This is a guest article by Wendy Cook.
It’s cold, the middle of winter. On some mornings the ground is white, puddles are frozen with patterns of angular lines and leaves have a covering of tiny icicles. On other days it feels as if the wind is coming straight off the Southern Ocean, but in the bush, the hakeas have opened their curly white flowers. On the roadside, the first clematis blooms have appeared with long pale green petals and a tuft of stamens in the centre of each flower. The tree violets have branches laden with lime-green buds, waiting until it is time to open their tiny, creamy-yellow, bell-shaped flowers and release their perfume. By the creek, the silver wattles are preparing. Their grey branches end in white twigs with feathery grey-green leaves and stalks of tiny yellow balls; not open yet, but they will be soon. For me, wattle flowers are a sign that spring is coming.
Living close to the Brisbane Ranges, there are plenty of wattle species to be seen flowering here at this time of year. Some of the species found in the Ranges are widespread around Victoria, whilst a couple are less common in other areas of the state. One wattle already beginning to flower is the golden wattle (Acacia pycnantha). With its bright gold clusters against green leaves, it is Australia’s floral emblem. However, wattle leaves and flowers aren’t always what they seem.
The feathery leaves of trees such as the silver and black wattles are true leaves. Young wattle seedlings have small feathery leaves, but soon begin to grow very different looking leaves. These later leaves are not truly leaves. They are flattened stems called phyllodes. They can be shaped like gum leaves, as in golden wattle, or be more sickle-shaped, round, triangular, needle-like or thorns. They still fulfil a leaf’s purpose of making food from sunlight, but they are tougher, allowing wattles to live in arid places. Having very small phyllodes or just thorns means the plant loses less water, but it also makes less food, so it will grow slowly. As well as phyllodes, some wattles have thorns to deter browsing animals, or contain chemicals which taste bitter. Wattle leaves and phyllodes have glands which secrete sugary compounds to attract ants. The ants protect the wattle from other insects, some ringbarking branches of neighbouring trees to stop them competing with their home tree.
Most wattles are bushes or trees. One of our more unusual locals is the thin-leaf wattle (Acacia aculeatissima). It grows as a mat of tough stalks and short needle leaves, rarely reaching more than a few centimetres high. When it flowers in spring, it looks like someone has sprinkled a handful of tiny yellow pom-poms on the ground.
The flowers of wattles are also not quite what they seem. Each round yellow ball is made up of many tiny flowers. The fluff that we see is the stamens, tipped with anthers laden with pollen. The petals are so small that we don’t notice them. Some wattles have their flowers arranged in a cylindrical spike and their colours vary from pale creamy yellow to almost orange. The flowers are strongly scented, but do not produce nectar. Instead, insects eat some pollen, become covered in more, and spread it to other flowers. Birds chasing the insects may also act as pollinators. Wattle seeds with tough outer coats grow in pods. The pods split down the side to release the seeds, but may remain, brown and curly, on the plant long after they are empty.
Wattles can grow in poor soils and are often among the first plants to grow in a disturbed area. They are assisted by bacteria called Rhizobium which invade their roots. The infection causes a lump or nodule on the root, in which the bacteria live. The bacteria can take nitrogen, which is necessary for plant growth, from pockets of air in the soil. The wattle uses the nitrogen and in return, provides the bacteria with sugars to make energy.
In the Brisbane Ranges, we have over 15 species of wattle, flowering at different times of the year. The latest is Mitchell’s wattle, a small bush displaying pale yellow flowers in the heat of summer. For now, while it’s still cold, you can go outside and enjoy the wattles and other flowers announcing the beginning of spring.
Wendy Cook lives on a farm west of Melbourne with her husband and two teenagers. She loves watching the nature she sees around her every day and writing about it. She is a volunteer with Fungimap and at her local primary school where she hopes to instil a love of nature and reading in the children.
Banner image courtesy of Owen Cook.