Mulch does three jobs better than any single garden product. It holds soil moisture, suppresses weeds and stabilises root zone temperature. Done right, it cuts watering by half and replaces hours of weeding.
Most gardeners under-mulch. A thin scatter does almost nothing. The right depth, the right material and an annual top-up makes the difference visible across the whole garden.
What mulch does
Soil moisture lasts twice as long under mulch. Weed seeds don't germinate without light, so a deep layer suppresses 80-90% of weeds. Root zone temperatures stay cooler in summer and warmer in winter, keeping the tree comfortable.
Mulch also breaks down slowly, feeding soil microbes and adding organic matter without the need for separate compost.
How deep is right
Most trees prefer 7-10cm of mulch. Moisture-loving species like Magnolia and Waterhousea appreciate the upper end. Mediterranean species like Olive prefer lighter mulching, 3-5cm, with coarser material like gravel or coarse bark.
Keep mulch clear of the trunk. Leave a 5-10cm bare ring around the trunk for a healthy collar.
What to use
Aged woodchip or hardwood bark is the go-to for most species. Pine bark suits acidic-loving plants like Camellia and Banksia. Coarse gravel suits Mediterranean species. Choose aged chip over fresh, since aged chip releases nutrients steadily as it breaks down.
Use coarse organic mulch as your main layer. Fine compost works best mixed in or used as a thin enrichment under coarser mulch.
When to mulch
Annual top-up in early spring. The first heavy layer goes on at planting. Top up to 7-10cm whenever the layer has broken down to less than 5cm.
FAQs
Can I mulch over weeds?
Pull or cut the worst before mulching. Persistent perennials need digging out, not covering.
Does mulch attract termites?
Termites don't eat woodchip mulch. Keep mulch clear of buildings as standard practice.
What's the best mulch for natives?
Coarse hardwood mulch or pine bark, depending on species pH preference.
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