The Concept of Mulch

 Early landscape at my former Seminole home. Not everything has to be mulched

My former backyard in Seminole. Using leafy mulches quickly changed the nature of this once-poor soil.

Across this nation (and I suspect a great many others) there is an almost-religious obsession with using mulch throughout our garden plots. It is one that I've always had a difficult time understanding. In my opinion, mulch is too frequently used for the wrong reasons.
It is true that there are real purposes to the use of commercial mulches. In a very formal setting, it has aesthetic value. It helps to define the planting bed - separating the "real" plants from the empty space between them. It also can help in weed control if applied deep enough and if kept up as the mulch layer decays. For gardeners that desire this "lack-of-plant" bare space between their plantings, it can save weeding time. That's just not my type of gardening. In a living landscape, the open space between your plants should provide value to the natural world in the same way that your plants do, and commercial mulches defeat this purpose.
In the natural world, mulches form from leaf drop. Here in central Florida where I now live, that often means oak leaves or pine needles. Commercial mulches are generally wood chips of one kind or another - pine bark, chipped (and sometimes dyed) pine wood, chipped Melaleuca, or (heaven forbid) chipped cypress. These woody mulches are designed to form an aesthetic covering that lasts; defined as "does not decay quickly", but it is that exact reason why they have no purpose in a living landscape unless used strictly in walkways or other high-traffic areas. In a living landscape, mulches are supposed to decay easily. By doing so, they enrich the soil and feed the myriad organisms within the soil that plants depend on.  Wood has very few nutrients in comparison to leaves and it takes a lot of energy to decay it. The lost energy from the "system" and the very poor return on its investment are hindrances that every gardener should avoid. There simply is no logical reason to use mulches that don't quickly decay.
Soil is far more than the mineral grains that compose it. Though most soil is a combination of sand, silt and clay with spaces for air and water, it also contains organics derived from the decay of leaves, needles, twigs, and the like. Organic particles are not necessarily rich in nutrients as some might assume. Most plants pull most of the important nutrients out of their leaves before discarding them. That only makes sense as this is a planned activity by the plant and these nutrients are important to its survival. What is left gets released back into the soil once decomposition is complete. Feeding this decomposition process is the real value of mulches that decay.
Healthy soil has a phenomenal number of different organisms that decompose organic matter. Various soil bacteria, fungi, nematodes and earthworms are absolutely necessary for plant roots to function effectively. Though we are often led to believe that many of these are plant killers, the truth is that very very few are. Most are absolutely necessary.  I've written about them extensively in my new book, The Nature of Plants: An Introduction to How Plants Work, and I won't repeat it here.  Suffice to say, we strengthen the health of our plants when we grow them in healthy soil. Healthy soil, by definition, has to have a diversity of microfauna and we create and feed that microfauna by giving it organic material to feed on. The broad use of soil insecticides and fungicides is one of the worst practices we can incorporate if our intent is to have healthy plants and a living landscape.
The soil at my former Seminole home was extremely unhealthy when I first moved there. Some of it was the original soil pre-development, but much of the rest had been altered by the addition of "fill."  To save money, the original owners had obtained this fill from pretty sketchy origins. Plants that I first installed failed to thrive; many simply died. Parts of the landscape took me several years to find a plant species rugged enough to survive over time. During these years, we collected the leaves and pine needles raked off the yards of our neighbors and set along the curb in plastic bags for disposal. This is a common practice that I've witnessed everywhere I've lived; raking the downed leaves and needles off your landscape and sending them to a landfill.  It is one of the most nonsensical landscape practices that I can think of. For the first few years, our trees and shrubs did not produce enough of this natural mulch so we took the labors of our neighbors and spread it across the relatively bare areas of our developing landscape - spreading it just deep enough so that it would completely decay in the year ahead. The difference in our soil and its affect on our plants was quickly noticeable. Each year, I suspect we discard thousands of tons of valuable organic matter to landfills instead of collecting it for use in our landscapes. We are "penny wise and pound foolish" when it comes to how we view our organic "waste." If we are to rake our leaves and needles, we should be stockpiling it somewhere in our landscape for future use or composting it directly to be spread out over our soil.
Last (for this entry anyway), we should not think of mulches as something that needs to cover up all the bare spots in our yards or to be put down so thickly as to prevent the germination of weeds. As I've written previously, bare ground is absolutely essential for most of our native bees. While some of the more "glamorous" species, like honeybees and bumblebees are colonial, the vast majority of our native bees species are solitary and nest in the ground. These need bare ground to excavate their brood burrows and lay their eggs. Birds need bare ground to dust in. Thick layers of mulch, even the "good kinds", prevent these important elements of a living landscape. It also prevents the reseeding of wildflowers in a wildflower meadow.
Use mulches thoughtfully. Understand the role they play and respect that. By doing so, you will see an astounding difference in the health of your landscape.

Leafy mulch in the wooded part of my former landscape in Seminole

This all-too-often site needs to end.