Yellow-flowered myrtle from the big island

In dense forest or shrubland on hillsides throughout the main island (Grande Terre) of New Caledonia you might find a  yellow-flowering shrub or small tree in the myrtle family. The flowers, as you can see, resemble many of the Australian Myrtaceae, such as lily pillies and eucalypts. 

They also have, as you can see in the outer layer (sepals) of these flower buds, the distinctive oil glands often found in members of this family.  

You can also see faint red streak on the buds. That colour appears again when the flowers open, as a thin red line where the stamens (the pollen-bearing parts) are attached. 

The angular stems also caught my eye, but I'm not sure how widespread they are in the genus, or family.

Metrosideros is a widespread genus in the Pacific, perhaps best known in Australia by the New Zealand Christmas Tree or Pōhutukawa, Metrosideros excelsa. That species has similar looking flowers, but red in colour. 

There are about 60 species of Metrosideros, about 20 of them native to New Caledonia and a goodly number in New Zealand (you may recall me posting on a carmine-flowered species, Metrosideros carminea, a year or so ago).

In 1985, Metrosideros laurifolia was moved to a new genus, Carpolepis, along with a couple of other Metrosideros species from New Caledonia. While the characters that distinguished the new genus - yellow flowers, a tendency to grow sympodially (from lateral rather than terminal buds) and winged seeds - are distinctive, they are not unique among Metrosideros and all three species nestle within the evolutionary tree that genus. Which all means recognising Carpolepis as distinct requires the splitting up the rest of Metrosideros. Which we don't want. 

So in 2015, the two genera were recombined. At the same time, a new variety of the species called demonstrans was described based on another species of Metrosideros with that name. That variety is no longer accepted and considered to be part of a broader Metrosideros laurifolia. Another older variety minor also has no currency.

When I took these photographs in late March there were only a few flowers still open, and most had lost their yellow frills as they transform into fruits. The plants looked in great health though, and seem to like Melbourne Gardens.

Like much of the New Caledonian flora, some populations in the wild have been lost through the land clearing and heavy metal runoff associated with nickel mining. Although commonly found on nickel-rich ultramafic soils, the pretty Metrosideros laurifolia is not under threat for now. It also grows on volcanic soils that may be its saving grace.

In a twitter post a few years ago, Peter Symes, once a colleague here at Royal Botanic Gardens Victoria and now Curator of Cooktown Botanic Gardens in far north Queensland, said Metrosideros laurifolia grows better when the right soil fungi (mycorrhiza) are associated with its roots. I think this comment stemmed from research into propagating the species for rehabilitation of New Caledonian mining sites. 

While on the subject of fungi, it seems the species is susceptible to myrtle rust which occasionally passes through both our sites. 

Still, in the right conditions, and with the right fungi, it can grow to 20 metres tall. Often though, it is a large shrub at best. Our specimens are about two metres high and wide, falling into the sizeable shrub category (so far). 

They are all growing, appropriately, in the New Caledonia bed on the south-west side of Nymphaea Lily Lake.