I really love those trees. At first I thought they where to big for little Morrowind but now I think they are fine(especially after seeing the ashland trees:D)
However at night the leaves somewhat bug me. They are too shiny.
http://img188.imageshack.us/img188/8817/morrowind20100119234556.jpg
http://img511.imageshack.us/img511/5242/morrowind20100119234532.jpg
The dark green leaves fit in however.
It will look different depending on angle / direction of light.. If you had went to the other side of the tree it would have looked like this: http://piclair.com/data/gbb39.jpg as you can see they're not very bright at all from that side because the light comes from another direction.
I dont think im going to make them any darker. Stars/moon would IRL make the tops of trees at least a bit bright from the light, so i dont think it looks that unnatural + the leaves would be way too dark in day light.
Are you also planning to do (animated)mushroom-trees?
I could try and see how it looks i guess, but i'm not too keen on spreading meshes that arent my own though :/ and i dont think im going to make my own mushrooms, i think the Bethesda ones are quite ok looking.