Healthy soil equals healthy plants |

Healthy soil equals healthy plants

Faced with the daunting task of creating a garden in foothill soil, many newcomers opt for quick results, and order a load of topsoil with a plan to build up rather than dig into the clay.

Unfortunately, that topsoil is rarely native topsoil, a mix of clay and humus. If it has sand or silt in it, the amendment should not be mixed with the existing clay soil.

Used in raised beds or planters, the topsoil allows for easy digging, but it will not hold moisture. In our hot and dry summer, more frequent irrigation is not to the advantage of the garden or the gardener.

When I began my first foothill garden, I soon discovered that the soil was not unlike that in which my great-aunt Jess had grown her vegetables, fruits and flowers in the hills southwest of Sebastopol in Sonoma County. My parents’ home was just three miles away, but the soil was entirely different.

We gardened in sandy loam, where a shovel slipped easily into the unimproved ground, and weeds were easy to pull. No wonder I started gardening when I was very young!

That summer in 1977, a newcomer to Nevada County, I thought often of my aunt Jess as I dug the clay soil and amended a small area for my vegetable garden. Fortunately, I had been gardening for years, and knew that my goal was a loose soil, rich in nutrients and active with earthworms. I needed lots of organic material.

Cover cropping quickly became my first choice of amendments. The roots of annual rye help break up the clay soil. Once clover, vetch, or rye has been dug into the soil as green manure, the worms appear to feast on the decomposing plant material, adding more soil improvement.

Buckwheat, a warm season annual, does well as a summer cover crop in clay soil. Its growth is rapid and succulent leaves break down quickly when the cover crop is dug into the soil.

Animal manures add essential organic material, and often nitrogen. Most are mixed with wood shavings or rice hulls. Mushroom compost may not be as high in nitrogen as the animal manures. It’s important to obtain certified organic compost when you’re using it in your vegetable garden. In the vegetable garden I incorporate three to four inches of compost into the beds each year.

Since they may be high in nitrogen at first, I water amendments as soon as they are delivered, and leave them to decompose for a few weeks. Remember that any pile of decomposing plant material can heat to the point that it will ignite.

Foothill soils are low in phosphorus, and generally acidic. The addition of organic phosphorus allows for good root growth and fruit production. Fifteen pounds per hundred square feet should be applied and incorporated into the soil where the roots will be able to reach it. At the same time, the addition of five pounds per hundred square feet of oystershell will adjust the soil pH to make nutrients more available.

Take another look at that clay soil so prevalent in the foothills. While difficult (or impossible!) to dig in when it dries out, the native soil is rich in nutrients and water- holding capability.

Once organic compost, phosphorus and oyster shell are added, our native soil is wonderful for gardening.


Carolyn Singer has gardened in Nevada County for 28 years. She is the owner of Foothill Cottage Gardens ( Send your garden questions and comments to

U.C. Master Gardeners classes

When Children Garden, Imagination Grows: a Plant Growing Workshop for Children; ages 4-8; Thursday, June 21; 10 a.m. to noon

Earth-Friendly Gardening Practices for the Sierra Foothills; Saturday, June 23; 10 a.m. to noon

Both workshops are at the Demonstration Garden, 1036 W. Main St. (NID grounds) in Grass Valley.

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