Sara Pitzer - Gardening in Clay Soil

Never Work It Wet!

To understand why not, watch a potter at the wheel. Shell take a lump of wet clay, throw it onto the wheel, wet it some more, then wet her hands before she starts turning. As the pot takes shape, she repeatedly spreads water on it. The water helps firm the clay tighter and tighter, alters its density so that, when heated, it will become solid as a rock. I came to this understanding late because the clay in the garden seemed so easy to handle when it was wet.

My first clay garden baked into a brick in the Carolina sun. Even the rudbeckias looked spindly. It has taken me several years to undo the initial damage and loosen up the clay so that it is fertile. Now Ive got good soil, earthworms, and healthy plants, but even that doesnt mean I can just plant a few seeds, sit back, and enjoy the benefits of my earlier labor. Keeping clay friable is an ongoing process.

Although gardening in clay presents serious challenges, clay has its advantages, too. First, clay tends to be fertile. Amish farmers looking for new areas in which to settle favor clay fields because they so often yield productive crops. Also, clay, unlike sandy soil, holds moisture, retains nutrients, and anchors plant roots securely.

Both the benefits and the problems are the result of clays basic character: it is composed of extra fine particles which stick together tightly. The gardeners challenge is to loosen the mass. The worst thing to do is to till it and douse it with chemical fertilizer. Even if you get a crop the first year, youll find diminishing results and deteriorating soil in subsequent seasons. I learned this when my family lived in a house surrounded by cannery farms.

These farms grew large quantities of peas and beans. Every year the farm managers used heavy equipment to work the clay loam fine enough to get seeds in. Then they followed with a heavy program of liquid fertilizers, weed killers, and powerful insecticides from before planting time until harvest, when they returned with more heavy equipment.

The workers were nice people. Every year they brought us bushels of peas, beans, shoepeg corn, and tomatoes. Without exception the vegetables were tasteless and had a texture like Styrofoam. In ten years I watched those fields become hard and cracked, streaked with gullies and bristling with thistles as everything washed away except the clay. The day after a rain the surface of the fields felt as hard as cement. The last I heard, the fields were no longer used at all.

This was made all the more dramatic because right next door an Amish family had a cornfield and a truck garden. The Amish, too, used commercial fertilizers, but they also spread a lot of manure. And, of course, the Amish worked the soil with mule-drawn plows. Their gardens were breathtakingly beautiful. Their produce attracted buyers from all over the county. Watching what happened under these two different treatments was an eye-opener.

You can have a good garden in clay if you use elbow grease rather than heavy equipment to loosen the clay; if you enrich it and improve its tilth; and if you use long-term strategies to maintain the health of the soil. Use a tiller or turn the earth in beds with a spade and improve the soil with both commercial products and natural materials from your own locale. But number one, you should never work it wet.

Once you have stopped working clay soil wet, the next step is to improve the composition and structure of the soil by adding inorganic and organic materials to make it less dense.

The following inorganic additives act as barriers to keep clay loose by getting between the clumps so they cant stick together. My reading and experience suggest that you need to replenish such materials every few years because they gradually disappear from the soil. Ive never quite figured out where everything goes. At least not things like sand and ashes.

Dont ignore the standard advice to take soil tests before beginning your garden to check the pH and to spot mineral or chemical imbalances. Clay tends to be slightly acid and applying a light dusting of lime, in the form of ground limestone or dolomite, is standard practice for many gardeners, except those who plant lime-hating plants such as blueberries. In addition to raising the pH of clay to make it less acid, lime makes the clay particles come together in larger clumps, creating looser, less dense soil.

Also, lime releases phosphorus and potash from the soil making it available for your plants. Lime is not actually a fertilizer, but it will help make acid soils more fertile, as well as more neutral in pH.

Of the products available, do not choose quicklime, which will burn and kill plants. Hydrate of lime is safe enough applied according to directions, but it is so fine that rain carries it away from root-level in the soil too quickly for plants to benefit from it. The best choice, ground dolomitic limestone, is sandy to the touch and dissolves slowly.

Dolomitic limestone should be available in any agriculture or garden store. Unlike faster forms of lime, it contains magnesium, a trace element plants need to grow strong. The recommended application for dolomitic limestone is 70 pounds per 1,000 square feet. Add it in the fall or early spring immediately after you have turned the soil, well before planting time. Its important to spread the limestone evenly because it stays where you put it in the soil.

Because it dissolves slowly, ground limestone should be applied only every two or three years once you have the soil in condition.

Increasingly, garden experts urge you to test the soil before adding lime to it. Garden writer Jack Kramer, in his book The Everest House Complete Book of Gardening, warns against routine heavy liming without soil tests because once too much lime builds up in the soil, you cant take it out. He says in New England compulsive liming has changed the natural acidity of soils, ruining some soils in the process.

To emphasize the point: you should test the soil every year as you start gardening. It may take a couple of years to get the pH properly adjusted, but once adjusted more lime may be unnecessary.

Neutral soil has a pH of 7; fractions above 7 indicate alkaline soils, fractions below 7 indicate acidic soils. For most plants anything in the range from 6 to 8 will be acceptable. Garden vegetables, annuals, grass, and many shrubs prefer a slightly acid soil dipping toward 6. A few plants, such as rosemary, lavender, and clematis appreciate extra lime.