Wattles - Evolution in Action

Wattles - Evolution in Action
Family: MIMOSACEAE
Australian acacias had a problem. Their leaves were costing them too much. Plants lose water through their leaves, and as the continent dried out they were being pushed to the wall. A few million years ago, as the ice age advanced and climate change cooled and dried their home ground, the situation became serious. Something had to be done - but the trouble is that plants need those green leaves, to do the essential job of photosynthesis. They capture carbon dioxide and remove the oxygen from it, thus providing the plant with its “food” - a steady supply of carbon.




Typical wattle leaves.
The common local Cinnamon Greenwattle
Acacia irrorata




What the wattles needed was to develop a new way of photosynthesising, so they could get rid of those water-wasting leaves.
Changing the nature of the leaf-stems - the petioles - was the answer. In many species of wattle they became longer, broader, flatter, and full of green chlorophyll, the substance which is essential for photosynthesis. The wattles could then give up making leaves, and hey presto, here was a whole new suite of drought-hardy plants!




Leaf in Transition.
Oleander-leafed Wattle
Acacia neriifolia





Not all wattle species have done it. Some still have leaves, just as their ancestors have always done. We sometimes see them described as the “ferny-leafed” kind of wattle. The others are called “long-leafed”. In reality, they are completely leafless, but their modified leaf-stems, (which botanists call phyllodes), look so like leaves that the difference can be hard to detect.

Growing up. Three leaf-types on one branchlet, Acacia neriifolia

We can still see the evidence of their evolutionary history, though, in young plants. Wattles of the “long-leafed” type begin life with ferny leaves. Then, as they grow, leaves with exaggerated stems appear. The tendency to produce leaves soon disappears, and older plants have nothing but phyllodes.
The toughest, most drought-hardy wattles produce just one leaf, then get down to the leaf-free life as soon as possible. Others, such as Acacia neriifolia, go on producing the half-and-half model until they are more than shoulder-height.
They are a common local plant, so we can see plenty of examples in our local bush. If you want to see some, look for seedlings among the adults which are
looking so spectacular along the top of the range at the moment.


Some wattles evolve even further. Their phyllodes hang vertically, so as to present the least possible surface area to the sun - and their colour has changes to silvery grey, to reflect sunlight. These very tough plants waste little of their lives producing leaf - a single token leaf at birth is all they bother with, before getting on with producing phyllodes. This brigalow (Acacia harpophylla) at right is a typical example of these most drought-hardy wattles.

Oleander-leafed Wattle

Acacia neriifolia
Family: MIMOSACEAE
A rather imaginative person once thought that the narrow phyllodes of this plant resembled oleander leaves.

Be that as it may, this fast-growing, 8m tall plant is one of our district's best wattles,  having a spectacular display of golden flowers in August. Each year, they make a magnificent show on the road between Toowoomba and Crows Nest.















In the bush we see it as a smallish tree, with most of its flowers high out of reach. If used in a garden it responds well to pruning, so can be kept as a shrub. Pruning increases its bushiness, making it a good screen and Oleander-substitute.

Most people don't prune their wattles, though, and species like this one which grow fast and are naturally rather large, but are not long lived (about 15 years), are not popular in gardens. For this reason, we need to encourage its use in suitable spaces - beside highways, in drainage easements, in nature reserves and parks, and on privately owned "acreage estate" residential blocks. If its population is allowed to dwindle, as is happening with so many of our local plants as our suburbs spread ever outwards, our district's character will lose something very important!


Unlike the poisonous, non-Australian oleanders, this is a plant which fits the environment. It hosts a rich population of native insects including some lovely little butterflies, and attracts birds which appreciate the insect supply.

This is a wattle for well-drained soil, such as the snuffy red-soils along the top of the range, and the nearby sandstone soils.

It is frost-hardy, and thrives  through the worst of our droughts with no supplementary watering.

