It is the flower of Eucalyptus cladocalyx nana commonly known as Gum Tree or Dwarf Sugar Gum.

Small to medium sized tree 4-6mx 3-4m. Dense rounded canopy of foliage. Rounded juvenile foliage and elongated mature foliage. Creamy white flowers in spring and summer. Full sun/part shade, most well drained soils, tolerates poor infertile soils and dry conditions. Ideal for use as a screen or windbreak. Good firewood tree.

Nice contest by the way. Thanks.