Ah, the wall tree! What a wonderful idea for adding some Christmas spirit to your home! It's easy and can be done with just a few supplies. First, you'll need a flat wall that you can hang your tree on. You can use an existing wall in your home, or even create a temporary wall by attaching a piece of plywood or drywall to a freestanding frame. Next, you'll need some branches or twigs to form the shape of the tree. You can use real branches, or even artificial ones if you prefer. Once you have the shape of the tree, you can decorate it with lights,