Trees should take time to grow. Longer than they already do. They should also get bigger. The current trees barely exceed twice a characters height. Some trees in real life can go far larger. It would be neat also, if trees were a little more varied. For example, they stop growing at random places. Sprout new limbs etc.

My "Mages Guild" has a single tree in the it. I would love for this to be a centerpiece rather than something that is odd and out of place.

It would also make for an interesting way to lay siege to someones castle. Plant a tree and then grow it rapidly with spells before climbing it and leaping over the castles walls. It would also be neat if trees could be ignited with spells or branches blown off.

All this makes me want to go out and play Real Life for a while. Lol.