21 in Potted Double Ball Topiary Tree Form measures one 3" and one 5" diameter foam ball with 5" diameter pot base, thick twig trunk, 21" tall. Make floral centerpieces easily. To hold topiary form in container place a piece floral clay on the bottom of the container. To help it fit more firmly wedge a few pieces of styrofoam or floral foam between form and pot. Cover the top of pot with green moss and you are ready to start designing.