Well, that's certainly an interesting question! Let's see......first, you'll need a bunch of balloons in various sizes and colors. Then, you'll want to start by blowing up a few of the balloons and tying them together at the base to form a small cluster. Next, add more balloons, layering them in a way that creates the shape of a tree. Finally, top it off with a star or other festive decoration. There you have it, a balloon Christmas tree!