Mulch Ado About Nothing
Updated: Jul 17, 2022
Aristotle coined the idiom ‘Nature abhors a vacuum’, to illustrate his belief that empty and unfilled spaces are unnatural — that where there is nothing, nature wants there to be something.
Smart man, Aristotle. Indeed nature is self-regulating. Ask anyone who ever tried to maintain the unnatural perfection of a weed-free expanse of lawn or freshly tilled vegetable bed, or dared to imagine that the neat and tidy seams between newly laid patio pavers would not eventually host all manner of growing things.
From what I have observed over five+ decades walking about in nature, old growth forests, urban parks, and in our home gardens is that, nature feeds, heals, nurtures and perpetuates life by continuously chopping and dropping into every nook and cranny — cycling nutrients and biomass in layers upon layers, season upon season, year upon year, so that the web of life remains uninterrupted both above and below ground.
This natural process is, as I see it is ‘mulching en-masse’, in all forms and in all places, utilizing every biotic (living) and abiotic (non-living) thing on the planet — on land and at sea.
As a rule, where there is no mulching or layering of organic matter, there is little life to speak of, or no life at all.
On land, natural mulching and layering creates deep and complex strata of nutrition for the basement level of feeders — known officially as the first ‘trophic’ level. Rather like a double-decker buffet for the minerals, microbiology, fungi, insects, bacteria, worms, etc that comprise the soil, as well as the plants that live in and on it.
Second trophic level herbivores and plant eaters such as birds, rodents, large insects etc, dine on level one plants and life forms. Third trophic level carnivores and meat eaters like reptiles and small raptors dine on level two life forms. Fourth trophic level carnivores like coyotes dine on level three life forms, and then ultimately, Apex level predators like lions, wolves, etc, dine on level four and below.
There are exceptions of course — large ruminant herbivores such as cattle and sheep that dine on plant biomass exclusively, and omnivores that gain food energy by consuming plants and animals from all levels. In general however, the food energy pyramid (and the trophic feeding levels within it) is built on a broad foundation of numerous small creatures, and ascends ultimately to an attic apex containing fewer and much larger creatures.
At every level, life forms eat other life forms, and then get eaten themselves by larger life forms or die and get eaten by basement level feeders who get eaten by next level consumers. It is a big, beautiful, complex, cyclical system of life and death, and regeneration.
Critically, the entire energy food pyramid and web of life rely on trillions and trillions of beautiful and largely invisible workhorses known as decomposers. Decomposers (fungi, bacteria, invertebrates, worms, insects) break down and reduce all things that fall to the ground lifeless — animal waste, carcasses, leaves, fallen trees, rotting fruit, rocks, etc — into nutrient food energy, using the sun and the rain in the doing. Decomposers live in the soil, protected and fed by mulch.
Pull back the top layer of forest floor ‘mulch’ anywhere in the world to see the miraculous world of decomposers at work. Decomposers also live in and on things that live in and on soil — dead and dying trees and animals, ancient civilizations, rocks, etc, turning everything ‘eventually’ into or back into living soil.
Crazy amazing, right? Nature is insanely intelligent.
The best part is that, versions and variations of mulch can help us solve both big picture problems related to climate change, and little picture problems like how to hold water in our food and flower gardens while at the same time fertilizing them organically.
When it comes to regenerative gardening in urban environments, the subject of mulch figures prominently as it relates directly to the conservation of water and the improvement of soil biology and native habitat.
I have learned, through an ongoing process of trial and error, which mulches works best in particular spots in our home gardens, which mulches deter pests, which mulches capture and/or retain moisture, which mulches best regulate soil temperature during extreme heat and cold events, which mulches best provide and contribute to native habitat, and which mulches contribute to micro and macro ecosystem health.
Understanding and incorporating mulch goes hand in hand with understanding soil as a living, breathing, dynamic entity that requires shelter from the elements in the form of a roof-like mulch layer.
Weeds are so-called living mulches, sent by nature to fill a void and kick-start a nitrogen-boosting cover crop cycle in areas of disturbed soil. No-dig and no-till gardens (in which the soil is mulched but not dug up or turned over), are for the most part weed-free zones because buried weed seeds remain dormant, hidden from the germinating influence of sunlight.
Leaf litter, forest duff, pine needles, seed pods and cones, and moss are beautiful examples of mulches made by nature.
Here in the temperate rainforest, we grow a lot of moss. Ironically, we also experience drought for two months or so most summers, during which the moss forms a sort of biological soil crust, integral to moisture retention and soil fertility.
I first noticed this phenomenon along the margins of the forests surrounding our neighborhood. On very hot days, we would take the children into the forest and walk the trails along the river. The temperature would drop immediately upon entering, and the hot, dry and naked ground on the outside edge of the woods would become cool, moist and spongy underfoot, more-or-less right on the line of transition.
'Observe and interact' — the first of 12 principles of permaculture.
Today in our gardens, we utilize and encourage native mosses and naturalized native ground covers, pretty much anywhere they wish to grow, except for the raised food beds. They are lush and beautiful, and provide valuable native habitat for billions of microorganisms, insects, small animals and birds. They thermoregulate the soil, and retain moisture.
