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Mulching | The Secret to Healthy Trees

Updated: May 6, 2023

Improve the health of your trees by creating mulched garden beds to better the soil conditions.

 

Quercus suber with a mulched garden bed. Applied to assist with canopy decline.


Benefits of Mulching Trees with Whole-tree Mulch


Did you know that mulching your trees with whole-tree mulch can be a simple and affordable way to improve their health and growth? Whole-tree mulch is made up of leaves, twigs, bark, and wood, and acts like the natural debris found on the forest floor. This helps create a thriving environment for your trees and their surroundings, benefiting the soil and biota. Some of the benefits of mulching include enhanced plant growth, soil moisture retention, weed suppression, and even regulating soil temperature. It's an easy way to promote healthy trees and create a beautiful, sustainable environment.

Mulched garden bed under a corymbia ficifolia

Mulched garden bed under a Corymbia ficifolia


Mulch can also create areas of exclusion in public spaces, deterring people from gathering underneath high-risk trees.

 

Best Mulch to Use


The best mulch you can apply to your trees is organic whole tree mulch that contains all elements of a tree, leaves, bark, and wood, as it contains a good balance of carbon:nitrogen ratio that prevents nitrogen from being tied up in the mulch.

We recommend approaching your local tree company for large quantitates of mulch or enquiring with your local Council as they can occasionally have mulch that is freely available to the public. When acquiring mulch in this manner, it is best to be vigilant with the contents to avoid introducing any local weeds into your garden.

Other alternatives that are beneficial but less than ideal include euchi mulch, pine bark mulch, or hardwood mulch, these can often be found at your local landscaping store.





 

Types of Mulch to Avoid


Types of mulch that should be avoided are those that are typically brought for their appearance such red or black coloured mulch.

These are often made from recycled timber products such as pallets, that can contain chemicals and treatments like creosote or methyl bromide, these treatments prevent good soil biota and can create imbalances in the soil’s food web.

Playground mulch. Again, these are often made from recycled, treated timber products. Not good for trees or their soil.


Stone, plastic, grass clippings, and sawdust should be avoided.


Recycled Timber Mulch
Avoid mulches such as recycled timber

 


Applying Mulch


Undergrowth such as turf does not need to be killed prior to application. Do not apply weed matting as this will prevent the integration of mulch into the soil and negate most of the benefits that we are seeking.

When applying mulch, do not allow it to touch or build up around the trunk. As the mulch breaks down it can cause microbial decay that is detrimental to your tree.


Mulch should be applied in a consistent manner to a depth between 50-10 millimetres. Ideally, the width of the mulch should reach the dripline of the tree or further where possible. Do not apply mulch in a small radius around the tree as this has little to no benefit.


The application should be every one to two years, or as needed when the mulch breaks down into hummus—ideally maintaining the 50–100-millimetre depth.


Emerging weeds should be removed as they arise.


If the soil is dry prior to applying the mulch, it is best to give the newly laid mulch a good soaking as it can be resistant to water penetration but improves overall water retention once moist.


Magnolia grandiflora in a mulched garden bed




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