Callistemon serpentinus is an upright shrub that may reach a height of 4 metres. The bark is papery and flaking.
Callistemon serpentinus is a rare bottlebrush that is found just east of the Barraba district of northern New South Wales. There is a population around the Wood’s Reef asbestos mine near Barraba. This Editor does not know why the species is not listed as threatened.
Callistemon spp. have simple and alternate to spiral leaves. In this species, the leaves are to 60 mm long by 5 mm wide and have an acute apex.
In Callistemon species, flowers are usually arranged in spikes (the “bottlebrush”) which are produced at the terminals but which the stem then grows past, into a leafy shoot. Flowers have five small circular sepals and five circular petals which persist on the flowers. Like many other Myrtaceae genera, the flowers are conspicuously staminate with each flower having many stamens surrounding one carpel. The stamens are typically free although may be fused at the basal parts (a generally useful identifying feature for the genus to distinguish it from Melaleuca). The pedicels of the flowers are very short. In this species, the yellow flower spikes are about six centimetres long and appear in late spring and early summer. Flower spikes are both prominent and conspicuous. Their colour is not common in the palette of bottlebrush flower colours.
Capsules are to 4.5 mm in diameter, arranged in the same spike-like structure along branches.
Currently, not a lot is known about this species in cultivation. However, the author of this profile has grown it successfully.
Author’s note: Callistemon serpentinus could be grown in hedges and screens together with other varieties. Our specimens are kept to a dense height of two metres by annual pruning.
It can likely be grown on a range of soils with adequate drainage. It may be hard to source commercially.
Propagate from seed and cuttings. There is some evidence that Callistemons may hybridise. If grown with other varieties then propagation should be from cuttings. Cuttings will ensure that this attractive species comes true to type.
The genus Callistemon has been subject to recent taxonomic revision with early and recent botanists including Ferdinand von Mueller and Lyndley Craven (deceased in 2014) proposing to ‘lump’ the genus into Melaleuca and others. Craven et al. (2014) published new species combinations which included the renaming of all Callistemon species to Melaleuca, based on evolutionary relationships and DNA evidence and other features.
Currently, the NSW Herbarium advises that the Callistemon genus can still be used. There are currently about 30 species of Callistemon, which are found in all states of Australia as well as New Caledonia. About 28 are endemic to Australia. NSW currently recognises 24 species. New species have been described in the last 20 years.
Regenerates after fire from epicormic and basal shoots as well as from the seedbank.
Callistemon – From the Ancient Greek – Callos (κάλλος) – meaning “beautiful” (which is changed to κάλλη to describe a noun) and and stêma (στῆμα) meaning “stamen”, referring to the very showy staminate flowers of the bottle-brush inflorescences.
serpentinus – Latin – named for the serpentinite substrate on which this species if found; an silicate-based igneous rock containing high amounts of iron and magnesium.
This species is rare and restricted in the wild but not currently listed as being threatened with extinction.
NSW Flora Online (PlantNET) – Callistemon serpentinus profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Callistemon~serpentinus
Wikipedia profile page – Melaleuca serpentina profile page https://en.wikipedia.org/wiki/Melaleuca_serpentina
The Armidale Express – Armidale Gardening – Bottlebrush Time – by Warren Sheather https://www.armidaleexpress.com.au/story/4551318/bewildering-array-of-bottlebrushes/