Tip over a good-size rock and what do you see? A patch of earth that is dark and humid, even on a hot, dry day. A throng of creatures — beetles, worms, ants — scurrying for cover, their busy underworld suddenly exposed to light.
Here’s how J.I. Rodale, one of the earliest proponents of organic gardening in this country, described that usually hidden landscape of soil protected by stones:
“A dampened darkness prevails that is wholesome for bacterial development, just as the gloom in luxuriously dense forests into which the sun rarely sifts generates an exuberant undergrowth of riotous plant-life.” He concluded that the surface placement of stones was one of the best things you could do for a garden.
As a beginning gardener, I considered stones a nuisance, pushed up from below as if by a demonic force. I hauled the largest ones out of my new garden with a winch puller known as a come-along, only to have new ones appear. I now know that earth does not produce stones, but stones produce earth — that is, the soil in which we grow our plants. Movement of glaciers, the pounding or seeping of rain, seasonal freezing and thawing, the action of dilute soil acids, the penetration of plant roots and the motions of soil-dwelling creatures all help break the stones down into mineral particles that our plants need to grow.
Stones in soil help it drain well. They protect it from erosion and evaporation of moisture. They cool the soil’s surface on a hot day, but upon absorbing some of the sun’s heat, help warm the soil at night — a fact especially important to a gardener wary of frost in spring or fall.
It was for all these gifts that Rodale wrote a little book in 1949 called “Stone Mulching in the Garden,” which included testaments of others who practiced that technique. Foremost among the benefits of stone-mulched soil, in Rodale’s view, were the management of soil moisture and the enhancement of underground soil life. In his own gardens, he revived an old custom of arranging stones around orchard trees, then went on to plant vegetables in rows, alternating with wider rows of stones.
Were you to mention stone mulching today, a very different picture would come to mind. It’s not uncommon for homeowners to have loads of crushed rock or “decorative stones” trucked in, then dumped and spread around wherever they don’t want grass or weeds to grow. The stones are too small, and weeds will grow in the stone mulch as leaves fall and decompose, thus providing a nursery where seeds can sprout. The more blended the stone mulch becomes with accumulating organic matter, the harder it is to remove when you realize your folly.
I can see trying an experiment in which I plant two similar young fruit trees and set large stones around one and not the other, to see which tree fares best. These would be big stones for efficiency, but not so large that I couldn’t move them around. I’ve often used giant granite cobblestones for garden paths in a vegetable plot. Maybe I’ll try Rodale’s trick of lifting them out now and then and putting compost or autumn leaves under them, to see how quickly earthworms turn the leaves into nutrient-rich castings. And maybe not. “Of course,” Rodale goes on to say, “if the compost is placed in the dirt-rows only, the earthworms will eventually distribute it throughout the ground.” With such generosity is a gardener’s labor repaid.
Damrosch is the author of “The Four Season Farm Gardener’s Cookbook”; her website is www.fourseasonfarm.com.