What to use as a mulch?

What to use as a mulch?

Its been a long hot dry summer in the southern parts of Australia and the garden is really starting to feel it.   Adding some mulch to your patch can not only help with conserving precious moisture in the soil,  it has a range of other great benefits as well. 

Mulching performs a variety of functions in the garden:

  • Reduces moisture loss from the soil surface, thus aiding plant growth, and reducing the need to water. It also lessens the chance of the soil surface drying out and cracking.
  • Suppresses weed growth, which reduces competition for water and nutrients, and decreases the amount of ‘weeding time’ the gardener has to put into maintenance.
  • Many types of mulch add nutrients to the soil when broken down, and improve soil structure.
  • Mulching also reduces run-off and soil movement from garden beds.

 Mulch typesGawler Landscaping Ground Cover Mulch

As organic mulches breakdown they help improve the soil structure and add nutrients to the soil. Inorganic mulches such as pebbles, have no soil improving qualities and may have a negative effect on soil health.

Plants with low nutrient requirements, such as many native plants, often benefit from inorganic mulches. Thick woody mulches without leaves are also perfect for these types of plants as they last longer before breaking down and they release very little nutrients.

Very fine mulches are to be avoided as they can compact and not allow water to penetrate to the soil beneath. Their fineness also means they are capable of holding a lot of water, once again preventing it from infiltrating the soil beneath.

A good organic mulch is one that is a mix of fine and coarse particles.

Pea straw (pictured at top) is an excellent mulch because it is high in nitrogen, but it can also be too expensive to use as a general mulch. This is best used on areas where the high nutrient content can be utilised best, like the vegetable garden.

SGA also recommends avoiding mulches that have been harvested from old growth forests. Please ask your supplier for mulch that is only from plantation grown timber.

How to Mulch

Take these few steps before laying your mulch down to ensure success.

  1. Remove or poison weeds (then wait for a fortnight after using poison)
  2. Moisten the soil thoroughly. Ensure that the water you apply is penetrating .
  3. If the water is running off the surface, fork through some compost to aid with the water retention.
  4. If you are planting into the soil, add some water saving crystals into the planting hole.
  5. If you are using bark-based mulches, you might consider sprinkling some blood and bone over the soil. This extra nitrogen will compensate for any nitrogen being taken up by the gradual decomposition of the mulch.
  6. Lay your mulch thickly (7-8cm deep), keeping the area directly around plants free of mulch.
  7. Lastly sprinkle soil wetting agents over the surface. This will ensure that any watering doesn’t run off the surface of the mulch.

Following these steps will mean you have mulched well.

How often?

Over time organic mulches break down, contributing beneficially to soil structure. Fine mulches will break down quicker than more coarse materials and so will need topping up more often. A yearly top up is usually enough.

The length of time that it takes for a mulch to break down determines how rapidly the plants will be able to access the nutrients in the mulch. Some mulches as they break down may actually take nutrients away from the soil, this effect is only shot-term but in these instances it may be necessary to add manure or blood and bone prior to mulching.


Thanks to http://www.sgaonline.org.au/meaningful-mulching/ for this great article.


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