Collect leaves from around your home or from a nearby forest. Select about five to 10 large, whole, interesting-looking leaves, depending on how many different shapes you want to use for your tree costume.
Trace the outline of each leaf on scrap paper, and cut out the outlines to use as a template for your fabric. Do not discard your leaves.
Place your leaf templates on your fabric, and trace around the templates with chalk. Make as many leaves as you'd like for your tree. Forty to 50 large leaves or more will create a fuller looking, more realistic tree. Make double that amount if you're working with single-sided fabric. Use several fabric textures and colors for more attractive results.
Heat up your hot glue gun, and glue matching leaf sides together; this step is only necessary if you made twice as many leaves because of single-sided fabric. Glue the uncolored sides of the fabric together when you glue your leaf sides together.
Sponge a thin layer of fabric paint over the face of a leaf. Find its matching fabric leaf, and gently press the real leaf's painted side over the fabric leaf's fronts. Allow the paint to dry, and then paint the back. This process creates a faint imprint of a real leaf's face onto your plain fabric leaves.
Repeat the process with all the leaf shapes. Once the painting process is complete, you can discard your real leaves.
Attach your leaves to your tree costume with hot glue by the stems. Cover any obviously glued areas with glued-on fake moss.