Draw big "v's" onto the sides of a plastic milk bottle. When cut with a craft knife, these become your branches.
Paint and decorate your tree however you want.
Plastic drink bottles, cut in half and fringed from bottom to neck make great little trees when stacked onto a used CD stacker.
Reduce, reuse and recycle this Christmas. Make what you can out of trash and give landfill a welcome Christmas present of respite.