I am sure there’s a systematic way to add to, aerate, and otherwise mix my backyard compost heap in the most efficient and productive way possible, a process with inputs and variables that could be modeled by an AI computer program, spit out, and followed—commercial composters take just such a scientific and mechanized approach to their operations. But my pile is artisanal. It’s handmade in small batches and sampled throughout the year but mostly harvested in one fell swoop by late summer.

The recipe varies from year to year, as does its specific cooking time. Some parts mature early, and most springs I can harvest a wheelbarrow or two of fresh, ripe compost for the first sprouts in the vegetable garden or new transplants in the perennial beds or to fill the holes left by rocks I pluck from the lawn through mud season. Creating each new vintage is part art, part science. Mostly it’s about mixing air, water, and sundry organic ingredients by turning the heap inside out, in place, with a minimum of fuss and to maximum effect. It’s a sport-like hobby, a pastime that engages me both spiritually and physically.

However much I labor, my puny efforts pale in comparison to the true workhorses of my pile: earthworms. They are peerless in chewing their way through rotted organic matter and turning it into humus. Truth be told, new soil is mostly worm poop. The worm castings that dot my still-dormant lawn in early spring are ample evidence of this handiwork. Gutwork might be a better term to describe the inexorably dogged pursuits of the class act that is Oligochaeta.

“A worm is an animated intestine,” Steve Jones writes in The Darwin Archipelago. “The body is hollow and filled with fluid, with a long digestive tube down the center. Aristotle described worms as the ‘Earth’s entrails.’ Cleopatra decreed them to be sacred animals and established a cadre of priests devoted to their well-being. [As Darwin’s book put it], ‘All the vegetable mould over the whole country has passed many times through, and will again pass many times through, the intestinal canal of worms.’”

Worms are the invertebrate backbone of my pile, and I strive to make the heap hospitable to the herd that resides within it. Lowly as they are, worms are near the top of the compost bio pyramid, and they lead the way in deconstruction, perforating the layers with their burrowing and churning out countless castings along the way.

In form, my open-faced pile may look like a heap of brown leaves mixed with green trimmings, but it functions more like a coral reef, with worms standing (or squirming) in for the multitude of polyps that crank out limestone deposits that, in turn, become the base of an entire ecosystem. Worms do the same on dry land, and what they leave behind is soil.

Charles Darwin may be legend for loftier theories now, but during his life, he had a lot to say about earthworms. His book The Formation of Vegetable Mould Through the Action of Worms, With Observations on Their Habits, published in 1881, sold even better than On the Origin of Species during Darwin’s lifetime. His thesis? “It may be doubted whether there are any other animals which have played so important a part in the history of the world as have these lowly, organized creatures.”

Darwin biographer Jones explains the math. “An acre of rich and cultivated ground is riddled by five million burrows. Half the air beneath the surface enters through burrows, and water flows through disturbed soil ten times faster than in unperforated. In an English apple orchard they eat almost every leaf that falls—two tons in every hectare each year. In the same area of pasture, they can munch through an annual thirty tons of cow dung.”

The earthworm is an eating machine that is a marvel of simplicity. It uses sand in its gizzard to grind up tiny bits of organic matter and the bacteria, fungi, and nematodes that live on it. Moistened with a spit of liquid calcium carbonate, this microscopic gruel travels to the worm’s intestine, where bacteria digest it, sending nutrients into the bloodstream and everything else out the back end.

Vermicastings are 50 percent higher in organic matter than soil that has not traveled through an earthworm. “This is an astonishing increase and radically changes the composition of the soil,” write soil experts Jeff Lowenfels and Wayne Lewis in Teaming with Microbes: The Organic Gardener’s Guide to the Soil Food Web. A worm’s ability to increase the availability of nutrients “is about as close to alchemy as it gets.”

“The worm’s digestive enzymes unlock many of the chemical bonds that otherwise tie up nutrients and prevent their being available,” the authors continue. “Thus, vermicastings are as much as seven times richer in phosphate than soil that has not had been through an earthworm. They have ten times the available potash; five times the nitrogen; three times the useable magnesium and they are one and a half times higher in calcium. They shred debris so other organisms can more readily digest them. They increase the porosity, water-holding capacity, fertility, and organic matter of soils. They break up hard soils, create root paths and help bind soil particles together. They cycle nutrients and microbes to new locations as they work their way through soil in search of food. A noticeable worm population is a clear sign of a healthy food web community.”

Even so, it boggles my mind to know that earthworms are accidental tourists in my pile, having landed on these shores from the baggage of European settlers and the ballast of the ships that brought them here. The glaciers of the last ice age, a mile thick above my home in southern Connecticut 10,000 years ago, scrubbed virtually every soil-dwelling worm from much of North America.

To the Old World earthworms, this truly was the promised land, and in they rushed, colonizing new ground at 30 feet a year. Some soil scientists lament how dramatically they’ve displaced native creepy crawlers, both above and below ground, as they munch through the forest floor. (As it happens, gardeners and even earthworms are now facing a fight from a voracious new colonist, a worm from Asia that grows to six inches and is so hyper in its movements that it’s known as the jumping worm. It was imported in the 1940s from Japan to the U.S. by the Bronx Zoo to feed duck-billed platypuses.)

Arriviste jumping worms aside, all those trusty old red wrigglers and nightcrawlers will always have a home in my backyard compost heap. As E. O. Smith said of earthworms, ants, and their ilk, “Each species is a masterpiece, a creation assembled with extreme care and genius. They are the little things that run the world.”

After starting his epic study of worms at his estate in the English countryside, Darwin went off on the Beagle and came back with the theory of evolution. I will stick closer to home and tend to my pile and the worms within it, as they do the real heavy lifting in turning a heap of dead leaves and recycled greens into rich new earth.

Scott Russell Smith is the author of “On Compost: A Year in the Life of a Suburban Garden” (Christmas Lake Press, 2024), from which this excerpt was adapted.

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