A number of the commentators on the site mentioned that the brooch did not look like hibiscus flowers.
I wondered if that is because people were thinking of the popular cultivars of Hibiscus frequently seen in tropical gardens and commonly referred to as Hawaiian Hibiscus?
In an article published by The Court Jeweller in July 2018 to which the site directs readers the site owner, Ella Kay, noted that, "the hibiscus is an important flower in Australia -- so important, in fact, that the nation even has an Australian Hibiscus Society."
Perhaps, given these perspectives on the Queen Mother's Hibiscus brooch, some clarification is warranted.
First, there are many Australian plant societies which focus on various species. The Australian Hibiscus Society is a Queensland based society, perhaps primarily because hibiscus is a popular garden plant here. See https://www.australianhibiscus.com/
That there is an Australian Hibiscus Society is irrelevant to the Queen Mother's Hibiscus brooch as it is not based the type of hibiscus commonly cultivated in tropical and semi tropical gardens.
The design of the flower in HM's brooch is based on a species of hibiscus endemic to the warmer parts of the east coast of Australia. It used to be referred to as the Queensland Native Hibiscus.
Queensland native hibiscus flower (it also comes in other colours)
The distribution of this species.
For other information see https://www.anbg.gov.au/gnp/interns-2002/hibiscus-heterophyllus.html and for other species of hibiscus endemic to Australia see CSIRO's blog https://blog.csiro.au/uncovering-australias-little-known-hibiscus-species/
One of the commentators on The Court Jeweller site thought that the larger, open bloom in the brooch resembled a poppy, as indeed it does, unless we are aware of what the Queensland hibiscus looks like.
QEQM's Hibiscus brooch
Queensland native hibiscus
The Hibiscus brooch, like the Wattle brooch, was based on an endemic Australian plant.
In The Court Jeweller site, Ella Kay states that the Hibiscus brooch was designed and created by a Mr WJ Laver of a Collins Street jewellery store, and references an unidentified issue of the Sydney Morning Herald.
As the Sydney Morning Herald for 1958 has not been digitised and made available on Trove, I cannot comment on that newspaper's sources etc; however, it was well publicised in the contemporary Australian Press that the maker was an independent manufacturing jeweller, Joseph Mann of Melbourne, an immigrant who was born in Hungary, trained in Vienna and then worked in France for many years before arriving in Melbourne immediately after WWII. As I have published extensively on this years ago, I won't repeat all the information again. He also made the Wattle brooch presented to QEII by the Australian government.
Joseph Mann holding the Queensland Hibiscus brooch.
Joseph Mann at his work bench
The designer of the brooch was Ross Allan. He had worked in one sector of the jewellery manufacturing trade and then worked for two leading Melbourne retail jewellers, continuing his extraordinary design career.
His designs for the Queensland Hibiscus brooch are now held by the National Gallery of Australia.
As can be seen on this first sketch, Ross Allan clearly marked the sketch as being of a Queensland native hibiscus and originally designed the brooch to have opals.
When Clarence House rejected opals, Ross Allan adapted his design to have rubies, as can also be seen in another of his design sketches held by the NGA.
It was no secret in Australia that the Queen Mother rejected opals, and there are several press stories about this all at the time the brooch was presented.
For me, one of the most interesting things about the design and manufacture of this brooch is how closely Joseph Mann was able to follow Ross Allan's design. Below is a comparison photo where the actual brooch is on the left and one of Allan's design drawings is on the right. Because Allan worked within the trade he knew how various techniques worked, and Joseph Mann had the skill to realise the design.
The Hibiscus brooch became one of QEQM's favourites. She wore it a number of times during her 1958 Australian tour.
Below are 2 photos of her at the University of Queensland in 1958.
Queen Elizabeth II has also worn the brooch a number of times.