How To Mulch Your Garden With Organic Mulch

Mulching with organic mulch like wood chip mulch is one of the best ways to grow and maintain a lush, healthy garden. Done well, mulching your landscape with an organic mulch helps improve the nutrients in your soil and encourages growth.

Our guide shows you how to mulch your garden, explores the types of mulching materials available, and offers mulching tips and tricks to enhance your landscape. Here’s everything you need to know about mulching your garden.

Types of Mulching Materials: Organic Mulch Options

There are many different mulches, both organic and inorganic.

What is organic mulch? Organic mulch may include tree bark, leaves, grass clippings and straw. These natural materials enrich the soil with nutrients as they decompose, but will eventually need topping up.

In contrast, inorganic mulches like gravel, pebbles, black plastic, landscape fabrics and old newspaper are long-lasting, but do not contribute directly to the health and quality of the soil.

Arborist wood chips

Composed of a unique mix of bark, wood, and leaves, arborist wood chips are by the best mulching material overall.

Pros

Nutrient-rich: Because of its composition of bark, wood and leaves, arborist wood chips are ideal for enriching nutrient-poor soil. Arborist wood chips contain a variety of complex natural compounds and nutrients to help support the microbes that keep your soil healthy and aerated.
Nitrogen-rich: While normal woodchip* can deplete nitrogen in the soil, arborist wood chip helps fix nitrogen deficiencies.
Supports a biologically diverse soil community: The bark, wood and leaves found in arborist wood chip come in a diversity of sizes with varying decomposition rates. This allows your soil to support a greater diversity of microbes, insects, earthworms and beneficial organisms that bolster the health of your plants.
Attractive: Arborist wood chips give your property a polished, natural look with a consistent coloured and textured surface across the garden.
Excellent moisture retention: Arborist wood chips keep your soil moist, reduce water evaporation from your soil’s surface by up to 60 per cent, and decrease the need for frequent watering. It increases water percolation into the soil profile.
Weed control: A thin 4–6cm layer of wood chips provides excellent weed control.
Soil protection: Arborist wood chips help improve your soil structure, reducing erosion and soil movement from garden beds.
Keeps soil temperature well-balanced: Wood chips help moderate soil temperature throughout the year in winter and summer.

Cons

Risk of collar rot: Wood chips should not be allowed to touch a tree’s trunk or root base.

*If you choose to use normal wood chips instead of arborist wood chips, we recommend applying composted manure as an underlayer to help your soil maintain a healthy ratio of carbon to nitrogen.

Grass clippings

Pros

Ideal for lawns: Grass clippings provide the ideal nutrients to grow a lush lawn.
Soil insulation: Clippings can help insulate your soil in cool weather and keep it cool and moist in hot weather.
Soil nutrition: Grass clippings provides nutrients for beneficial microbes in the soil.
Weed control: Use a 5 cm to 10 cm barrier to stifle weeds.
Affordable: Grass clippings are one of the most cost-effective mulches as they can be sourced from your own backyard.

Cons

Must be pesticide-free: If your grass has been treated with herbicides, fungicides or chemical fertilisers, the clippings can transfer these chemicals into your soil.
Must be dry and cool: Grass clippings must dry and cool off before use as mulch.
May damage roots: The heat generated by straw decomposing may potentially damage plant roots.
May impeach water percolation: When wet, grass clippings can mat together, causing water and rainfall to run off.

Straw

Pros

Inexpensive: Straw is affordable.
Ideal for vegetable gardens: While not ideal for providing nutrients to trees, flowers or shrubs in your backyard, straw is perfect for vegetable gardens.
Weed control: Despite its light texture, straw helps suppress weeds.
Water percolation: Assists slow overland water flows to penetrate the soil profile.

Cons

Quick decomposition: Straw decomposes quickly. Unlike arborist chips, which give a slow, long-lasting release of nutrients, straw is useful only in the short-term.
Can be unattractive: Straw may become wet, matted and mouldy.
May spread weeds: Since straw may contain weed seeds, using straw as mulch can inadvertently encourage weed growth.

Best Mulch To Stop Weeds

The best mulches to stop weeds include arborist wood chips, tree mulch or bark mulch, compost, leaves, straw or grass clippings, or sawdust.

