This tree isn't actually native to South Africa so we shouldn't celebrate it but we do because we like it. There's a big drive in SA to remove all plants known as 'alien invaders' as they have a detrimental impact upon the indigenous vegetation and the water table. Thankfully however the Bottlebrush tree doesn't have a big thirst so there's no need to get rid of it.
Here's some info from a horticultural website: Bottlebrush is a small but spectacular evergreen tree or shrub. Of the family Myrtaceae it is well known as Callistemon or Bottlebrush Tree. It is easy to grow and loves warmth, moisture and sun. Bottlebrush is native to Australia mostly growing in moist soil in open or woodland sites.