You can see it here.
Thanks for chiming in all. I do hope for a solution, as it's hardly viable to have to subdivide all trees (and other stuff) to be 100% smooth. Not easy too, as it's only the lower trunks that really need it, it needs a hand, not just a total subdivision (as usually, in my case, trunks and branches use the same texture). But I really though this was subdivided enough, seeing the wireframe.
Btw. it's not duplicated meshes or something like that, it's very clean.