Mulga: the classic tree of the outback

Mulga country [photo by Bruce Maslin]

As a child just learning to love the sound and rhythms of poetry, I can still remember my mother reading Banjo Patterson's poem Mulga Bill's Bicycle to me. Indeed, I made her read it so many times that eventually I knew it by heart.  This was useful in later years when I could recite it to my children and later still to my grandchildren.

As ‘everyone’ knows, Mulga Bill was an old stockman who had spent his life droving and herding sheep and cattle from a horse’s back. The story takes place about the turn of the 19th century, at about the time when bicycles were just becoming popular. So, it was Mulga Bill …

                      … from Eaglehawk, that caught the cycling craze;

He turned away the good old horse that served him many days;

He dressed himself in cycling clothes, resplendent to be seen;

He hurried off to town and bought a shining new machine;

There was a snag, however:

… as he wheeled it through the door, with air of lordly pride,

The grinning shop assistant said, "Excuse me, can you ride?"

Bill was affronted:

"See here, young man," said Mulga Bill, "from Walgett to the sea,

From Conroy's Gap to Castlereagh, there's none can ride like me.

I'm good all round at everything as everybody knows,

Although I'm not the one to talk - I hate a man that blows.

But riding is my special gift, my chiefest, sole delight;

Just ask a wild duck can it swim, a wildcat can it fight.

There's nothing clothed in hair or hide, or built of flesh or steel,

There's nothing walks or jumps, or runs, on axle, hoof, or wheel,

But what I'll sit, while hide will hold and girths and straps are tight:

I'll ride this here two-wheeled concern right straight away at sight."

Then, as every Australian (worth their salt) knows, there followed a dramatic adventure, with Bill astride (but not in full control of) his shiny new machine … and an undignified finale in the Dead Man’s Creek.

The Mulga Bill 70c stamp from Australia Post’s Bush Ballads series (a gift from forester/philatelist Gary Bacon). Bill is indeed “resplendent to be seen” …

All of this is a self-indulgent diversion from the real topic of this story: the Australian tree called ‘mulga’, a classic, indeed an icon, of the outback. It was many years after my childhood that I first came to associate the name 'Mulga Bill' with the mulga tree, and I was in my 30s before I first ventured into mulga country, way to the north and the east of the Western Australian farming districts.  It was then that I discovered that mulga is Australia’s most widespread native tree, found over vast areas of the inland, the principal tree (and some might say the very soul) of our arid and semi-arid lands.

The distribution of mulga – Australia’s most widespread tree

My first field trip into mulga country, however, was botanically perplexing. Although they were all called “mulga” (botanical name Acacia aneura), individual mulga trees varied enormously in appearance. Some were upright with their arms held up to the sky, others were weeping, still others looked more like a coniferous Christmas tree than a native of the Australian bush. Only the beautiful little yellow wattle blossoms seemed to be uniform on all the variants.

This is the “Christmas Tree” mulga (Acacia aneura), sometimes also known as “Pine Mulga” and …

… this is Blue Mulga, a completely different-looking tree, but still named, back then, Acacia aneura. (photograph by John Fox)

I was discussing this bemusing situation one day with my good friend Bruce Maslin, the world’s premier Acacia botanist. He fingered his wispy beard, paused, and then announced with the fervour of the plant taxonomist about to hit the research trail: "Roger” he said, “It is my greatest ambition to crack the mysteries of mulga."

Well, Bruce eventually did crack those mysteries and has published a book in which he identifies twelve separate species, all called mulga, but each with its distinguishing scientific name.  I managed to get hold of seedlings of quite a few of them (including the Christmas Tree variety) to plant on our property at Gwambygine.  They have developed nicely and add an extra dimension of interest to the original mulga (still Acacia aneura) I planted about 30 years ago and which has grown splendidly.

What do we know about mulga?

Firstly, it is not a glamorous tree. I don’t think I have ever seen one planted as an ornamental in park or garden. It does not have dramatic blossom, glittering foliage or bark that changes colour with the seasons. Up close, the leaves (OK Bruce, they are not really leaves, but phyllodes) are a pleasant olive/blue colour. The tree crowns are usually sparse and throw little shade, especially the variant with fine, narrow foliage. The bark is black, rough and deeply fissured. Compared with, for example, gimlet, marble gum or salmon gum, some people (Philistines all) would regard a grove of mulga as drab and uninteresting.

