Mulch

Sheryl:  This article came about because George went to visit Chester Dott from Forbidden Fruit Nursery and noticed that he was using Tea Tree as a mulch to stop weeds from forming on top of his pots as he is organic.

Mulch is an effective and protective covering which when placed around plants can prevent the evaporation of moisture, the freezing of roots and the growth of weeds. There are many benefits of using mulch in and around the garden, these include:

• deterring weeds
• decreasing pest invasion
• absorbing water and decreasing evaporation
• improving sandy and clay soils by adding organic matter
• stopping erosion
• insulating the soil, by keeping it cooler in summer and warmer in winter
• preventing soil compaction
• improving the look of your garden!

There are a few things to consider when choosing your mulch:
Function – do you need it to improve the soil and structure, conserve water, or inhibit weed growth?
How long it will last, the ease of application, availability and cost
Appearance – would you like the mulch to be decorative or to blend in?

There are two types of mulches: organic and inorganic.
Organic mulches are made of natural substances such as lucerne, wood chips, leaves or grass clippings. They decompose over time and need to be replaced.
Inorganic mulches can be made of materials such as gravel and pebbles.
They do not add nutrients to the garden or break down.

Organic mulches:
Lucerne

Excellent for improving soil, available in bales, easy to transport, carry and spread and can last for about 3-4 months. However lucerne can contain weed seeds that may germinate.

Sugar cane mulch
It is weed free but can form a water-resistant mat on the top, so ensure that the ground is well watered before application. It lasts 3-4 months, is easy to spread but it is advisable to wear a facemask to avoid breathing in the dust.

Grass Clippings
The best use for grass clippings is to leave them on the lawn. If you do want to use them as mulch, let them dry out first or compost them. They will decompose rapidly, adding nutrients back into the soil. A five centimetre layer will provide weed control if they are not full of weed seeds.

Straw
Decomposes rapidly, so you will have to replenish it often to keep the weeds down.
Straw will improve the soil as it decays.

Wood chips and pine bark

These are recycled products from plantation timbers, green waste, and post consumer wood waste. They do not add any nutrients to the soil and break down slowly. A large wood chip can last for up to two years.
 

Tea tree mulch   
Forms a closely woven but highly absorbent mat that retains soil moisture and inhibits weed growth and is weed free. A 75mm layer can last for up to 12 months.

Leaves
A 50mm-75mm layer of leaves is a great weed suppressant.
Leaves should be shredded, using a shredder or your lawn mower.
They will improve the soil as they decompose.

Other organic mulches include pea straw, compost, manure and mushroom compost.

Inorganic mulches:

Pebbles and crushed stone 
These come in all shapes, colours and sizes. A 25mm layer of small rocks will provide good weed control.
Do not use around acid-loving plants as they may increase alkalinity in the soil, these materials can reflect the sun and create a hot environment during summer.

Recycled products
There are many recycled products now available including recycled concrete, slate, plastics and coloured road base

Mulch Mat 
This is made from woven fabric. It is available in various lengths and widths.
It allows water and air to circulate and is effective in controlling most weeds

Do’s
Before you apply mulch give your selected area a good weed and water well.
It also helps to break up the soil.
Apply the mulch in a thick layer, about 75mm

Don’ts
Mulch right up to the trunks of plants.
Use hay for mulch as it contains too many weed seeds. The best time to mulch new plants is right after you plant them. Around established plants mulch is best applied in early spring. Remember to replenish your garden bed with mulch from time to time, as it breaks down.

Troubleshooting
Nitrogen drawdown
This is the loss of nitrogen from the soil, occurring when mulch of high carbon/low nitrogen content is used, such as woodchip. This can cause yellowing of the leaves and poor growth. Using an organic mulch will help prevent this. Ensuring your soil is well prepared before applying your mulch will also help your plants to thrive.

Stem rot
This can occur when mulch is touching the stem or trunk of your plants.

Mulch can sometimes dry and repel water if it is in small particles.
Simply rake it to break the surface, then water it

Grow your own mulch
By growing a ground cover such as Native Violet, Kidney Weed, Blue Flax Lily or Ivy-leafed Violet you can cover the soil and this will act as a mulch.

 

Sourced from: 
www.camden.nsw.gov.au/files/environment/mulchlr.pdf
Date sourced: 
Feb 2008