Mulch and how to use it

This protective layer is a gardener’s secret weapon to fighting weeds, retaining moisture and having generally tidier flower beds and vegie patches.

Bunnings magazine, February 2021

What is mulch?

Mulch is one of the gardener’s most valuable tools. It blocks weeds from resprouting, keeps roots cool in the heat of summer and provides a clean, organised aesthetic that makes it easier to navigate around your plants.

“Mulch is a bit like a protective blanket,” says horticulturalist Chloe Thomson of @beantheredugthat, and host of Bunnings podcast Staying Grounded. “It helps reduce evaporation, suppresses weeds and, as it breaks down, adds organic matter and nutrients to the soil,” she explains.

When should you mulch?

Mulch at any time but, for best results, apply it at the start of the growing season, preferably when the ground is damp.

“In the vegie garden, work the old mulch into the soil and then replace with fresh organic mulch once you have planted,” says Chloe.

In the rest of your garden, organic mulches should be reapplied every year to keep them at a depth of 3-4cm, while inorganic mulches, like pebbles, will only need topping up every few years. 

How much do I need

More mulch is not always better – if applied too thickly, it can prevent rain and irrigation reaching the plant roots. The amount needed varies based on the product, but for bark mulches, aim for around 3-4cm.

“Straw can be slightly thicker – up to 7cm, as it is light and fluffy, and weeds can easily push through thin layers,” says Chloe. Grass clippings and leaf mould can gradually be built up to a 5cm layer – if you have excess, split it with the compost bin.

Organic mulch

Natural materials such as pea straw, sugar cane, pine bark, seed-free grass clippings and leaf mould make great mulches, as they break down and help improve soil structure, according to TV gardening expert and Richgro ambassador Charlie Albone. “But keep it away from stems and trunks to avoid stem rot – instead, create a moat around newly established plants to help trap water and direct it to the root zone,” he adds.

Leaves: These need to be shredded first, or composted. If left whole, they can clump and form impenetrable mats that can suffocate the soil. An easy way to shred leaves is to mow over them. They will then break down over the season, providing nutrients to your garden in the process. The downside: if you live in a windy area, they can blow away.

Wood waste/bark: Mulches made from untreated wood waste or bark break down slowly and won’t blow away. However, woodchips are low in nitrogen, which can cause a temporary deficiency in soil. Add a conditioner, such as blood and bone, to soil before applying wood-based mulch.

Sugar cane mulch: This breaks down easily over the year to give your garden the benefit of added nutrients, but it’s not great for windy areas. Imported sugar cane mulch is not available in Western Australia, as it may contain the seeds of prohibited weeds.

Grass clippings: An excellent, free source of mulch. They’re also great for boosting and conserving soil moisture.

Pine needles: These are good for acid-loving plants and a great mulch for strawberries – of course, you’ll need access to pine trees to source a decent supply for your garden..

Coir mulch: A decorative mulch, this is light and quite easy to transport, and also typically contains fertiliser.

How to use mulch

Inorganic mulch

Stone/gravel: This is an aesthetically pleasing option, but better used to create paths through a landscape, over pots or areas where a more designer look is desired. “It adds nothing to the soil, so you will need to address the lack of organic matter by adding extra compost to the soil,” says Charlie.

Landscape fabric/weedmat: Weedmat is a porous material that suppresses weeds. While weeds can sometimes grow through the upper layers of cheaper fabrics, the more expensive products may last up to five years. It’s a little bit unattractive on its own, but can be covered with mulch so it’s less visible.

How to use mulch

More information

Learn how to install weed matting using our step-by-step guide.


Photo credit: Getty Images, Gap Photos/Perry Mastrovito
Cherry Plant

Planting & Growing How to plant and grow a cherry tree Sweet or sour, cherries are a popular summer treat around the world. Lovely and narrow, the cherry tree is suited to areas with cold winters, creating a stunning display of blossom in spring followed by the much-loved fruit.

plant pots 03:15

Planting & Growing How to grow and care for indoor plants For people unable to garden outdoors, growing indoor plants allows them to indulge in a hobby that gives great pleasure.

bird of paradise plant

Planting & Growing How to grow and prune a bird of paradise Hardy, easy to grow and architecturally dramatic with some of the most stunning and bizarre flowers you will ever see—that’s the awesome bird of paradise.

Apple Tree

Planting & Growing How to grow and prune an apple tree Nothing beats the crunch and taste of a fresh apple. So why not grow your own? An apple tree can be so much more than just a fruit tree.


Planting & Growing How to plant grow and harvest basil An attractive garden plant that’s easy to grow and is an essential ingredient in a multitude of dishes. That’s basil!


Planting & Growing How to plant grow and prune bougainvillea If you’re looking for a plant with vibrant colours to bring a tropical look to your garden, then you can’t go past bougainvillea.

How to design a herb garden 01:23

Planting & Growing How to design a herb garden Turn your back or front yard into a beautiful, productive space by creating an edible garden that looks good and will tastes even better. For this project, we’re grouping our herbs into three pots – one for tea, one for smoothies and one for cocktai...

Choose a sunny spot and watch 01:40

Planting & Growing How to grow strawberries You’ll love the taste of home-grown strawberries. It’s a great activity the whole family will have fun doing.

Health & Safety

Please make sure you use all equipment appropriately and safely when following the advice in these D.I.Y. videos. You need to be familiar with how to use equipment safely and follow the instructions that came with the equipment. If you are unsure, you may feel it is safest to consult an expert, such as the manufacturer or an expert Bunnings Team Member.

Grave health hazards are linked to asbestos, which may be in homes built up to 1990. Health hazards may result from exposure to lead-based paints in older materials and copper chromium arsenic (CCA) treated timber. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer or visit our Health & Safety page. You can also use a simple test kit from Bunnings to indicate the presence of lead-based paint.
Top of the content