Myrtaceae

Callistemon is a genus of exotic flowering plant from the Myrtle family, Myrtaceae. Commonly called the bottlebrush plant for obvious reasons. 

Currently, there is a debate as to what plants should be specified as Callistemon and those that are a closely related genus, Melaleuca. It appears that on DNA evidence alone most Callistemons are in fact Melaleucas. This is disputed due to differences in physical make-up of the flowers. This has been going on for over 150 years so still a work in progress.

What is the difference between Melaleuca and Callistemon?

The two genus both belong to the Myrtaceae family but historically have been kept separate because of certain characteristics of the flower. In both cases they can look like a ‘bottlebrush’, ie. A brush for cleaning bottles with. The stamens growing in clumps from the central woody branch with just a small petal array at the base of each clump. 

The melaleuca was defined by the difference that these multi-stamen flowers had stamen that are fused into small groups at the base, whilst Callistemon doesn’t. That isn’t a valid difference in every case. For instance Callistemon viminalis (Weeping Bottlebrush) has stamen that are also fused into small groups at the base. 

Recent use of DNA testing has shown that these two genera are more closely connected than was originally assumed. Most botanists will take one side or the other, follow the DNA or stick with the visible characteristics and keep the two genera separate. Where I live, if they look like a bottlebrush, they will be referred to as Bottlebrush for a long time to come.