A typical mulga, unprepossessing, but tough and self-sufficient. It is growing on shallow rocky soil in association with spinifex – one of the harshest sites imaginable.

Nevertheless, there is beauty to be found in mulga country.

Moonrise over mulga in the Gibson Desert (photo by Ian Kealley)

And there are many things to love about mulga.

First it is tough. It can survive years of almost zero rainfall in the Pilbara, the central deserts and in western NSW and south-western Queensland.  It seems to be able to hibernate until the drought breaks. And because the tree trunk is deeply fissured and shaped like a funnel, it can capture the merest molecule of passing moisture and channel it down to the roots. Not only is it dry, but mulga country is broiling hot in summer and gets down to minus-zero on frosty nights in winter. Despite the harshness of these conditions, and in the absence of high intensity bushfires, mulga trees will live for hundreds of years – indeed one of the Aboriginal names for mulga (of which there are many) is Umoona which means “long life”.

The second thing I love is the way the tree looks after itself. In a run of good seasons, even in the presence of grazing, mulga regenerates prolifically. The seeds remain alive in the soil for decades and will burst into life the moment conditions are right. I have seen places in the Pilbara where, after grazing by sheep was discontinued and a cyclonic downpour, thickets of mulga saplings sprang up in all directions.

Mulga is adaptable. While it is most plentiful on floodplains, sandy wash-plains and broad valleys, it also grows on stony ridges and in the swales between sand dunes. In fact, it does not seem to matter where you step down from your camel (or out of your Toyota Prado) in arid Australia, there will be scattered individual mulga trees, or a grove of them, somewhere nearby.

Fire and mulga

When it comes to fire, the situation is complex. As Neil Burrows (incomparable fire ecologist and scientist of the outback) points out:

Mulga is widespread and occurs on a range of different soils in a wide range of vegetation types. Where it is growing on bare, shallow, stony soils, fires almost never occur – I have studied mulga landscapes in the Murchison that have never been burnt (as far as I can tell) and couldn’t burn because of the complete absence of fuel.  But it is different where mulga is growing on more fertile and moister soils. Following good rains these sites develop a dense ground cover of soft grasses and herbs. When this cures, it will carry a fire of lethal intensity, killing every mulga tree in its path. The next rains then bring up a ‘wheatfield’ of mulga regeneration, germinating from soil-stored seed. So long as these areas do not burn again for a sufficient time for the new trees to flower and produce seed, mulga survives.

Mulga growing on stony ranges “well off the beaten track”. (photo by Don Burnside). Fires will run through this country from “rare to never”.

Finally, Neil has commented on those puzzling sites where groves of mulga are found growing interspersed with spinifex, the latter being highly flammable under the “right” conditions.  Mulga will only survive fire in this situation if the fire is mild and patchy (as will occur when the spinifex is young and green), and the day is cool and windless. Mulga’s thick bark protects the tree against a trickling fire, but not against a raging summer blaze.

How well this story reinforces a second story: that of the way the Aboriginal people skilfully used fires of mild intensity, lit on the right day, so as to pre-empt the damage from a violent fire on the wrong day … and in so doing ensuring that mulga (which they valued highly) was protected.

The Aborigines revered mulga

Indigenous Australians long revered mulga for its utility and versatility. The wood was used for tools and weapons, the foliage for medicinal purposes, and the seeds for nutrition. Aboriginal people lived happily in mulga country for thousands of years.

Mulga seeds were especially prized. They were either eaten raw, ground into flour and baked into seedcakes or roasted and mixed with water to make a high-protein, high-fat paste with the consistency of peanut butter.

They collected and ate ‘mulga apples’ – not a fruit, but an insect gall about the size of a golf ball, often containing a tasty grub. They also collected and chewed the gum which exudes from wounds on the trunk and relished the sweet honeydew produced by lerps on mulga branches. Honey ants, one of the great bush tucker delicacies, are often found on and around mulga when the trees are in flower.

An unusual use of mulga was in “smoke therapy” (a modern term). The green foliage of a mulga tree would be set to smoulder, and the smoke used to relieve sick babies and to calm young children.

