River Red Gums; Australia's tree?

Well, if pushed I would have to say that they're my favourite Australian tree at least! For me, this mighty tree represents the Australia that I love most, the essence that makes me feel so very priviliged to have been born here. This is another in an irregular series on Australian trees - other recent ones here and here.

Even if you've not visited, it is quite possible you've seen the tree in art - great Australian landscape painters including Albert Namatjira (see an example here) and Hans Heysen (here) featured them repeatedly. It is the only eucalypt found in every mainland Australian state and territory, always following the waterways, and absent only from the deepest deserts and the coastal strip.

River Red Gum Distribution, courtesy of the Atlas of Living Australia.
The actual distribution will be more continuous than this - each dot represents a specimen or record.
(The apparent dot in Tasmania will represent a planted specimen.)

In the mighty Barmah forest of the Murray River which divides the states of Victoria and New South Wales, the red gums form a great forest 25 kilometres wide, of trees up to 40 metres tall. Along the desert watercourses the 'forest' is only one or two trees deep, and the trees rarely exceed 25 metres in height.

Trephina Gorge, East MacDonnell Ranges, Northern Territory.
Every tree in this photo is a River Red Gum.

A River Red Gum forest growing in a rainfall of 400mm a year has a biomass similar to that of a forest with a rainfall three times as much; the key to the red gum forests are the underground waters, and flooding. The trees above benefit from both. 

Floods are essential for seed distribution too, downstream and out onto the flood plains. Seed production is vast - it has been estimated that one tree can produce 150 million seeds in its lifetime - but obviously enough most of this bounty never germinates. Ants account for a huge proportion of the production.

River Red Gum seedlings, Ormiston Gorge, West MacDonnell Ranges, Northern Territory.
Whether these seedlings survive will depend on the timing and ferocity of the next storm-flood.

The trees in the following photos were once such seedlings germinated in the dry river bed. (Don't be fooled by the 'road' in the middle of the river in the first pic - that's normal in these parts!)

Hugh River, Owen Springs Nature Reserve, central Australia.

Stephens Creek, north of Broken Hill, far western New South Wales.

The limits of past floods can be seen in the lines of Red Gum saplings that grow on the flood-plains where the receding flood left them.

River Red Gum saplings, marking a past flood peak, Hattah-Kulkyne National Park, north-western Victoria.

Big River Red Gums are old!! It is estimated that the growth rate of a mature tree is less than a centimetre of diameter a year. Consider some of these magnificent old-timers, and what they've seen.

Melrose, southern Flinders Ranges, South Australia.
 I love the way the road goes around it!

Orroroo, South Australia.
This venerable tree has a circumference of more than 10 metres and is estimated to be over 500 years old.

Brachina Gorge, central Flinders Ranges.

Burra Gorge, South Australia.
The trees here are probably the oldest I've seen; some of them must be close to a thousand years old.

It is remarkable that any trees this old survive, given the extraordinary pillaging that has taken place from the nineteenth century to today. River Red Gum timber is superb, hard and dense - so dense in fact that it doesn't float and had to be transported by barge, and so hard that in the earlier days blasting powder was used to split it. It is proof against rot and insect attack, so hundreds of thousands of trees went to make jetty piles, railway sleepers, fenceposts, wharf pylons and mine props. 25 tonne logs were cut, from trees that are claimed to have been 1000 years old. Worse, it makes excellent firewood, and probably millions of trees went into the fireboxes of the paddle-steamers, and the fire-places of Melbourne and Adelaide homes, which still burn it. Cutting wood for the river boats was a boom job. An average boat burnt a tonne an hour.

The common name refers of course to the timber, rather than the tree itself - here in Australia we have long suffered from an inability to see the trees for the wood. 

The scientific name is rather more intriguing. It was named E. rostrata ('beaked', for the little bud caps) by German botanist Diederich Franz Leonhard von Schlechtendal in 1847, and was known by that very sensible name until the 20th century, when it was realised that von Schlechtendal had actually been beaten to the punch. Back in 1834 Friedrich Dehnhardt, botanist of the Naples Botanic Gardens (or possibly chief gardener at the gardens belonging to the Count of Camaldoli - some of the fine details of the story vary according to your source) described a eucalypt growing in that garden. It has been claimed that it derived from seeds sent by botanist-explorer Allan Cunningham from his 1817 trip to central New South Wales - certainly plausible. Anyway, Dehnhardt named it camaldulensis, the '-ensis' being a standard suffix denoting a place of origin, but his publication promptly sank from sight. (At one stage in my youth I spent some time searching gazetteers for the place, which I decided must have been somewhere in Queensland. I failed.) Why he should have thought it was appropriate to do so from this source, and how he was sure it had not been already described, I cannot imagine. In 1902 Joseph Maiden of the Sydney Botanic Gardens found the name, but regarded it as a synonym of rostrata, and published it as such in 1920. It was William Faris Blakely, one of Australia's great amateur botanists, who pointed out in 1934 that precedence must always rule in taxonomy - quite rightly of course, or anarchy would prevail - and so camaldulensis it is.

Enough of all that, mere human conceit. This is a truly wonderful species of tree, and if you're not familiar with it yet, then you're not familiar with my Australia at least...

River Red Gums,Murchison Gorge, Kalbarri National Park, Western Australia.

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