Mulch and compost

Ensuring a water efficient garden

Implementing simple measures such as mulching and composting makes your garden more water efficient and helps keep it green even during times of drought.


Mulch can reduce evaporation from soil by up to 70%. Mulch is like a blanket on the soil. Not only do mulches conserve water and mean there's less need to irrigate, they also keep the soil a consistent temperature, reduce weed growth and, over time, improve the soil structure and health of plants.

Mulch is an essential component of maintaining a water efficient garden. The basic rule is any mulch is better than no mulch. Kevin Walsh, author of Waterwise Gardening, (Reed New Holland, Third Edition 2004), describes three kinds of mulch:

  • Coarse mulch, like pinebark, pebbles and even recycled concrete and bricks makes a long lasting mulch and is excellent for preventing weeds. It's also very good for keeping the soil cool, particularly if it is lightly coloured. This mulch won’t improve the soil much and in the short term will take nitrogen out of the soil. This can be compensated for by spreading some nitrogen-rich fertiliser on the soil before spreading the mulch. This sort of mulch can be 50-75mm (3 inches) deep.
  • Medium mulch, like pine bark or wood chips is also excellent for reducing weeds. This sort of mulch is usually laid 25-50mm (2 inches) deep. One danger with mulches is watering too often, bringing roots up to the surface of the soil under the mulch. If the mulch goes or the surface soil dries out, when the roots are too shallow, the plants die. The solution is less frequent watering.
  • Fine mulch like sawdust and euca can stop water getting into the soil, so don’t make it too thick - about 25mm (1 inch) deep - and top it up each year when the ground is starting to dry out. Pea straw, cow and horse manure and compost make excellent mulches because they improve the soil and attract worms.

Mulching your garden



Soil is a living thing, and compost is a great way to keep it alive.  Soil that drains easily, so it doesn’t get waterlogged, and holds enough water to feed the plants, is perfect for your garden - and compost will help with both these things.

Without good soil, it won’t matter how much water you put on the garden, it still won’t do well. Compost can easily be made at home or you can check out local suppliers for recycled green waste mulches and compost.

Discover ways to save water in other areas of your garden:


When to water?


How much to water?


Rainwater tanks