In the black mealy compost there was twenty worms in every shovelful, orange worms and purple worms threaded like screws. There were wigglers whipping in frenzy like raw nerves and long night crawlers that glistened like snakes, worms with swole bands and blister rings, worms that flattened at the edges.
—ROBERT MORGAN, This Rock, 2001
WHEN I GET HOME from a trip, the first thing I do is go outside and check on the worms. A pet-sitter takes care of our two cats, but I’m not even sure she knows about the existence of several thousand worms on the porch. They can easily be left alone for a week or two, as long as the temperatures are not expected to reach too far below freezing or too much above eighty degrees. The temperatures here hover in the fifties and sixties year-round. It’s the perfect climate for raising worms.
Before I leave for vacation, I add an especially thick layer of shredded newspaper to the bin, which keeps the bin from getting too wet, discourages fruit flies, and provides a little extra warmth if it does get cold. It’s not a good idea to add extra food since it might get moldy before the worms can get around to eating it. Besides, they can always eat the newspaper if they get hungry.
I came home from Ohio to find that the worms had nearly filled the top tray with castings. It was time to rotate the trays and spread the castings around the garden. I had Clive Edwards’s advice in mind; I planned to pile the castings up around the base of some old rosebushes that I’d inherited from the house’s former owner. I’m not much good with roses—I’d neglected them, and over the summer they’d become infested with whitefly.
I set the lid of the worm bin on the porch and pulled off the top tray. The second tray was filled with dark, spongy castings and lots of worms. A few melon seeds had sprouted and the young stems, blanched white for lack of sunlight, wove through the castings. I pulled those seedlings and tossed them onto my backyard compost pile with the rest of the garden waste, then lifted the middle tray off the bin and set it down as well, so that I could have access to the bottom tray. The worms had completely eaten through the food, but dozens of them still lived down there in their castings. I suspect that they prefer the bottom tray for laying eggs because it is so rarely disturbed; I can’t think of any other reason why they’d still be there. I lifted that tray off too. Below that was the bottom level, where water is supposed to collect until I drain it out by the spigot at the base. A few worms were slithering up the sides of the base, but I didn’t bother rescuing them. I figured that if they could climb down there, they could climb back up again. It was time to reassemble the bin.
The middle tray, where the food was nearly all consumed, went on the bottom. The top tray, where I’d been adding food most recently, became the new middle tray. And the bottom tray, with its payload of castings and a few dozen wayward worms, went temporarily on top. Before I could remove the castings, I’d have to get the worms out.
Usually I start by working through the castings with my spading fork to see how many worms I’m dealing with. There might be a dozen; there might be fifty or sixty. Often I turn up worm cocoons this way, too; I try to pick those out and drop them into the tray below, where I hope they’ll hatch safely. The worms themselves start moving into the middle tray as soon as I disturb their habitat. I leave the lid off the bin for a couple hours, which lets sunlight in, and I turn the castings occasionally to prod the worms into moving on. Within a few hours, most of the worms have left the tray and the castings are ready to use.
I used to let my castings dry out before I used them, but I found that they formed a hard crust when I did that and eventually turned into light, brittle chunks, like volcanic rock. I’ve discovered that it works best to use the castings right away, adding them to the soil while they’re damp. If I have anything to plant, I put castings in the bottom of the hole. Otherwise, I look around for plants in the garden that seem like they could use a boost and work the castings into the ground with a hand fork. This time I fed them to my roses in hopes that the whitefly problem would clear up. It’s never easy to dig anything into an established bed, but I did what I could, loosening the soil around the base of each rosebush and heaping worm castings around the roots.
Once I’d emptied the tray of castings, I quickly set it back on the bin and put the lid on top. I wanted to get back over to the roses. I had visions of whiteflies lifting off the bushes in one winged mass and vanishing from my garden forever. It didn’t happen that way, but believe it or not, after a few weeks, I couldn’t find a single whitefly in that rose bed. Now, as I write this, almost a year has passed, and there are still no whiteflies.
Next I’ll try the same thing with my broccoli and cabbage, which tend to get infested with greyish blue aphids once spring comes on. I can’t say for certain that worm castings will be the miracle cure, but I know one thing: I’ll keep experimenting until I find out. The worm population in my bin is now seven years along; many generations have lived there and reproduced. They are generating enough castings for all the experiments I’d like to conduct.
