I'm not an artist, but a "serious" battlemap user, so my opinion is: your map is totally OK. You and your players can easily follow the terrain types which is important, and if the PCs or some enemy like to climb trees, then it is the best method to put down full trees. But I think most of the time the fight goes under the trees an around the tree trunks, so I prefer when you can see the trunk (it's not so beautiful, but useful).
What will happen there?