Best Mulch For Native Plants

Wood chip mulch, especially recycled bark, eucalyptus mulch and pine bark mulch, is the best mulch for natives, promoting microorganism activity and enhancing nutrients in the soil. As organic mulch decomposes, it releases nutrients, including nitrogen, into the soil to bolster the health of your native plants.

According to Arboriculture Australia, arborist wood chips provide superior water penetration, stop weed growth and stimulate microorganism activity. It also retains moisture and moderates the soil’s temperature better than most other mulches — making it ideal for supporting the health of native trees, shrubs and flowers. For best results, cover your soil with a low potassium fertiliser before laying down your wood chip mulch for native plants.

Best Mulch For Flower Beds

For flower beds, go for a simple wood chip mulch made from recycled branches and trees. For best results, choose a medium texture. Mulch that is milled too finely can become compacted and hold too much moisture, which evaporates and never finds its way to feed the plants. In contrast, coarse mulch is much more porous and often won’t hold enough water. Medium size bark mulch is your best bet.

Mulching Tips and Tricks

How Deep Should Mulch Be Around Trees?

Generally, we recommend applying approximately a 75-100 millimetre layer of mulch to insulate your soil, retain moisture and suppress weeds.

However, the ideal depth for your mulch ultimately depends on which type of mulch you use:

Coarse or heavy mulches: 20-60 millimetres deep
Fine or light mulches: 50-70 millimetres deep

How Should I Apply Mulch Around Trees?

Before laying your mulch, make sure every weed in the area has been uprooted. Remove any grass within a 90 to 300-centimetre radius, depending on the size of your tree or shrub, and spread your organic mulch inside this circle.

Spread your mulch evenly and leave a little gap around the circumference of your tree or shrub so the mulch does not directly touch the bark, to ward against collar rot. Avoid laying thick layers of organic mulch because this can prevent your plants from receiving enough water and oxygen, negatively impact your plants and erode your soil’s pH.

Disposing of Old Mulch – How To Remove Mulch From Yard

Each year, it’s best to remove the old mulch before you till the soil and top up with a new layer. Simply applying a new layer on top without removing the old layer can starve your plants of nutrients, cause rot and even smother your plants, resulting in plant death.

To make removing old mulch easier, rake the mulch and leaves to your garden bed edge, scoop it out with a shovel and mulch fork, heap it into a wheelbarrow, and take it to your compost pile. Apply a fertiliser before layering your organic mulch on top to add extra nitrogen to your soil.

How To Keep Mulch From Washing Away On A Slope

The best way to contain mulch in your garden beds is to edge it with a high, rigid barrier, such as landscape edging. Edging materials may include timber, metal, plastic or stone. Heavier, coarse mulches will tend to stay in place better than fine mulches during heavy rain.

When To Apply Mulch

Adding organic mulch to your garden is an excellent idea any time of the year since it helps your garden retain water, restricts the growth of weeds and adds valuable nutrients to your soil. However, in Australia, the best possible times to mulch are early spring and early to mid-summer. Always thoroughly rid your garden of weeds before mulching.

What Kind Of Mulch Lasts The Longest?

Coarse arborist mulches will last longer than smaller bark mulches. If you want your mulch to decompose slowly, choose chunky bark-type mulches over finely shredded wood.

Does Mulch Stop Weeds?

Mulch is a very effective prevention method against weeds. A layer of mulch acts as a natural weed barrier by blocking weeds’ access to sunlight, suppressing their ability to grow and germinate.

How To Make Mulch For Your Garden

If you’re looking for the best garden mulch in Australia, you can’t go wrong with arborist wood chips, combined with a nitrogen-rich fertiliser. Arbor Operations deliver eco-friendly, organic mulches direct to your door, to help keep your trees and garden healthy. As certified arborists, we can even provide advice on how often to mulch your garden or how much mulch to order, based on the specific needs and size of your property.

Interested in beginning a garden from scratch? Here’s more advice on starting a garden.

To find out more about our tree mulching services or to get in touch with us about a project, please call 1800 652 862 or inquire through our contact form.