Gardening in Rock and Clay


This is the mix of rocks and sand that central Wisconsin gardeners deal with. Good drainage to beat the band, but not much else! For those who garden in a sandbox, organic amendments such as compost and manure are essential

When my husband and I first moved to Columbia County, New York, we knew that we wanted a large vegetable garden. We asked Albert, a neighbor who was a farmer, to help us prepare a patch of our land. In the spring he brought his equipment in to grade our future garden. As the work proceeded, cars and pickup trucks that were driving down our road began to stop; people had recognized Albert’s truck and backhoe, and pulled in to see what was going on.

Soon my husband and I were standing with four or five men we didn’t know, watching Albert work. After awhile, one of the men turned to us and shook his head. “Some people got the rock,” he said solemnly, “and some people got the clay. You got the rock and the clay.”

We did indeed. In the eleven years that we lived and gardened on Pratt Hill Road we coped with both. When we wanted to plant a shrub, it took a pickaxe and a strong back to dig the most minimal hole. Whenever I purchased a perennial and saw that the tag said, “Needs good drainage,” I’d roll my eyes. Good drainage? What’s that?

In the years that I gardened there, I learned how to deal with, and yes, appreciate, the clay and rock that is common in many parts of the country. For those of you who are gardening in similar soils/rocks, I offer you the following suggestions:

  1. When creating new beds, amend the entire bed with compost or composted manure before planting. If there are rocks that cannot be moved, dig around them as best you can. Dig the amendments down as deeply as you can, knowing that sometimes you’ll dig the compost in to five inches and other times twelve inches under. Do the best you can.
  2. Apply an inch of compost over the surface of established gardens every year. This will amend the soil from the top down. Mulch can be applied over the top of this compost or composted manure if desired. The mulch will also amend the soil as well as preventing weeds and conserving water.
  3. Chopped leaves make excellent soil amendments and mulch. They do not make soil more acidic.
  4. Take advantage of slopes: place those plants that prefer good drainage on a slope so that the water does not stand around roots. Many plants that require good drainage will survive in clay if they are on an incline.
  5. Grow marigolds in clay that isn’t easily turned over – the marigold roots penetrate heavy clays, loosening the ground for future gardens.
  6. These are a few of the plants that thrive in clay soils: Lilacs, ninebark, elderberry, forsythia, dogwoods, spruce, white pine, willows, arborvitae, bee balm, black-eyed Susans, daylilies, hosta and perennial asters.
  7. Do not automatically add gypsum to your soil because someone tells you it will “lighten clay.” Gypsum can lead to deficiencies of other elements such as iron and manganese, and have negative effects on mycorrhizal fungi. See this website for more information:
  8. If there is so much rock that you can’t plant around it, or if the clay is so dense that there is standing water in most of the year, consider building raised beds, especially for vegetables and cut flowers.
  9. Start with small plants. If a plant has to get established in less-than-ideal soil, it’s often easier for it to do so if it’s raised in that location. We’ve all seen plants that are growing in the crack of a rock, or the tiny space between an asphalt driveway and a cement foundation. Sometimes plants succeed in the most unlikely situations, but if they’ve been there since infancy they often adapt more easily.
  10. When I gardened in “the rock and the clay” I found that with the regular addition of organic matter (compost and mulch) I did not have to fertilize my gardens. Clay soils hold onto nutrients more than porous, sandy soils do, so if you garden in clay you may be able to use less fertilizer on perennials, shrubs and trees. Having a complete soil test done so that you know what you’re starting with is always a good idea.
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