This is a guest post by Mackenzie Kwak.
Few Melbournians out on a spring stroll through the forest would notice, let alone recognise the humble sundews growing beneath their feet. Sundews are diminutive plants, with the largest species rarely attaining a height much above your knee and the smallest growing no larger than a five-cent piece. Yet, they are some of the most spectacular and beautiful flora to call Melbourne home.
This time of year, as the chilly winds of winter give way to the warm scented breezes of spring, sundews begin their annual cycle of feeding and flowering. They are some of the few plants growing in our forests which can proudly claim the title of being carnivorous. They have developed the ability to attract, snare and digest little animals to sustain their growth. The capacity to feed on animals has allowed sundews, or the genus Drosera as botanists know them, to spread across the globe and fascinate those who have taken the time to notice them. The famous naturalist Charles Darwin was so enraptured with these plants that he once said ‘I care more about Drosera than the origin of all the species in the world’.
The sundews are a massive genus of plants containing almost 200 species worldwide, with new members being regularly discovered. They can be found from the icy peat bogs of the Arctic to streamy jungles of Southeast Asia and even the bone dry deserts of central Australia. However, Australia is the global ‘hot-spot’ for sundews and it is believed that the genus first evolved here. Today, more than 100 species can be found across our nation. While Western Australia has the vast majority of species, Victoria has 11. These are a diverse group which can be found growing across the state, from costal swamps to dry forests to alpine bogs. This diversity of habitats has resulted in a great range of varieties, such as tall-climbing forms and small, rosette-forming species.
Due to the diverse array of species and the habitats that they occupy in Victoria, our sundews have developed a complex assortment of life cycles. The most common life cycle is that of the tuberous sundews. These are species most commonly found in dry forest and arid areas, which are dry and hot in the summer and damp in the winter. The tuberous sundews lie dormant in a small tuber a few centimetres below the soil surface during the hot summer to avoid fire and desiccation from the heat. From early winter to spring, they burst forth from the earth and enjoy the wet season when the temperature is mild, the insects plentiful and the soil perpetually moist. Another similar group represented only by Drosera glanduligera in Victoria is the annuals sundews, which grow at the same time as the tuberous species. However, instead of retreating into their tuber in the hot summer, they instead survive as seeds. The final group of Victorian sundews are those that lay dormant in the winter and emerge in the warm summer. Some species, such as Drosera binate and Drosera spatulata occupy swamps and bogs which often remain wet thorough the summer, allowing them to survive the high temperatures. However, the alpine sundew Drosera arcturi lives in this way because its habitat is inundated by deep snow in the winter, meaning summer is the only period when temperatures are high enough to allow the plants to grow and flower.
Complex behaviour is not the only interesting feature of the sundew though. Nestled amongst the leaves of some of the native species growing around Melbourne lurk tiny, six-legged robbers. Much like the relationship between anemones and clown fish in the sea, sundews have their own little symbiotic associates: sundew bugs of the genus Setocoris. Sundew bugs are beautifully coloured animals, with the species commonly found around Melbourne commonly adorned with a rainbow of different shades. Despite their vivid appearance though, they are no larger than a pea. The relationship between the insect and the plant is believed to be somewhat more sinister than that of the anemones and clown fish. The sundew bug not only uses the plant for shelter, but also steels its prey. Although outwardly this may appear detrimental to the plant, some researchers believe that the plant derives nutrients from the faeces of the bug, which digests the prey and leaves nutrient-rich waste on the leaves for the plant to use.
Perhaps now you have your heart set on going out and searching for these fascinating little plants (and their insect associated) for yourself. Please remember though, that plants in reserves, state and national parks are protected and cannot be collected. Plants collected in the wild also rarely survive transplant. However, some suppliers and nurseries around Melbourne specialise in carnivorous plants, including native sundews. These can be inexpensive and transform into spectacular pot plants growing on a sunny porch, provided they are kept permanently damp. Sundews can be rewarding plants to grow and will flourish once you get the conditions right.
For more information, visit the website of the Victorian Carnivorous Plant Society.