A short and sweet piece this week. For anyone who cares for a stretch of creek, the management challenges are often significant. As discussed in previous articles in this series, Illawarra waterways suffer from the legacy of inappropriate development, land clearing, invasive species, creek realignment, and profound disruption of First Nations People's ways of caring for Country. Plus they face the growing onslaught of climate change, with rainfall increasing in intensity as temperatures rise.
There are some simple actions that anyone can take to help to minimise the risk of problems upstream or downstream. Many of these are mentioned in Wollongong Council's Private Creeks Fact Sheet. And, apart from not putting built structures, furniture or lawn clippings in or near your creek, a key recommended action is to grow plants. Of course, it's a hard agree from me!
But the fact sheet doesn't provide any detail on what species might be suitable. And this is really important if you want maximise the potential of plants that will grow well, enjoy the local conditions, and successfully stabilise your creek banks in the least amount of time possible.
Working with local bush regenerators, community volunteers and others, Landcare Illawarra (of which I'm currently chair) has devised a list of plants that will be suitable to stabilise most waterways across the region, where erosion is not so severe or advanced that it's beyond the work of plants.
While every creek is unique in terms of its soils, pre-colonisation vegetation, current condition and other factors, there are many plants that make excellent creek stabilisers and that grow throughout the Illawarra region. Some plants, like Spiny-headed Mat-rush (Lomandra longifolia) pictured above, are well known, and are outstanding creek stabilisers, but there are dozens of others that are suitable. I'll feature just a few of them here.
A few local trees are incredible soil stabilisers and will cope with the variable conditions of dry and flood. Their larger root system means they can help hold creek banks together and also increase the capacity of soils to absorb rainfall.
One very widespread and useful small tree is the Sandpaper Fig (Ficus coronata), also known as the Creek Fig. The smallest of the indigenous fig species, this tree self-seeds all around the region and does excellent work holding together creek banks. It has the added advantage that, if a tree blows over, the fallen limbs are able to put down roots into the soil and keep the tree alive.
Some of the other native figs of the region, including Moreton Bay Fig (Ficus macrophylla) and Small-leaved Fig (Ficus obliqua) also do well alongside creeks.
In the south of the region, the River Oak (Casuarina cunninghamiana) is a magnificent large tree that grows along waterways. It is known from Marshall Mount Creek and south, and is prolific and easy to spot in the Kiama Local Government Area, where it lines creeks in Foxground, Kiama, Toolijooa and elsewhere.
Other local trees that often grow adjacent to waterways include Cheese Tree (Glochidion ferdinandi) and Lilly Pilly (Syzygium smithii), both well-known for popping up in gardens, and both local palm species, Cabbage or Dharawal Palm (Livistona australis) and Bangalow Palm (Archontophoenix cunninghamiana).
Trees are only part of the equation, though. Grasses, vines and ground covers should also be included in the mix. Beyond the ubiquitous Spiny-headed Mat-rush (Lomandra longifolia), there are plenty of other local grasses and strap-leaved plants that will do a good job stabilising creeks.
Foremost among them is the Blady Grass (Imperata cylindrica). Professional bush regenerator Wendy Midgley often recommends this grass for its dense and tough rhizomes, and for the resilience of its tall foliage, which bends without breaking in flooding conditions. It eventually spreads over large areas, and tolerates very harsh conditions.
Basket Grass (Oplismenus hirtellus and also O. imbecillis) is a common garden grass that, despite its sometimes sparse appearance, is surprisingly good at holding soil together. It establishes quickly and spreads easily, and pretty well always a good addition to riparian areas.
Lower down on creek slopes, plants that like permanently wet feet or permanent water will grow well. These include a range of sedges and rushes, most commonly seen the Common Rush (Juncus usitatus). This plant is another one that tends to find its own way to places that suit it, and from there spreads into suitable habitat. It is fairly easily available if you need to acquire some.
About the writer
Emma Rooksby is a local volunteer bush regenerator and environmental educator who helped establish the Growing Illawarra Natives website. She is passionate about protecting and restoring local biodiversity in the Illawarra region and collaborates with many groups and individuals who share that passion.