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Close-up of someone wearing boots digging into soil with a garden fork
The key to a bountiful garden is a good foundation. Your plants will find it difficult to survive in waterlogged clay soil. Get the most out of your garden with our tips to healthy soil.

Ground breaking

Heavy, clay-based soils are hard work. They’re difficult to dig and even if you manage to break through and dig a hole or trench for planting, it’s not the ideal growing environment for most plants. Clay holds onto nutrients and water well, but too much clay leads to drainage issues; in the long run, plants are unlikely to survive.

The good news is that you can improve the soil, but it is not an overnight fix. The addition of soil conditioners and amendments like organic matter and gypsum will help to break up the clay and improve the overall soil structure.

Clay check

How do you know if you have clay soil? Aside from being difficult to dig, when wet, clay is sticky, pliable and takes a long time to dry out. Medium to heavy clay soils will take a long time to drain, too. If this is the case for your soil, you will need to improve the soil prior to planting.

Close-up of someone wearing gumboots digging a hole with a spade

Save my soil

Before taking action, try doing a simple test to see what additives will be beneficial for your soil. Take a small sample of dry soil and add it to a jar of clean water. Do not shake it, but simply observe. If the water becomes milky and cloudy, the soil will respond well to the addition of gypsum, a well-known clay breaker. If it’s not cloudy, it’s unlikely gypsum will help. 

Apply organic matter like compost, blood and bone, and aged manures liberally to the area. Add gypsum if needed, following the instructions on the back of the pack to understand how much is needed. Gypsum is available in both powdered or liquid form, with the liquid being more fast-acting than powder. Dig all the additives well into the soil. Repeat applications may be required to further loosen the soil.

If the soil is too difficult to dig, layer compost and manures over the area and cover with an organic mulch like sugar cane or pea straw. Wet the mulch and allow it to break down over the next few weeks. If it’s workable, dig it all in, but if not, allow the organic matter to further break down.

To check if plants are ready for planting, dig a hole at least 40cm deep, fill with water and note how long it takes to drain. If the water drains away after a couple of hours, it’s moderately well-drained. However, if it’s still sitting there after a day, you have more work to do.

A person watering a garden bed using a watering can

 

Maintaining the soil

Once plants are in, it’s ideal to continue to add organic matter and gypsum 2–3 times throughout the year. A healthy soil ensures plants are happy and less prone to pests and diseases.

Clay-tolerant plants

There are plants that are more tolerant of growing in clay soils, provided they’re well-drained. In fact, once established, they will thrive too. 

  • Callistemon ‘King’s Park Special’ or ‘Little John’
  • Lomandra longifolia and cvs
  • Myoporum parvifolium and cvs
  • Dianella 
  • Pennisetum
  • Canna lillies
  • Nandina

While you’re tending to your soil …

Follow our guide to testing and adjusting your soil pH, essential to growing healthy plants.

 

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Health & Safety

Please make sure you use all equipment appropriately and safely when following the advice in these D.I.Y. videos. You need to be familiar with how to use equipment safely and follow the instructions that came with the equipment. If you are unsure, you may feel it is safest to consult an expert, such as the manufacturer or an expert Bunnings Team Member.

Grave health hazards are linked to asbestos, which may be in homes built up to 1990. Health hazards may result from exposure to lead-based paints in older materials and copper chromium arsenic (CCA) treated timber. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer. You can also use a simple test kit from Bunnings to indicate the presence of lead-based paint.