A Drive to Crows Nest

This is something Toowoomba people love to do at this time of the year, when the wattles along the highway are truly spectacular. The species you’ll see most of is the oleander wattle, Acacia nerifolia.
On the way, you can look at the marked trees of “Cathedral Drive” near Hampton, and see what the fuss is all about. There are about 1400 of these trees. They were marked with yellow spots and crosses by the Main Roads Department a few months ago. They planned to remove them for roadworks, aimed at making this accident-prone section of highway safer.
A local action group, which considered that the number of trees earmarked for removal was excessive, has gone along and tied conspicuous pink ribbons around some of the yellow-marked trees, making it easy for passers-by to visualise the scale of the proposed destruction. The group considers that the beauty of this drive has economic importance to all those involved in tourist-related industries, from Toowoomba to Crows Nest. Many of them also just like living somewhere beautiful, (and there’s no doubt that destruction of natural beauty in an area affects residential property values). Cathedral Drive would be providing habitat for a lot of wildlife, especially in those tree hollows, too.
As recent events have shown us, this stretch of road is unsuitable for drivers who are not concerned with enjoying the landscape as they drive, but just want to get where they’re going as fast as possible. We tend to take it for granted that highways should serve this function, Here is a piece of highway which does not.
The roadworks project has apparently been put on hold which the issues are worked out.
Continuing the drive to Crows nest, you can see, north of Pechey, the Main Roads idea of suitable clearing, and a highway which has been made "safe".
Like me, you’ll probably find yourself peering at the steep slopes they’ve created on the highway edges, all unprotected by any sort of railing, and wondering....
Much of the new highway was created from road which was once tree-lined. How would you rank it now - on a scale of 1 to 10 - for landscape beauty?
If you feel strongly about the issue, you might like to time your drive so you can call in at the rally which is to be held at Hampton tomorrow (Saturday August 15.)

Hollow trees and Dropped Limbs

Rubbish - or Environmental Riches?
With the Cathedral Drive issue we are, once again, hearing the argument that hollow trees are “rubbish”, so might as well be cleared.
Wildlife - and those who value Australian fauna - don’t agree, of course. To them, trees only start to get valuable when they start forming hollows. The problem of tree removal is not one that can be simply solved by planting new ones. It will take them about 100 years to start forming hollows. Species can go extinct while they wait!
(Don’t let this put you off planting, of course.)
Big old Eucalyptus trees are often hollow. Despite this they have a lifespan of 300 to 500 years, and may stand for several hundred years more. There are still plenty of dead trees standing firm and tall in our paddocks, and showing a telltale ring around the trunk. They were probably killed by ringbarking around 1860.
As engineers explain to us, a pipe is almost as strong as a solid steel post.
Dropped limbs are part of the hollowing process. The stump of a dropped limb makes the best nest for all kinds of native birds and mammals.
As it drops, though, the limb isn’t so popular with humans! Most large species of Eucalypt are a dubious choice for suburbs, and have no place in any but the largest of gardens. And as plenty of drivers who use Cathedral Drive will verify, they can be dangerous when they hang over roads - especially roads where people want to drive at 100kph, so might not have time to avoid a dropped branch.
Not all Eucalypt species are widow-makers, however. If you want to plant a potentially big one near buildings or roads, you should choose one of the better-known timber species. The strength which makes them good for building also lets them keep their limbs on.
Many of Australia’s best-loved and most beautiful trees are Eucalypts of the limb-dropping kind. As the world grows ever more crowded, land use is needing to be more carefully planned. Let’s hope there’s space, in the planning, for lovely old gum trees.
(See the article posted 6 June last year for more on the value of hollows in trees.)

Monkey Rope

Parsonsia straminea
Family: APOCYNACEAE
The monkey rope vine is probably the most common vine in our district. It’s not a showy plant, but its virtue (apart from being one of our most characteristic natives) is of being a very tough green-leafed vine which would cover trellises and create shady pergolas with no fuss at all. Vines are typically rainforest plants. Many of our locals are also at home in dry rainforests. Few of them, however, are really happy to be growing in full sun, unperturbed by our district’s frosts and droughts.
This well-known old vine is a landmark at Highfields. It is in a paddock on the eastern side of the highway, just north of the Danish Flower Art shop.
Who knows how old it is - but it would certainly have been there long before white settlers appeared on the Darling Downs.
It would have begun life, as Parsonsias do, in a spot where it was lightly shaded by surrounding trees. It began to climb a tree trunk - perhaps on a long-vanished tree - using the little roots it put out at each node, and making a pretty pattern with its paired leaves.
When it got high enough to find some branches, it gave up the root-climbing habit, and began to climb by twining its stems around the branches instead.

The shiny leaves are so attractive and the plant so trouble-free and easy to grow that it should be one of our local garden staples. Monkey ropes can be found on all sorts of soils, from poorly drained clay soils and alluvial river flats to stony hillsides.
The flowers occur throughout the year. The flowers are sparse, small and inconspicuous, but have a lovely perfume. They attract butterflies, some of which also breed on the leaves.
The woody, pencil-shaped seed follicles turn brown as they ripen, and split open to release a cloud of little seeds, which float away on their little brown silk parachutes.

