Bottlebrushes are members of the genus Callistemon and belong to the family Myrtaceae. They are closely related to paperbark melaleucas, which also have 'bottlebrush' shaped flower spikes. It is difficult to tell to which genus some species belong. Botanists are currently closely studying these plants to determine how they are best classified. There are 34 species currently called Callistemon .
Most Bottlebrushes occur in the east and south-east of Australia.
Two species occur in the south-west of Western Australia and four species in New Caledonia. Bottlebrushes can be found growing from Australia's tropical north to the temperate south. They often grow in damp or wet conditions such as along creek beds or in areas which are prone to floods. The flower spikes of bottlebrushes form in spring and summer and are made up of a number of individual flowers. The pollen of the flower forms on the tip of a long coloured stalk called a filament.