender Render kind of guy until PC's get 10000 times faster :).
I did learn that its quite easy to make a low poly forest with these settings :).
