Tall centerpieces need big flowers to fill in the empty spaces. If you don't care for hydrangeas, you can replace the same spaces with other large flowers, such as sunflowers, allium or oriental lilies. You can also mass smaller flower heads together for more effect.
Begin inserting your white hydrangeas in between the spaces of the bright pink hydrangeas.
Don't feel compelled to make this centerpiece as shown. All these flowers come in many different color choices or you can simply substitute other flower varieties.
For the top center hydrangea, place the white one next to it, angled outward and a littler lower.
Don't forget to take a step back occasionally, viewing the design from all sides.
Once all the hydrangeas are in place, we will move on to the secondary flowers. In this design, that will be pink roses.