Recreating the Country blog
Black Wattle, Acacia mearnsii
Turning up the heat.
Our first home in country Victoria had an old IXL 72 wood-stove. These wonderful cast iron stoves were made in Geelong, which was very handy when I needed replacement parts for repairs. It became the focus of our cosy kitchen environment, providing winter warmth as well as hot water. Many an evening I sat in front of that stove after a cold winter’s day in the nursery. The firebox door open, the fire crackling, the flames flickering and my cold feet parked in the open plate warmer under the oven. Heaven!
The point of this recollection is that the old stove also made amazing pizzas when fired-up with Black Wattle firewood. The stove would glow with the heat and would have to be cooled by adding eucalypt firewood once the pizzas were cooked.
It was far too hot to sit near and the intense radiant heat could be felt on the other side of our open-plan kitchen. It was the hottest firewood we burnt by far. Hotter than River Red Gum and Sugar Gum which are both very popular hot burning firewood’s.
Commonly pronounced - mare-n-see-I.
The origin of this name isn’t clear but may come from a district near the Grampians in Scotland called Mearns. Black Wattle is indigenous to the Victorian Grampians (as well as southern Australia and Tasmania).
Note: The Grampians is now called Gariwerd, the traditional name of the Djab Wurrung and the Jardwadjali people
Some human context – many uses
One of the fastest growing plants that I have had the pleasure of planting on farms is the Black Wattle. If growing fast was an Olympic event for trees then the Black Wattle is the Usain Bolt of the tree world.
I remember saying to customers with the certainty of experience, ‘plant a Black Wattle today and harvest a tonne of firewood in 5 years’. And I wasn't exaggerating.
It’s not unusual for a Black Wattle to reach 1-2 meters tall in twelve months and 8m in five years. At maturity it can reach well over 10m tall and wide.
Black Wattle will start to senesce (die back) after 15 years though they can remain healthy for over 20 years in well drained loamy soils. In heavy clay soils they tend to be much shorter lived.
Its remarkable growth rate has other benefits/uses. In forestry, growing valuable timber species in frosty locations like Spotted Gum, Corymbia maculata and Sugar Gum, Eucalyptus cladocalyx is very difficult. Just a couple of mild frosts will kill them. So it’s the frost hardy Black Wattle to the rescue, planted as a ‘nurse’ tree one year in advance.
In one year Black Wattle will provide enough shelter to protect a frost tender seedling planted close by under its leafy canopy. A few years later the Black Wattle is cut off at ground level when the frost tender tree is big enough to manage on its own (usually over 2 m tall). Cutting off the wattle also releases lots of nitrogen from its roots, feeding and accelerating the growth of the timber tree.
I have a friend who has milled the timber from mature Black Wattles to make lining boards for his pantry. The boards are a beautiful dark red-brown colour (click here to see a sample of the wood). Cutting and drying them for this purpose is a bit tricky as they have a tendency to crack and twist.
See this link to an amusing story about black wattle lining boards - Richards Sweet rewards
Australian Black Wattle is also grown as an important crop in South Africa. There they remove the bark to produce tannin for the leather industry. It was also in demand for its tan-bark in Melbourne's early years
The Tan, a scenic walk around the Melbourne Botanical Gardens, gets its name from wattle tan-bark. In Melbourne, tan-bark was reused from the many tanneries (mostly Black Wattle) to provide a clean walking surface around the Botanical Gardens and Melbourne’s muddy streets, churned up by bullocks, horses and carts.
The Traditional Owners of the southern regions of Australia also ate wattle sap as an source of energy. Oozing Black Wattle sap/gum, called kino, forms into soft round lumps on the side of large branches and the main trunk. It's natures original gopstopper which can be pulled off and eaten as an energy rich food. It's quite chewy and has a subtle sweetness that is very enjoyable.
In nature Black Wattles provide a range of goods and services for wildlife;
Bronzewing Pigeons are often seen searching for wattle seeds under Black Wattles. For them they are an important source of protein, valued also by cockatoos, rosellas, parrots and wattlebirds.
