We did Seussical a few years ago on a relatively small stage.  We had a series of levels created with bright colored platforms that fit together like puzzle pieces.  They could become jungle, whoville or whatever and gave us lots of levels on the stage.  The tree was built from wood covered with chicken wire and dutchmaned to become a tree.  The top had a platform with a ladder up the back so Horton could climb up.  We built a big nest at the top with branches made from dried christmas wreaths from a craft store.  It was amazing.  Also made a huge egg from paper machet and had a 2nd one we cut open and put in a remote control device so it would make the egg shake before it hatched.  Pillberry bush was made of sticks stuck into a bucket of sand with large colored jelly beans hotglued on.  It looked really great!