You could also use newspaper or scrapbook paper...heck even construction paper (maybe even tissue paper)!
Instructions
1) Spend some downtime punching out paper flower shapes. This is easy to do while watching TV.
2) Fold flowers over sharp point (do not crease) 3 times
4) Push flower tip into styrofoam ball
5) repeat until ball is full and no styrofoam shows through
Tips: Lightly spray edges of "petals" with any color of spray paint for a unique look. Pull string or twine through the ball to hang them or place sticks from the yard in them at different heights for a rustic center piece. Try mixing and matching hydrangeas made from different types of paper!