18 Feb Bottlebrush or paperbark? Callistemon or Melaleuca?
• Guest post by Malcolm Tattersall •
This all began with a somewhat puzzling comment in the gardening column of our local newspaper, “The Tinaroo Bottlebrush (Melaleuca recurva but still sold as Callistemon recurvis) is…”
“Isn’t a Melaleuca a paperbark?” I wondered. A bit of digging (no, not in the garden) showed me that what I thought I knew wasn’t true any more.
We have two kinds of names for plants, common names and scientific (Latin) names, and in this case both are problematic.
Scientific names are more precise than common names but they are sometimes changed by the taxonomists, and any changes take time to percolate through to the rest of the scientific community and the general public. In this case we had two closely related groups of plants long classified in two genera, Callistemon and Melaleuca, recently merged under a single name. Callistemon [species name] therefore became Melaleuca [species name] overnight.
The rationale for the merger is explained in this excellent article on the Australian Native Plants Society (Australia) website:
…the problem with the current classification on the basis of the arrangement of the stamens is that this supposed difference is not clear cut and Callistemon tends to merge into Melaleuca rather than being unambiguously distinct. The well known Callistemon viminalis is one that has often been discussed as not easily fitting the accepted definition of Callistemon.
…A paper by Lyn Craven of the Australian National Herbarium (Novon 16 468-475; December 2006 “New Combinations in Melaleuca for Australian Species of Callistemon (Myrtaceae)”) argues that the differences between the two genera are insufficient to warrant them being retained separately and that they should be combined. As Melaleuca has precedence, adoption of Craven’s work would transfer all species of Callistemon into Melaleuca. Some state herbaria have adopted this change but, at this stage , the re-classification has not been taken up in the Australian Plant Census, which ANPSA recognises as the authority on plant nomenclature.
While all Callistemons have their flowers arranged in a “bottlebrush” shape the inflorescences of Melaleuca may also have a globular or irregular shape. It should also be remembered that there are other genera in the myrtle family which may have free or united stamens combined with “bottlebrush” flowers. Botany was never meant to be easy!
So the debate began more than ten years ago and the result is still not universally accepted. The Bush Garden Nursery, however, has made the change: you won’t find a Callistemon on the stocklist. One last little wrinkle is that the form of the species name must match that of the genus, which is why Callistemon recurvis became Melaleuca recurva rather than M. recurvis.
Paperbarks are named for their bark and bottlebrushes for their flowers. Given that some bottlebrushes have papery bark and some paperbarks have bottlebrushy flowers (sorry, but it’s hard to be more serious), the separation of their common names must always have been blurred. In fact, one particular tree in our own garden worried me for years on just this account. We have two small trees which are unambiguously bottlebrushes, one huge tree which is unambiguously a paperbark, and a tall but very scrawny tree with loose flaky bark and the red bottlebrushy flowers pictured above.
Should we call it a paperbark or a bottlebrush? We can call it whichever we like, since common names are like that. Is it a Melaleuca or Callistemon? Well, it’s now a Melaleuca, whatever it used to be.
My Friendly Local Expert put my mind at rest when I asked, informing me that it’s the rare red-flowering form of the common Melaleuca viridiflora, so it has always been a paperbark and a Melaleuca. I should have asked long ago!
Just for the sake of completeness
- Banksias also have bottlebrush-shaped flower spikes but are distinctive enough not to be easily confused with Melaleucas.
- Grevilleas are more closely related to Banksias than to Melaleucas but some have flowers which might mislead the casual onlooker. The common name of large species is “Silky Oak” but most species are known by the Latin name.
- In some ways Hakeas forms a link between Grevilleas and Banksias, having hard woody seed pods with Banksia-like seeds while the flowers occur in Grevillea-like clusters.
- Leptospermums are in the same family as Melaleucas (Myrtaceae) and share their common name, “Tea Tree” (also spelt “ti-tree”), with paperbarks.
This article first appeared on Green Path, Malcolm’s wildlife and environment blog, in 2018.