I re-optimised and re-unwrapped the great tree.
[edit: dropped saturation and changed hue of leaves]
[edit: fixed seams, added moss (though from so far away, its hard to notice, adjusted colors, re-oriented bark-flow]
[edit: dropped a few polys]
The tree is very large, so I will probably not optimize its topology too much farther, as i want to have a smooth read, even if the player stands on the roots.
I will also be adding moss and roots to the base.