Creating a Soak or Frog Bog
By Claudia Green
You may not be able to fit one of our amazing billabongs into your property, but there are other options for attracting wildlife to your garden and for harnessing some of all that rainfall!
A soak is a simple depression in the ground that captures water runoff from hard surfaces and allows it to slowly infiltrate the soil. When planted up with suitable plants, a soak provides a haven for wildlife, replenishes soil water and reduces runoff.
To build a soak it is best to pick a spot in your garden that is already a natural low point and where it can capture water running off from hard surfaces. Next time it rains, watch where water pools in the garden and where it runs off rapidly and potentially causes problems, such as puddles directly outside the door, water running under the house or eroding you driveway. If there is a spot where water pools naturally and it is convenient, then locating the soak here will save you a lot of hassle. Ideally, locate it where it will help capture some runoff from paths, roads or roofs (although a down pipe might deliver more water than the soak can handle during heavy rain).
Dig down about 50cm in the centre and create some gently graded “beach” areas around the banks. The soak should ideally be at least 1m in diameter but you can turn it into a more interesting shape. Make sure it is wide enough that you have enough space to place some larger rocks around the edge and even one or two in the middle.
Once you have dug your hole you can line it with geofabric to reduce weed growth and help keep the subsoil from muddying up the soak. However, this is not essential, as the base of the soak will have pebbles, rocks and plants in it anyway. If you have very sandy soil you may wish to use geofabric or another permeable liner or even line the base with clay in order to keep the water in the soak a little longer.
Now you might want to include some larger rocks around your soak. These rocks will help protect the banks against erosion, provide shelter for lizards, frogs and insects and are visually appealing. Use a range of sizes and shapes based on your budget and capacity to carry and place them on site and remember that very large rocks around a small soak will look out of proportion.
You can also use rocks and pebble in the base to create dry creek beds at the points where water actively flows into the soak. Again this will prevent erosion and will filter mud and other debris out of the runoff water before it enters the soak.
Finally, plant up your soak with suitable plants that filter the water and provide shade, shelter and food for wildlife. These plants will need to be able to cope with both wet feet AND drying out. The following list is some of our best performers for these types of environments. For more plant ideas visit your local community nursery.
Strappy leaved plants: Great for filtering runoff and preventing erosion due to their fibrous root systems.
- Dianella species
- Lomandra species esp. L. longifolia and L. confertifolia
- Poa labillardieri
- Meeboldina scariosa
- Dichondra repens
- Viola hedraceae (plant in the shade)
- Pratia pedunculata
- Callistemon species – check with your nursery as they come in many different sizes and various flower colours
- Banksia robur
- Viminaria juncaea
- Tristianopsis laurina
- Acacia cognata
- Waterhousia floribunda
Nurture your soak as you would any other part of the garden, watch it grow and watch and listen for the sites and sounds of the wildlife that will soon call your soak “home”.
It is amazing how frogs will simply appear when there is a suitable water source. Even though your soak will most likely dry out during summer, simply providing a temporary body of water still gives frogs and other animals a safe place to breed, feed and find shelter.