Which Mulch Should I Use?

There is no escaping the summer heat but with a little help from a blanket of mulch, your plants can survive and perhaps even strive. Mulch stops moisture evaporating from the soil, reducing water loss by about 60%. It also keeps the soil temperature constant and prevents weed seeds from germinating.

Every container and garden bed should have a layer of mulch that is renewed regularly. There are organic and inorganic mulches available. Organic mulches break down and add organic matter to the soil improving its structure and drainage. It also promotes earthworm and microbial activity.

Pea Straw and Lucerne Hay are organic mulches that are available by the bale and are easy to use and inexpensive. They are particularly useful for vegetable gardens and around fruit trees and last several months before breaking down. Do not be concerned if peas sprout from the straw; these can be cut and dug back into the soil adding bonus nutrients. To spread across the surface of the bed, simply break the bale of straw or hay up into biscuits and lay it out like tiles.

Sugar Cane Mulch is made from dried sugar cane leaves and tops. It breaks down easily but quickly which means you’ll need to top it up regularly. As it breaks down it encourages soil organisms which is great for vegetable gardens.

Lupin Mulch is high in nitrogen, improves the soil as it breaks down and will not blow away. It is available by the bag or can be home delivered in a large bulk bag which covers an area of about 50m². It is ideal for all garden beds including Australian natives and should be applied twice a year at a thickness of about 4cm.

Bark Based Mulches are also organic and come in various grades from fine to coarse. Medium to coarse grade bark mulches are best as they don’t absorb any moisture and allow all rainfall and irrigation to penetrate through to the soil where it is needed. Fine grade mulches tend to soak up the moisture like a sponge before it can get to the soil. Bark mulches break down very slowly and last a long time but they can draw nitrogen out of the soil so overcome this by applying an organic fertiliser to the garden bed before a 4 to 7cm layer of the bark mulch.

Compost is too fine to be effective as a mulch. Instead, use the compost as a soil conditioner by putting a layer of this underneath the layer of mulch.

Inorganic Mulches include gravel, river pebbles, scoria and even coloured rubber that don’t break down at all. These provide colour or texture to the garden whilst still reducing moisture loss from the soil. They are applied at a thickness of about 4cm and look fantastic in formal raised garden beds or on top of pots. In the long term they can begin to look messy if leaves or debris fall on to them or if planting holes are frequently dug in the area.