Tuesday, 25 August 2015

Beaked buds by a billabong

Back in the early years in this blog (November 2009) I wrote about the River Red Gum being split into seven subspecies, river red gumlets I christened them. In that post I talked about how the species name, camaldulensis, comes from the name of a garden in Italy.

That garden was L'Hortus Camaldulensis di Napoli and its head gardener and German botanist, Friedrich Dehnhardt. In 1832, Dehnhardt described and named the River Red Gum Eucalyptus camaldulensis from plants growing in this private botanic garden just out of Naples.

For a hundred years though the name Eucalyptus rostrata was used for River Red Gum, at least in Australia. We can thank another German botanist Diederich Franz Leonhard von Schlechtendal for this name, which he published in 1847. What we can't think him for is is lack of scholarship. Not only did Schlechtendal miss the fact that the River Red Gum already had a name, but he also overlooked the fact that species name he chose to bestow upon it was already taken, by the Swamp Mahogany.

Fifty years earlier, in 1797, the Spanish botanist Antonio José Cavanilles had named the Swamp Mahogany Eucalyptus rostrata. Sadly that application of the name rostata has also been relegated to what we call a synonym, with the Swamp Mahogany being named Eucalyptus robusta two years earlier, in 1795, by the English botanist James Edward Smith.

Generally in plant plant nomenclature, the earliest described name is the correct one: for Swamp Mahogany, Eucalyptus robusta and for River Red Gum, Eucalyptus camaldulensis. While we might gain a quaint historical vignette through using the Italian name we lose a little in the identification stakes.

'Rostrum' is Latin for beak, and compared to most other species of eucalypt, the 5-10 clustered flower buds of the River Red Gum are 'beaked'. Other buds are longer and narrower (many are like clown hats) and some are short and nipple-like (which is how I would describe those of the Swamp Mahogany as it happens, so the name rostrata would have been wasted there!). Few would be confused with the pointy-beaked buds of Eucalyptus rostrata... whoops, Eucalyptus camaldulensis.

The cap - whether extended, beaked, nippled or simply domed - replaces the petals (and in this case the layer outside the petals, called the sepals, as well), and is the source of the genus name 'eucalyptus', meaning well covered, a reference to way this 'operculum' protects the flower until it is shed revealing a brush of stamens (the male parts of the flower bearing pollen).

The other distinguishing feature of the River Red Gum is the way the disc around the top half of the fruit (the gum nut) curves upwards and inwards. Eucalypt fruits also express themselves in a range shapes, sizes and analogues.

One of most cherished books as a young botanical student was Eucalyptus Buds and Fruits: Illustrations of the buds and fruits of the genus with a list of authentic specimens from which the drawings were made, edited by George Chippendale. Yes a very nerdy book for a nerdy 18 year-old just becoming immersed in the plant world after dumping physics and maths in first year university. I went straight to it the other day when I discovered these and other fruits and buds beside the Yarra River in Hawthorn.

But if you don't want to look this closely the other diagnostic characteristic of the River Red Gum is where it grows and how common it is. If you see a gum-barked (apart from the base) tree growing next to a river, creek or billabong in mainland Australia, it's most likely this species. Or less commonly a Swamp Gum, Manna Gum or maybe Candlebark... but their buds don't have beaks.

The last thing that singles out a River Red Gum, often, is its ability to survive and to wear its scars. It is not always a classically beautiful tree but it can be a resilient one. Which is a certain kind of beauty in itself.

Images: Except the last (which a remnant in the town of Buninyong, near Ballarat, photographed in June 2015) the pictures are of a few relatively young trees planted beside the Yarra River, taken in July 2015.

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