I have often watched with delight a Grey Fantail darting from a Black Wattle canopy. These agile small birds provide a wonderful acrobatic display as they fill their bellies with flying insects attracted by the wattle’s foliage. A Melbourne study identified sixty species of moths on wattles generally, which are also an important food plant for butterflies.
Long-billed Corellas & Sulphur Crested Cockatoos will litter the ground with Black Wattle leaves as they nip them off to feed on the sweet sugary sap. This flows at flowering times to attract birds that unwittingly spread the wattle pollen on their wings providing a pollination service for the wattle tree.
Honeyeaters and thornbills are also lured by the promise of a sweet drink. They lick up the sap as it oozes from glands located along the centre spine of the Black Wattle’s ferny leaf. Ants, native bees and wasps are also attracted to the sugars produced by wattle glands during flowering.
The aril attached to the wattle seed is rich in polyunsaturated oil. This attachment is designed to attract ants that carry the seed away and bury it underground. This is the ideal place to store the seed where it will last for centuries in this cool dark environment.
The scratching and digging of an echidna around the ants nest is enough to bring the buried seed to the surface and prepare it for germination following a good rain.
Attracting Sugar Gliders to your garden/plantation
Sugar Gliders are in greater density when there are more Black Wattle trees. The gliders scratch the wattle bark and ‘milk’ the oozing sap. This sap is a rich source of energy critical to the survival of glider family groups. So much so that they hotly defended their wattle trees from other gliders.
Gliders eat an estimated 3+kg of insects/year, so they can be an important agent in the control of insect numbers. To attract gliders to your property, provide some suitable tree hollows for them to sleep in during the day and large wattle trees to feed in at night.
Black Wattles and other plants
All wattles fix atmospheric nitrogen in the soil. This benefits neighbouring plants as long as they can access enough soil moisture. Wattle ground covers and shrubs can be an asset in a garden providing this nutrifying benefit.
Though survival for other plants growing near mature Black Wattles becomes a supreme struggle. Their root systems tenaciously suck-out all the available soil moisture around the tree. This eventually becomes a bare zone under trees where only the toughest shade tolerant native grasses and lilies will grow.
In sustainable biodiversity (biorich) plantings it’s wise to plant Black Wattles in small clumps and in wide plantations up to 50/clump. This provides a concentrated source of food for wildlife and results in excellent pollination and seed production. It also makes it convenient to thin or harvest firewood. ‘Natural Selection’ then will determine the strongest and fittest trees for the future if the most vigorous trees are left to mature.
Advice for those who like it hot
Though it is very hot burning, I can remember having mixed feelings about cutting Black Wattle for firewood. It tends to blunt a chainsaw more quickly than eucalypt, though this is much less noticeable when it’s cut green.
The sharp ends of damaged branches are an eye hazard and should be removed with an axe or chainsaw after felling. Consider wearing safety glasses if there are a lot of long branches. Once cut into short blocks it is easy to split with an axe either green or dry.
To read more about Black Wattle click to the Australian Plants Societies description
Propagation from seed
As with other wattles the trick to germinating Black Wattle seed is to soften or scratch (scarify) the hard seed coating. Softening is conveniently done by pouring boiled water over the seed. Allow this to cool, pour off the excess water then sow into a well drained seed raising mix. Cover the seed and then prick the seedlings out when they lift their heads above the seed bed. This is my preferred method because its fast and causes no damage to the root system which is just a single shoot at this early stage.
Inoculating the seedlings with rhizobia after sowing into seedling trays makes the young trees stronger and more vigorous. To read about this method go to my blog on acacias. Click here and scroll down to read more.
The lure of gold dust
Since it was first discovered in central Victoria in 185o, gold-dust has played significant part in the modern history of Australia. Thousands of hopefuls arrived on our shores prepared to live rough and make huge personal sacrifices in the hope of finding something yellow and precious. Even small quantities of gold dust would make fossickers jump for joy in paroxysms of pleasure. Though I started my working life as a geologist I could never fathom this obsession with gold.
In my early thirties I discovered native plants and realised that the gold dust that excited me wasn't found in stream sediments or deep underground. It's more easily found tantalizingly above the ground in quantities that would fill a gold fossickers bag in no time. It's extraordinarily beautiful and is valued by many more species than just Homo sapiens
Gold-dust Wattle, Acacia acinacea
Commonly pronounced -
Ass-in-ace-y - finishing with a pleasant upward inflection.
Its all Greek – acinacea/akinakes = short curved Persian sword or dagger
Its name refers to the clusters of remarkable and tightly curved small seed pods that form in early December.
Some human context
This beautiful small shrub produces large bunches of wattle flowers in Spring that are perhaps even more golden than Australia’s floral emblem, described in my previous blog. I’ve seen plants so heavy with flowers that they drooped to the ground under the weight. As an added attraction it has small rounded shiny leaves that give it a soft, delicate appearance throughout the year.
This delicate appearance belies its tough drought tolerant character making it suitable for most well drained soils. Like all wattles the Gold-dust Wattle adds nitrogen to the soil which benefits other native plants growing nearby.
An ideal plant for the home garden, though notably heavy pruning can make plants sucker, so a light pruning in small gardens may be preferred.
Its bushy nature makes it very suitable for mass planting as a low shrub layer in larger biodiversity plantings.
For more information on the Gold-dust Wattle click here
Restoring small remnants of Gold-dust Wattle
All wattles need large communities of at least 50 plants with diverse genetics to survive for the long term. In some locations the Gold-dust Wattle is in danger of dying out because of low numbers causing lack of plant diversity and inbreeding.
For example Gold-dust Wattle grows in the Bannockburn Bush and on the road-side between the towns of Bannockburn and Teesdale. These plant communities lack genetic diversity, are isolated (three kilometers apart) and small. The result of this is they produce very little fertile seed. The germinated seed also shows a lot of variation in vigor, a sure sign of inbreeding.
In 2010 the Golden Plains Shire funded the planting of 100 Gold Dust Wattles on the roadside next to the existing remnant community. These plants were grown from seed sourced outside the local area to boost the genetic diversity of this vulnerable plant community. This has lead to an increased production of viable and healthy seed.
The trusses of scented flowers are food for many insects. These flowers are a source of golden pollen and nectar for many native beetles, moths and butterflies.
These insects offer a diverse smorgasbord for insect eating birds. The seeds are food for native pigeons, parrots and quail. Ants also gather the seed for its oil rich aril that attaches the small black seed to the pod.
Insects also eat the seed frustrating seed collectors when they open the pods to find only brown dust inside.
Its bushy form makes it an ideal habit plant for small insect eating birds like the Superb Fairy Wren. Skinks, frogs and small mammals benefit from its low shelter particularly if some logs or rocks are added as part of the landscape design.
To read more about small insect eating birds try this excellent ‘Birds in Backyards’ link
Collecting seed - harvest time is usually late December to early January
The seed found in healthy plant communities is easy to collect because the pods are usually in clusters. With all wattles, waiting until the pods are opening with some seeds visible makes separating the seeds from the pods much easier.
I usually rub handfuls of pods between my gloved hands in a scrubbing motion to detach the seeds. A common garden sieve will aid cleaning by separating the seeds and the pods. Winnowing in a light breeze while pouring the seed from one bucket to another will remove the fine debris leaving the seed clean and ready for storage in a labelled zip-lock bag.
Remember to record the name of the species (a short description is good if you're not sure), where it was collected and the date of collection. Other information such as soil type and aspect is very useful when choosing the best home for your seedlings.
Pouring boiled water over the seeds then allowing them to cool is a convenient method. Seeds can then be sown into a seed raising mix or directly into the soil where they are to grow. Cover to a depth more or less equal to the thickness of the seed. They are a bit slower to germinate than other wattles, taking 2 - 4 weeks.
Germinated seed in trays can be planted in tubes as soon as they appear above the potting mix. This is a quick method that minimises the root damage that can occur when transplanting larger seedlings with more developed fragile roots.
For more information on propagating wattles go to this link and scroll to the end
Stephen Murphy is qualified in Geology and Environmental Management and has been a nurseryman and a designer of natural landscapes for over 30 years. He loves the bush, supports Landcare and is a volunteer helping to conserve local reserves.