What Is an Adequate Mulch?

Nature will always be the best school for understanding plant needs. It functions autonomously, following ubiquitous and interrelated environmental rules that enable the entire ecosystem of a given environment to be in perpetual equilibrium.

Most of the problems we encounter in our crops are caused by the disruption of this balance. I’ve noticed that all the planet’s ecosystems, where the five vital plant parameters are present, are occupied by plants. Soils are never bare. The vital parameters are: water, air, soil nutrients, heat and light. With these elements, plants build their habitat, creating what I call: Nature’s Shepherd’s Pie. If you’re unfamiliar with this dish, it’s a layering of three main ingredients: ground meat, creamed corn (or corn kernels) and mashed potatoes on top. Whatever the recipe, this comparison is to make the point that wherever there are plants on the planet, you’ll always find three distinct layers of ingredients. It’s like that everywhere, except too often in our own cultures.

Nature’s Shepherd’s Pie

Wherever there is a natural vegetation cover on the planet, there are three distinct layers of matter, each playing an essential and complementary role. If one of them were absent, we’d have to forget plant life and, consequently, animal life as well as our own, that of humankind.

1. The Support Layer for Plants: Mineral

Sand, clay, silt, black earth and even rock… plant life settles on all these minerals. This layer serves as a support in which (or on which, in the case of rock) plants attach themselves and extend their roots to draw water and minerals up from the soil, or circulate on and in the interstices of the rock, thanks to the phenomenon of capilarity.

2. The Living Nutrient Layer: Humus

Made up of decomposed and decaying organic matter, this layer contains what we call compost, but much more than that. This layer is inhabited by a living ecosystem that is busy transforming dead plant tissue into compost and mixing it with the top few centimetres of soil, creating rich soil on top of poor subsoil.

3. the Protective Layer: A Mulch of Dead Plants or Ground Cover

It’s both the layer that protects the nutrient layer and contributes to the forming of humus. It’s this protective layer that nourishes life in the soil and contributes to its fertility. This is the layer we’re talking about in this article.

The layer most often neglected is the top layer. This layer is made up of living and dead plants. In natural ecosystems, there is always both. In our cultivation practices, there is often only the living form of plants, the ones we grow, and we attach little or no importance to the layer of dead plants we call “mulch”.

Six Advantageous Characteristics

There are several categories of mulch on the market.

From an environmental standpoint, a suitable mulch should have these six advantageous characteristics:

1. It must come from plants

In nature, all mulch comes from plants. It’s always dead plant tissue that forms mulch. Look at the leaves on trees in the woods, or the dead grasses in wild meadows. The use of plastic, geotextile, crushed stone or rubber shavings doesn’t automatically lighten the load, and doesn’t provide all the benefits of a natural mulch.

2. It should resemble as closely as possible the plants to which it is applied.

What kind of mulch do you find in a maple forest? In a coniferous forest? In a wild meadow? If we follow environmental logic, does it make sense to apply conifer mulch to herbaceous plants?

3. It must decompose quickly

In the natural world, what goes to make up mulch eventually becomes plant food. The mulches used must therefore decompose quickly enough to allow the plants to self-fertilize, unless you insist on buying concentrated fertilizers and compost, which are costly both in terms of money and the environment.

4. It must be available

Once again, for environmental and economic reasons, it would be preferable for the mulch used to be readily available in sufficient quantities, without the need for long-distance transport. It must be available in sufficient quantities to supply all those who need it.

5. It must be inexpensive

Who wants to invest a fortune in their flower beds and garden, when there’s another way? Since the mulch used has to decompose quickly to ensure self-fertilization, if it has to be expensive, not everyone will be able to afford it, especially since expensive mulches are precisely those that are least available.

6. It should be made of materials that are not or only slightly decomposed, not too coarse and remain aerated.

To prevent the seeds of undesirable plants trapped in the mulch from germinating, the materials making up the mulch must be able to dry out between rains. That’s why it’s essential to keep the mulch aerated.

On the other hand, if the mulch materials are too coarse, aeration will be too great and the soil will dry out. What’s more, this type of coarse mulch will be less stable in the wind. This means you’ll have to apply a layer of mulch that’s too thick, which will lead to other problems.

Finally, if the materials used are at too advanced a stage of decomposition, the mulch will no longer play a protective role, but will become, as happens in nature, a nutrient layer and, consequently, an excellent germination medium. Moreover, organic matter is likely to be wasted, as it will become humus on the surface and blow away with the slightest gust of wind or a good rain, contaminating run-off water rather than serving as food for your plants.

Analysis of mulch types according to environmental characteristics

Mulch type	Organic origin	Similar*	Rapid decomposition	Availability	Low cost	Aerated materials
Cocoa husks	Yes	No	Yes	No	No	No
Buckwheat hulls	Yes	Yes	Yes	No	No	No
Pine bark	Yes	No	No	No	No	No
Cedar, hemlock, pine mulch	Yes	No	No	No	No	No
RCW (ramial wood chips)	Yes	No	Yes	No	No	No
Decorative or volcanic stone	No	No	No	No	No	No
Cereal straw	Yes	Yes	Yes	No	No	No
Shredded tree leaves	Yes	Yes	Yes	Yes	Yes	Yes
Freshly chopped herbaceous plants	Yes	Yes	Yes	Yes	Yes	Yes

Returning Dead Plant Matter to the Soil

The return of dead plant matter to the soil is the hallmark of everything in nature. Without this return of dead tissue, plant life could not exist. This is part of the great circular consumption process, where nothing is lost and nothing is created in nature. Ignoring this obvious environmental fact exposes us to increased maintenance and endless expenditure on products that have a negative impact on the environment, whatever they may be.

Personally, the only materials that enter my gardens are the leaves from the trees and herbaceous plants in my immediate environment. I manage them as resources, not as waste. I do this not out of laziness, but out of common sense!

I hope you enjoy your environmental gardening!