Contributed by Ethan Mimnaugh, Mooloolah Landcare Nursery
WE often lament sandy, waterlogged soils. They are hard to grow a nice lawn on, and often these kinds of soils are by the coast, and so the salty air affects a lot of the pretty plants we are used to growing in gardens.
Often times, a tropical approach is taken in these soils, but in our subtropical climate, this often means irrigating during dry times or seeing a lush garden wilt and dry up. The answer, as savy readers may have realised, is to embrace these soils, which give rise to an ecosystem called the Wallum.
Wallum is an indigenous name for the Wallum Banksia (Banksia aemula) which grows as one of the dominant species in parts of the wallum. This is a gnarly looking Banksia with huge green-yellow flower structures which attract birds, insects, and mammals. The plant is said to be important to some indigenous people because of that same flower, people also enjoying the sweet nectar.
There are other Banksias which are also found in the wallum, or in nearby, drier heath, such as the Dwarf Banksia (Banksia oblongifolia), or the Old Man Banksia (Banksia serrata). The later of these is often confused with Banksia aemula, but is a larger tree and has a very slightly different flower.
Due to its mineral and hydrological surroundings, wallum soils can be nutrient poor. This means that many of the plants are much smaller than closely related species that occur elsewhere. One example is the Wallum Bottlebrush (Melaleuca pachyphylla) which has 2 varieties, red flowering and green flowering, and grows under 2m tall. Another is a Thyme Honey Myrtle (Melaleuca thymifolia) which is an even smaller, denser shrub with purple flowers.
Both of these plants are very closely related to the Broad Leaf Paperbark (Melaleuca quinquenervia) which gets up to 25m in swamps, watercourses, and floodplains! The ecosystem which develops when plants are small, is an ecosystem adapted to high levels of light. This means that brightly coloured flowers and fruits are the best way to attract pollinators and seed dispersers.
In the wallum there are huge varieties of pea flowers, yellow, purple, even some white. These nitrogen fixers can boost soil fertility when they die, helping following generations to grow more easily.
Other commonly seen types of flowers are the Ericaceae family, the Heath family. This group of plants often have small white flowers which are followed by berries of various kinds which provide food, while their shrubby, stiff leaves provide incredible habitat for them. They are related to the Blueberry plant, and equally are tolerant of acidic, and otherwise, poor soils.
Wallum Grass Trees (Xanthorea fulva) are a world famous site, and their large flower spikes are an amazing feature in poor soils. They grow from tubestock quite well if they are protected from being stood on while they are young. They flower well after being burnt, and when done carefully, this can promote the growth of the plant for following years as well.