I’VE MADE A REAL effort to increase the earthworm population in my garden soil, too. I’ve brought in compost and mulch, I’ve planted cover crops and spread lime around to cut the acidity. After a while, I was ready to see if all my efforts to attract earthworms had amounted to anything. I waited for a damp, cloudy day when earthworms would be near the surface, and I went outside with a bucket and a shovel. I was going to take an earthworm census.
I picked a vegetable bed where I knew they would be plentiful and the ground would be loose and easy to dig. As soon as I turned over a clump of earth, I saw that my efforts with the soil had been rewarded: four or five huge nightcrawlers appeared on the end of my shovel, and several smaller worms—perhaps Aporrectodea caliginosa—ducked away from the light. The soil was perforated with holes about the diameter of a pencil—burrows. The worms, it seemed, had multiplied and occupied my garden soil in greater numbers than I could have imagined.
A ten-quart bucket sat next to me. I dug out enough dirt—and worms—to fill it. Once it was full, I sat down next to the bucket and started counting worms.
This hand-sorting technique can be time-consuming if it’s done on any large scale. There are other methods of sampling earthworm populations: a strong vibration will bring them to the surface, and some chemical extractors will also force them out of their burrows, although worms might not survive the exposure to chemicals. And as Sam James pointed out, wasabi and mustard will also force them to the surface. But I didn’t need any extraordinary measures to carry out this small earthworm count. Sorting them by hand would work just fine. In fact, it was a pleasant task, sifting through the bucket, examining the denizens of my garden soil up close. I was looking for worms, but I found quite an assortment of other creatures: ants, pill bugs, tiny spiders, and shiny dark beetles that scurried away before I could get a good look at them. There were cutworms and grubs and slugs, and tiny white specks I thought might be springtails. I held the larger insects in my hand and then set them aside, looking for worms. One thing was certain: it was crowded down there in the ground below my garden.
It took me about a half-hour to sort through the bucket and count the worms. I was careful to break up each clump of dirt to find the worms that might be burrowed inside. There were plenty of baby worms, along with about a half-dozen worm cocoons: sure signs that the worm population was healthy and ready to expand. I turned up close to a dozen six-inch-long nightcrawlers as well. In all, there were forty worms in my bucket.
If I wanted to do a truly scientific study, I would have chosen several different sites to sample: in addition to this fertile vegetable bed, I would have taken worms from the front yard, which is planted in perennials, and from the paths, where I have done little to increase the soil fertility. I might have even taken a sample from the alley behind my house, where the soil has probably not been disturbed for decades.
But I wasn’t interested in disrupting the earthworm community any more than I absolutely had to. Besides, I was mostly interested in knowing what kind of potential my soil had—what population size was possible if I brought in compost and manure, planted cover crops, and did everything right.
Most worm scientists describe worm populations in terms of worms per acre. Darwin estimated that there were fifty-three thousand worms per acre, and population studies performed in the twentieth century have shown that earthworm populations can range from as few as twenty thousand worms per acre in Rumania, to six hundred and seventy thousand in tropical rainforests in Malaysia, to an astonishing eight million worms per acre in a New Zealand pasture. And the experience of farmers and ranchers in New Zealand shows that where earthworms are abundant, crop yields increase.
It took a few minutes in front of the computer to convert my ten-quart bucket to cubic feet, and then (assuming that I was only really sampling the top twelve inches of soil in my garden), to calculate the square feet in an acre, and in the end, I calculated that if all the surrounding soil was as rich as the bed I dug, I’d have 5.2 million worms per acre. My house sits on a lot that measures about one-eighth of an acre. At that rate, there would be over six hundred and fifty thousand worms, almost a hundred times more worms than Darwin’s highest estimates.
What could this mean for the fertility of the soil in my garden? Estimates of the volume of earthworm castings deposited in the dirt each year vary widely and depend on the available food sources and the conditions—temperature and dampness—of the soil. One conservative estimate is that a single worm can eject a little over an ounce per year. That would work out to about 150 tons per year, per acre, which seemed like an extraordinary figure when I thought about Clive Edwards telling me that it would be too expensive for a farmer to import twenty tons of vermicompost per acre each year. (Of course, one critical difference between his studies and my estimates is that he was using a very high-quality vermicompost product made under controlled conditions, but the earthworm casts ejected by nightcrawlers in my own yard may be of a much different—perhaps lower—quality.) Also, I know that earthworms aren’t as abundant throughout my garden as they are in one enriched sixteen-square-foot vegetable bed. But even if I consider the fertility of that area alone, it is astonishing to think that the earthworm population of that bed—about two thousand—is capable of producing 125 pounds of castings for my vegetables every year.
