Smoke
Ignore-Amus
Balance, as I understand it, is that:
1. The tree does not appear as though it is going to fall over. It has the appearance of a strong base which will hold it firmly to the ground.
2. If you were to divide an image of a tree into 4 quadrants, each would be balanced by the quadrant next to or adjacent from it. For example, the tree in this thread, image one, has balance. The foliage is counter balanced by the negative space adjacent to it.
This is not to say that symmetry is necessary for me in art, but that I prefer an image with balance.
So your definition is personal rather than universal?