[An aside: I wanted to try this one day on my little grandson Will who was staying with us at Gwambygine for a while. He was a dear little boy, but seriously boisterous. Mulga smoke therapy might have helped calm him, I thought (which, in turn, would have calmed me), but the Everloving persuaded me that it was too risky, it being a hot day in mid-summer, not the time for lighting fires. The treatment was never administered.]

Mulga wood is remarkable for its strength and its capacity to take a point and an edge. Aboriginal people of course knew this, which is why mulga timber was favoured for spears, the slim saplings coming away after a bushfire being de-barked, stiffened and hardened in the campfire and then pointed, or tipped with a sharp bone head. Mulga was also fashioned into digging sticks, woomeras, and shields. Wooden bowls were made which would carry water.

Historian Geoffrey Blainey has an interesting comment on water and mulga:

In dry regions the local Aborigines knew where to find water at nearly every time of the year. That they had been able to survive for so long in this dry land puzzled the [European] newcomers.

The reasons for their survival in the deserts slowly emerged. In the dry country certain trees yielded water. The mallee, especially the red species, yielded water after its long roots were excavated and broken open. A particular she-oak produced water. In the trunk of the spotted gum, small hollows often carried water. In the mulga country of Western Australia, a tree not unlike the mulga was known as the water tree.

[As we now know, the ‘water tree’ described here was not mulga, but more likely the desert oak, about which I have written elsewhere in these chronicles. See:

https://www.forestleaves.blog/post/desert-oak-an-icon-of-inland-australia ]

Mulga wood

In addition to its many traditional uses, mulga has beautiful timber. The sapwood is yellow and the heartwood a deep, dark brown/red, sometimes almost black. It is extraordinarily heavy (one of the heaviest timbers in the world) and takes a glorious polish.

A freshly cut piece of mulga showing the superb colour in the heartwood. Photo by Ian Keally

Once it is dry, the timber weathers to a consistency and resilience of cast iron, and the most eager termite cannot make a dent in it. I have seen mulga fence posts out along the Trans-Australian railway line that date back to 1914 and are still as sound as the day they were put in the ground.  The original mulga posts on the Number One Rabbit Proof fence, constructed even earlier, are still intact in many places.  Over time, the sapwood bleaches white, but the heartwood retains its rich colour seemingly for ever.

I was discussing this with Don Burnside one day (he is the doyen of the rangelands) and he mentioned the stark white dead mulga that you often see dotted through the bush. Don thinks these trees may have been “standing dead” for hundreds of years.

Remnant section of the No 1 Rabbit Proof Fence, near the WA south coast, the original mulga posts still sound after 120 years in the ground. Photo by Jack Bradshaw

Mulga country has a further quality that should be mentioned. Neil Burrows, who grew up in the Murchison, has written about "the sweet smell of the mulga after rain", something that always reminds him of his childhood, running amok with his mates in the bushland near Boogardie. I have only ever been in mulga country when it has been hot and dry, but as I love the aromas of the bush, Neil’s words draw me into a trance of imagination.

These days one of the most popular uses for mulga is as tourist mementos, such as boomerangs, mountings for thermometers, desk ornaments.  It has also been used with success for manufacture of mouthpieces for woodwind instruments like flutes, clarinets and oboes, or fretboards for guitars.  I have a beautifully turned ornament cut from a post from an abandoned section of the Rabbit Proof Fence on my desk as I write.

A superb little ‘whisky flask’ made from a mulga fencepost

When the tree is alive or freshly felled, mulga can be cut easily with a sharp axe or drilled with a brace and bit. Thousands of tons of mulga were once cut for pit props and firewood for the gold mines in the Murchison and northeast Goldfields. I once worked with an old Forest Ranger who, as a young man during the Depression, had been a firewood cutter in the Murchison, producing fuel for the gold mines at Yuanmi and Sandstone. “Over the five years I was there” Frank told me, “I must have chopped down and trimmed half a million mulga trees, just on my own. And there were about 20 other cutters working for the same mines at the same time".

Mulga trees do not usually coppice (re-shoot from the stump) so the fact that mulga is still prolific in the areas where Frank and his mates were at work in the 1930s, demonstrates its ability to regenerate from seed after disturbance.

