The Biscayne Times

Jul 18th
The Magic of Mulch PDF Print E-mail
Written by Jeff Shimonski, BT Contributor   
May 2017

Look around your yard for a great source of organic cover

GPix_YourGarden_5-17o to any neighborhood in Miami on any day of the week, and the most common sound by far will be that of a blower “cleaning” properties of leaves and other organic debris.

It’s nice to see clean neighborhoods, but why is all this organic material being blown into the street to go into the storm drains, or being sent directly to the dump?

The leaf litter and grass cuttings from your property constitute a great resource -- organic mulch -- that should remain on your property to break down and provide the roots of your trees and shrubs with nutrients and beneficial organisms.

I attended a lecture last year given by a horticulturist from the Singapore Botanic Gardens who extolled the great benefits of natural leaf litter. Horticulturists there had documented the benefits of leaving leaf litter underneath trees as mulch, as opposed to cleaning up fallen leaves so the gardens would seem “clean.”

The use of leaf litter as a natural mulch is nothing new. There’s quite a bit of science documenting the benefits to plants and trees by the organisms that decompose mulch. And the science of composting is itself quite sophisticated. The differences between the microorganisms that feed upon the green leafy stuff (nitrogen), as opposed to those that decompose the woody material (carbon) are well known, as are the resulting benefits to the roots systems of trees and other plants.

When you have all these organisms busy decomposing the leaf litter or mulch in and around the roots of your trees, you have what is known as a healthy rhizosphere, or root zone. These organisms help to exclude pathogens by taking up space or even preying upon those bad guys.

My goal in developing a truly sustainable landscape at Jungle Island, one that precluded the use of pesticides, fungicides, commercial soil amendments, or other such products, was predicated upon the use of compost and mulch to create healthy rhizospheres. This program actually succeeded, and we saved a tremendous amount of money by excluding horticultural chemicals.

My experience over decades of using mulch has taught me that all landscape programs for trees, palms, and shrubs should use this practice as a cornerstone of their horticultural maintenance.

What type of mulch do I recommend? I recommend the stuff that comes straight out of the back of the arborist’s truck.

Yep, not the stuff you can buy in the bags or by the pallet. Not the stuff that gets sprayed out of a hose and that can be dyed any color you want. Not the stuff that gets piled so thick or gets so stuck together that rain or irrigation water can’t get down to the roots of the trees.

Yes, everyone will know you spent a fortune on that kind of mulch, and you may get compliments on how neat it looks. But functionally, you’ll do better, in terms of plant health and landscape sustainability, with what you’ve got in your own yard.

You want a mix of material that is both green and leafy, and has a woody component as well. The organisms that decompose these different things will add diversity to your root zone. A rhizosphere that holds diverse organisms is a healthy one that can respond to most soil pathogens, either by eating or physically excluding them. That means fewer disease issues.

The organic material created as the mulch decomposes also adds a significant organic component to your soil. This organic stuff will also store more water for the plant roots. You won’t have to buy an artificial product to store moisture in the soil.

I once calculated that I applied over 100,000 cubic yards of tree-trimming mulch to the landscape at Jungle Island. This was over a period of about 15 years. We only irrigated once a week, never had to buy or apply fertilizer for the trees, and never had debilitating disease issues that necessitated spraying any trees.

Before you use this mulch, it’s very important that you let it sit for a month or so. In the early stages of decomposition, heat is produced and this can damage or kill plants and their roots. You don’t want to use mulch from a pile that emits steam when you pull the pile apart.

When you apply the mulch, only put down a few inches at a time. Don’t put mulch against the trunks of plants or trees, and do wet the mulch after you put it down. If you use fertilizer, pull the mulch back before applying the fertilizer; then wet the fertilizer and reapply the mulch. Don’t put the fertilizer on top of the mulch! So much fertilizer and money are wasted this way.


Jeff Shimonski is an ISA-certified arborist municipal specialist, retired director of horticulture at Parrot Jungle and Jungle Island, and principal of Tropical Designs of Florida. Contact him at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .


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