We use chopped, clean straw mulch in our vegetable beds, pots and containers. The cleaning and machining of the straw breaks down the lignin, softening it and helping it stay put and absorb (then release) moisture. On average, we can reduce watering by up to 75% in straw-mulched areas.
In our front garden, there is a bird bath in the centre of a path intersecting six raised beds. I often see birds nestled in the soft straw mulch in the beds, basking and drying their feathers in the sun. Admittedly, the birds discovered and then nibbled my first two sowings of peas, but I remedied that by wrapping bits of recycled foil around the twigs I was using as trellises.
Contrary to conventional wisdom about straw mulch attracting slugs, we find that it repels them as they get rather stuck up in the short pieces. The air trapped inside the straw tubes acts as insulation, cooling and regulating soil temperature during summer. During winter, the straw breaks down easily (four times faster than wood chips) into soil nutrition when covered with a thin layer of vermicompost and/or cover crops like broad beans, mustards and winter greens and lettuces.
We use native alpine, woodland and coastal strawberries as living mulches in areas were soil is at risk of erosion or is heat-stressed butting up against paving. The plants naturalize quickly, provide food for birds and our little veggie dog Dave, and look lovely as they wander across paths and paved areas.
Annual sweet alyssum planted under berry bushes and dwarf fruit trees, spreads quickly to form a living mulch carpet of natural biological defense, attracting pollinators and beneficial predator insects.
In our new rain garden, we used pea gravel as an interim mulch and to keep weeds at bay while the native bog plants get established. Because the area floods during rain events and is underwater for much of the winter, my thinking was that gravel would mimic the rocky riparian edge of stream beds and help prevent the soil from washing away. The beautiful nodding onions are naturalizing like wildfire, grabbing onto and knitting the tiny pieces of gravel into the soil as it goes, building structure and increasing porosity. Crazy amazing, right?
Recently, after visiting Terra Flora Soil Works in Chilliwack, where Andrew the soil farmer grows all manner of living soil, inoculants and mulches, I was inspired to use some hazelnut shells that he had sourced from a local farmer, as a top dress of decorative mulch in our terracotta potted dwarf fruit trees. The nutty topdress looks quite elegant and further insulates a three-inch layer of native woody mulch. It is particularly important to mulch soil in unglazed clay pots, as the soil dries out very quickly.
Annually, in all of our gardens not covered by moss and groundcovers, we add a one-inch mulch layer of organic composted soil enriched with worm castings and fungi. Additional mulches like straw are added on top of this primary mulch.
In the new boulevard ecosystems — one Garry oak, and one pine woodland — that we created this year in place of two separate areas of lawn that were removed, we (I) nerded out a bit with mulch.
We created a custom ‘native mulch’ to cover and protect a six-inch deep layer of organic composted soil that we applied where just four months ago there was lawn. Using a three-inch mulcher/shredder, we ground site-sourced pine cones and needles, fern trimmings, dried broadleaf evergreen leaves, and oak tree trimmings, and then combined that dry mulch one wheelbarrow at a time 1:1 with two-year old fungi-inoculated composting mulch from Terra Flora Soil Works.
We produced and applied about six cubic yards overall of the blended mulch mix and then wetted it through with a compost tea made from the vermicompost, a local sustainably harvested kelp (Macrocystis integrifolia) concentrate, and a soluble blend of eighteen different species of Glomus, Gigaspora, Rhizopogon, Pisolithus, Laccaria, and Suillus fungi from Organic Gardener’s Pantry on Vancouver Island.
Finally, because Garry oak trees are tap rooted and notoriously difficult to transplant, we incorporated soil taken from beneath our neighbour Robert’s towering Garry oak, into the soil beneath our three newly transplanted Garry Oaks, and then boosted it with a watered-in sprinkling of insect frass (black soldier fly poop) that Andrew gave us. The practice of transplanting species specific soil microbes and fungi from an established ecosystem to a new one is not uncommon in professional organic landcare circles, but is new to me.
Making native mulch at home was a biomimicry experiment inspired by permaculture and its observation of and deference to nature’s logic. Our hope was to accelerate the decades long process forests undertake in creating nutrient-dense humus, and assist the three Garry oaks in particular, in establishing healthy root systems and mycorrhizal networks between themselves and other newly planted native shrubs, perennials and ground covers.
It is early days yet, but the experiment seems to be working. Hundreds of thousands of tiny mushrooms, plus algae, moss, and accelerated plant growth indicate ecosystem happiness, and we are seeing greater numbers and species of insects and birds than we have ever seen on our property.
Two of the Garry oaks have leafed out, and the third is still slumbering but otherwise healthy. Research indicates that transplanted oaks can remain dormant for several years, spending all of their energy below ground, establishing robust root systems.
The pine woodland ecosystem is coming into its own, receiving daily doses of nature's own pine duff mulch from above, incorporating it into the custom blend that we planted it in. Eventually, it should look as though it grew up out of the landscape, unaided.
Hopefully, the successes, failures and learnings from our native mulch creation experiment will assist gardeners in the future as they attempt to reforest and rewild, creating much-needed native habitat and mitigating the impacts of climate change.
Until next time, happy mulching. Start small and grow big.