Figures like these give scientists a good reason to see earthworms’ potential. They lend credence to some primitive notion, some early impulse, that tells us that worms must perform daily miracles underground. I have an old book called Humble Creatures that was written just after Darwin’s first paper for the Geological Society, but before the publication of The Formation of Vegetable Mould. The purpose of the book was to introduce readers to two humble creatures they might never have thought much about: the earthworm and the housefly. The author, James Samuelson, had a fervent admiration of the earthworm’s abilities, which was bolstered in part by Darwin’s own work. Samuelson quoted liberally from Darwin’s early paper on worms but concluded with his own graceful observation of the earthworm at work: “There it toils away, unconscious of its great mission, again and again penetrating the earth, and each time, when it returns to the surface, bringing up with it a small portion from below to aid in the restoration of the exhausted soil, and multiply the comforts of the human race.”
SURELY A CRATE of potatoes stored away for winter, a rich sweet orange, or an armload of deeply perfumed roses are among the great comforts of the human race. The earthworm plays some role in making all those comforts available to us. It is easy, I have found, to get a little sentimental when it comes to their contributions. Even a scientist can become consumed with a sense of wonder over the power of the lowly worm.
Since Darwin, one of the most ardent admirers of earthworms was a French scientist named Andre Voisin, who studied grassland ecology. He grew so enthusiastic about the achievements of earthworms that he published a paper in the early 1960s claiming that worms could be responsible for the development of the world’s great civilizations. Although his ideas probably seem a little crazy, I believe they might not be too far from the truth. Earthworms, he discovered, populated the Nile, the Indus, and Euphrates valleys in unusually high numbers. He concluded that great civilizations flourished in those areas in part because a healthy population of earthworms was present to work the soil.
“Civilisations could flourish,” he wrote, “in regions where the soil, to use Darwin’s words, had passed thousands of times through the intestines of active earthworms.” He went on to make what is perhaps the most surprising argument to date in favor of the accomplishments of earthworms: “Many members of the human community, instead of cultivating this land that had already been so well ploughed, were going to devote their time to the construction of buildings and to creating works of the mind.”
Voisin was not the first person to suggest that great civilizations spring up when the conditions are right, as if people are like gardens, blooming and expanding only when the soil is rich, the rain plentiful, and the climate temperate. He was influenced by Ellsworth Huntington, a Yale professor of geography, who wrote about the impact of climate and geography on the development of human civilization in his book, Mainsprings of Civilization, published in 1945. He drew maps of the planet on which zones of “human progress” were superimposed over zones of favorable climactic and geographic activity. The Nile, Indus, and Euphrates valleys ranked highest on his map of human progress. Fertile soil, he seemed to suggest, is a powerful agent for change. It feeds people, and once they’re fed, they can go about building a new society for themselves. People can live closer together and share the labor of farming, even creating specialized jobs (blacksmith, baker, carpenter) and, eventually, developing tools and technology to make those jobs more efficient.
If all of human progress springs from good soil and warm summers, shouldn’t earthworms get some of the credit? Voisin thought so. Thanks to them and their ability to plough the soil, he reasoned, people were, for the first time, free to devote their spare hours to the development of math, science, a written language, and even the construction of the pyramids in Egypt.
Voisin was a first-rate earthworm romanticist, lavishing praise and poetry upon them. I can’t help but admire his vision, his faith in what an earthworm could do. One of the great snippets of earthworm poetry comes from Voisin, when, in the middle of an otherwise ordinary chapter on earthworms and agriculture, he conjured up an image of Hamlet and Horatio standing on the terrace at Elsinore and discussing the lowly earthworm’s achievements:
[T]his evening there is no mention of the ghost that walks the terrace by night. The light of the moon suddenly falls upon an earthworm sliding under a stone, and Hamlet asks his friend:
“Did you know, Horatio, that without earthworms men could not create civilisations?”
With characteristic scorn Horatio answers sarcastically:
“Until now I thought that earthworms were destined to destroy the last traces of human civilisation, devouring men’s corpses and swallowing up their buildings.”
To which Hamlet replies once more:
There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy.