Really good work on the leaves, but I'd agree with the others as far as the top of the tree and the roots go.
Yeah, the tops look very flat, and the red things are not very readable.
Those are the only issues I see, the sides of the trees and the colors are great :)
Those are the stumps at the bottom of the tree. The bigger one is a bit flat at the top, I've played around with repeating layers of the same colors but I dont like the look much. To add more layers I'd need more colors, which i'd rather not do.
You might want to try a better perspective with more layers of leaves, the big one looks really flat on top.
Also, what's on the bottom? Mushrooms? Roses?
Gotta love minish cap! Nice job on these.