Mulga makes wonderful firewood, but you risk spoiling a good axe if you have a go at the dead timber for your campfire in the bush.  I once found (or at least I imagine I found) some good evidence of this. The Everloving and I were exploring auriferous country way east of anywhere and, walking through a grove of mulga trees, I spotted something on the ground, half-buried, that looked interesting. What I dug out turned out to be an old axe-head. It was rusty, pitted and was missing large chunks of its blade.

The old axe head found in mulga country. (Ignore the handle, this is just a bit of bush timber I put in so I could hang the axe on a hook in the shed)

Nobody knows the real story. But I liked to imagine an old prospector, maybe a century or more ago, deciding to camp among the mulga trees and striking a blow at a convenient log for firewood for the campfire … and then his disgust as he threw his mangled axe away. I have heard it said that old dry mulga is “tougher than steel”, and I like to think this artifact proves the point.

Anyway, I never attempt to chop dead mulga. My approach is to gather up bits and pieces of old limbs under a tree and use these. They make a perfect campfire.  There is nothing quite like a goat casserole cooked in the camp oven over the slow-burning coals of a mulgawood fire.  Then, after you turn in, the wood will throb away slowly all night, and with the addition of a few dry leaves will burst into flame to boil the morning billy.

Rangelander John Morrissey in mulga country near Mt Magnet – a few old bits and pieces of dry mulga, a few dry leaves, one match, and the result is a campfire that will burn all night. (Photo by Don Burnside)

As one early bushman put it, remembering his time as a stockman on an inland sheep station (I quote here from the 2016 Australian National Dictionary): We always used as firewood a species of Acacia, known as mulga. It … gives out intense heat. No wonder bush blacksmiths in the early days prized mulgawood for making charcoal for the forge.

But mulga scrubland could also be dangerous to horses and stockmen, especially after a bushfire had been through the area. As the poet 'Ironbark' warned, there was always a risk of being staked:

You stockmen from the Murray's side,

Who through the mallee boldly ride,

Beware the mulga stake!

'Tis strong and tough as bullock-hide,

Nor like the mallee turn aside;

But in its savage sylvan pride

Will neither bend nor break!

Harry ‘Breaker’ Morant also wrote about mulga country in the bush poem in which he laments the conversion of an outback station from cattle to sheep:

 … they've built brush-yards on Wild Horse Creek, where in the morning's hush

We've sat silent in the saddle, and listened for the rush

Of the scrubbers - when we heard 'em, 'twas wheel 'em if you can,

While gidgee, pine and mulga tried the nerve of horse and man.

Cattlemen may not have liked riding their horses through mulga country, but they valued mulga, nevertheless. On moister more fertile soils, mulga becomes quite ‘leafy’ and the foliage is relatively high in protein, and palatable to stock. Feral goats will climb a mulga tree to get at the foliage, and in droughts in western NSW and Queensland, the cattlemen lop the trees or even bulldoze them to provide fodder for their herds. I worry about this, as it would be necessary for grazing to be suspended to ensure regeneration, and I am not sure this is always done. On the other hand, as we have seen, when it comes to survival, and recovery after rough handling, mulga is as tough as they come.

Mulga bloom

Mulga is a wattle, and has lovely yellow flowers, hanging in tassels.  There is no “flowering season” – the tree responds to rain, which means that in a drought year it may not bloom at all.

Blossom on blue mulga in the Clutterbuck Hills. Photo by Steve Hopper

The blossom is surprisingly dainty for a rugged inland tree. They make a bright splash of colour in the bush on a winter's day and are the source of that “sweet smell of the mulga”, as Neil Burrows puts it, the memory of which lingers in the minds of all who have enjoyed it.

This is summed up in the memorable description of mulga country by H.H. Finlayson in his wonderful book The Red Centre. Writing about Central Australia in the 1930s, Finlayson says:

In this virgin country the mulga, both in its bushy and arborescent forms, is an attractive symmetrical plant, very different from the tortured, twisted remnants which survive the persecution of stock in the occupied areas. Like most plants of the Centre, it blooms after heavy rain, apparently largely independent of the season of the year. The flower is a little golden-yellow bottlebrush, deliciously scented, and when a rainstorm has raised new life in hundreds of square miles of mulga parks, the expanse of blossom and its perfume are things not easily forgotten.