Strangler Figs

A strangler fig is a good choice if you have room for a big tree, and want it in a place where you already have a large but dead or dying tree - or perhaps just a large tree which you'd like to see replaced in the long term with something big, shady, and environmentally friendly - (some of our weedy camphor laurels or celtis trees, perhaps?)
Strangler figs can be planted in the ground, but grow very much faster if established higher up. In nature, they begin their lives high above frost level, usually in the fork of a living tree. As they grow, they send their roots groundwards. These roots may be invisible at first, inside the trunk of their host.
The photo at left was taken in a North Queensland rainforest, but you will see examples of the same process in our local forests.






Here is one which was interrupted by the felling of its host - but you can see that it's going to survive. It will be a very odd-shaped big tree, one day!




Assuming that the host tree remains upright while its house-guest continues to grow, it is eventually covered by the fig's roots, and dies. This may not happen before its time, however. There do seem to be some elderly host trees whose lives are extended, their weakening trunks supported in their old age by strong young figs. Meanwhile, the fig-host combination is an attractive and interesting thing, very appropriate as an ornamental feature for parks and large gardens.
Strangler figs are so strongly characteristic of our part of the world that they add an authentic touch to any assemblage of natives, particularly one with a rainforest theme.

A Hardy Local Strangler
Ficus rubiginosa
Family: MORACEAE
Known as "Scrub Figs", these are the toughest and most drought hardy of our local stranglers, happy in situations well away from the rainforests favoured by their cousins. They frequently begin life in exposed sites on an old dead trees, and are commonly seen in paddocks around Toowoomba. Many of them have been planted by farmers, who take advantage of standing dead timber to keep the young trees out of reach of browsing stock until they are large enough to provide shade for them.
Establishing stranglers is a simple matter of imitating nature, and planting them up high, out of the frost’s reach. Even where frost is not a consideration, high-planted figs always grow much faster than those planted in the soil. A small pocket of well-rotted leafmould or sawdust, and little bit of water at planting time is all they will ever need - though of course they will grow faster if they can be given more.
Some sturdy posts (such as old-fashioned house stumps, of the sort which support old-fashioned, high-set Queenslanders), can even be installed with figs planted in their tops. A hole the size of a 15cm pot is more than adequate room for them. What a clever way of getting a shady avenue of tall trees in a relatively short time.
We once recognised several local species of strangler fig, some growing on trees, others happily "strangling" rocks. They were known by various names including "Ficus platypoda" and "Ficus obliqua var. petiolaris". Botanists have now decided that these distinctions were rather artificial, and our local species are really all part of the same widespread genus, F. rubiginosa.
This comes as bit of a surprise to us, as "rubiginosa" means "rusty" - and our locals have no hint of rusty colour on their shiny green leaves. However, in the Sydney area the species does have rusty colouring on the undersides, and this is where the name was given to it - so however inappropriate it may seem, we're stuck with it.
As they grow, native figtrees fit themselves to the space available. In a crowded forest they grow tall and thin. In open, sunny spaces they develop broad, shady, umbrella-shaped canopies.


Figs are very bird-friendly trees, their dense canopies providing nesting sites, and their fruits, which can occur at any time of year, providing food for the fruit-eaters at all times of year. These were photographed at Gowrie Junction a few weeks ago.

Woodland Clematis

Clematis decipiens (previously included in Clematis microphylla)
Family: RANUNCULACEAE
I have just spent a delightful afternoon with friends, rambling over a hillside at Gowrie Junction where this plant is flowering spectacularly.
We wanted to learn how to distinguish between the male and female plants - and found it easier than we expected.








The male flowers held their heads up and looked us straight in the eye









- and were crowded in masses all over the plants.

















The female flowers were numerous, but definitely not in such crowds, on the female plants.











They hung their heads modestly, their silky tresses gleaming in the slanting sun. We could actually pick them from afar by the gleam.








This clematis, with its creamy-yellow flowers, is one of my favourite plants, and I am surprised that it’s so rarely offered for sale, and almost never seen in gardens.
It’s a relatively small climber.
A trellis about a metre square would be enough for one plant. Its woody stems never get thicker than your little finger. It is so dainty that it looks delicate, but is really one of our toughest plants, resisting our worst droughts, and frosts. (Don’t expect the same frost hardiness from the white-flowered coastal variety of this plant.)



The female plants go on to produce these lovely “old man’s beard” seedheads in summer. Males are needed for pollination, of course, so for the best long-term display a number of plants would be grown to ensure having both sexes.
This is a particularly good plant to grow on a fence, but it can also be set free in a shrubbery, where it will go almost unnoticed until it flowers.