Finlayson goes on to remind us that the name of the famous opal-mining town in central Australia, Oodnadatta, means "mulga bloom" in the local Aboriginal dialect.

An “attractive and symmetrical” mulga tree in the central desert. This photo by Andrew Mitchell is on the cover of a book on the plants of the arid shrublands by an admired friend, the late David Wilcox. The tree has a remarkably dense crown, probably meaning that the photo was taken after good rains.

 A quick word on the Mulga Parrot and the Mulga Snake

The mulga parrot, so-called because it’s usual habitat is the mulga woodlands (and also perhaps because it nests in hollows in mulga trees,) is one of Australia’s most beautiful birds. Indeed, one of the bird’s alternative names is “The Many-Coloured Parrot” … far too prosaic a name for my liking. Most Australians have never seen one (outside of an aviary, that is), as it occurs only in the most remote outback.

I have never knowingly seen a mulga parrot (I have a poor eye for birds) but my colleague Ian Kealley tells me that they are common in mulga country – he sees them every time he is out there. They forage on the ground in small flocks or pairs and take off with a flash of colour when disturbed.

I like the association between the mulga tree and the mulga parrot, it is a sort of beauty and the beast thing, quite a common phenomenon in the Australian bush.

Mulga parrot. The illustration is from “Australian Birds” by Robin Hill

The mulga snake on the other hand (also known in WA as the King Brown) is one of the deadliest in the world. Snake enthusiasts describe it as a beautiful animal, but I will be happy if I never see one.

Another quick word: mulga and mistletoe

Many trees that grow in arid Australia are parasites or semi-parasites (for example sandalwood and quandong) and many others are themselves parasitised, especially by mistletoes. It is a sort of cooperative arrangement that assists survival in arid country.

I was in the bush one day with expert naturalist Tony Start, somewhere in wild Pilbara country, and he pointed out that nearly every mulga tree nearby had mistletoes growing in their crowns. Tony is an authority on mistletoe, and it was not long before I heard about the two species of mistletoe that specialise on mulga, one of which is actually called mulga mistletoe (the other is pincushion mistletoe). Although the mistletoes are parasites, drawing water and mineral nutrients from their mulga hosts, they do not appear to debilitate the host tree in any way. The live happily together, seemingly for ever.

Tony also mentioned:

Many mistletoes are used by butterflies and other insects as larval food plants. Strangely, none are known to use the “mulga mistletoe” for food, but Amaryllis Azure, a striking butterfly with shiny blue wings that featured in an Australian postage stamp series, often feeds on “pincushion mistletoe” growing on mulga.

Australian stamps featuring the Azure Blue butterfly, often found on mistletoe on mulga trees

Mulga conservation

The main threat to mulga is no longer harvesting for firewood, mining timber or fence posts, but high-intensity wildfires (especially in areas where the introduced and highly flammable buffel grass is prevalent), grazing by sheep, feral goats, rabbits and wild camels, or being cut for cattle fodder in areas affected by drought. 

There are also concerns in the Pilbara where iron ore railways and haul roads cut through mulga country, disrupting drainage patterns and drying out and droughting stands of mulga.

Apart from improved and upgraded railway and road engineering, the two most critical things we could do to conserve mulga are (i) replacement of large hot summer bushfires by cool, patchy burns; and (ii) control of feral herbivores in inland Australia. Wherever these two things are done mulga recovers and thrives, demonstrating again the tough resilience of this wonderful tree. Whether either can be achieved at the necessary scale is one of the great conservation conundrums in modern Australia.

And what of Mulga Bill's bicycle?

.. It's safe at rest in Dead Man's Creek, we'll leave it lying still;

A horse's back is good enough henceforth for Mulga Bill.

References

Blainey, Geoffrey (2003): Black Kettle and Full Moon – daily life in a vanished Australia. Penguin Books

Burows, Neil D (2019): Children of the Convicts. iprintplus, Perth Western Australia

Finlayson, H.H. (1952): The Red Centre - man and beast in the heart of Australia. Angus and Robertson, Sydney

B. R. Maslin and J. E. Reid (2012). A taxonomic revision of Mulga (Acacia aneura and its close relatives) in Western Australia. Nuytsia 22(1): 129-267

Wilcox, David and Andrew Mitchell (1994): Arid Shrubland Plants of Western Australia. University of Western Australia Press.