Prepare Your Soil

Before you plant your new garden, understand your soil.
Healthy soil will help your plants get established and thrive.
Soil texture and organic content should all be taken into consideration in preparation of your new landscape.

Drainage is one of the most important characteristics of your garden’s soil. Soil needs to be porous enough to allow air and water to travel in between pore spaces and, ultimately, to the roots of the plants. Sandy soils tend to have good drainage, while clay soils have poor drainage.

Clay soils

Moist clay soil, when pressed into a ball, will hold together well and not crumble when dropped. There is little or no presence of grit or large coarse particles and you can form a long ribbon when pressed between your thumb and index finger.

Clay soils are made up of tiny, microscopic mineral particles packed closely together that leave little pore space for air. These poorly aerated soils absorb water slowly, and irrigation water may puddle or runoff. These soils have poor drainage (downward movement of water). Once wet, clay soils hold a lot of water but in a manner that locks the water away from plants.

Sandy soils

Moist sandy soil will form a cast but barely hold together, and will only form a short ribbon, if any, when pressed between the thumb and index finger; you can feel the coarse grit of the relatively large particles. Sandy soil is well aerated and drains well. Sandy soils absorb water quickly when irrigated. They hold little water and dry quickly. Because sandy soils are well drained, nutrients are lost from the soil more quickly than to clay, thus, requiring more frequent feeding and watering.

Loam soils

Moist loam soil will form a ball easily and will make a ribbon of approximately one inch or more. You may feel some grit from a small amount of sand particles that are present. A handful of loam forms a pliable ball that breaks apart with a gentle touch. Loam soils are easy to work with. Loam soils are an ideal balance between large and small mineral particles, giving loam soil the title of ideal garden soil. In this type of soil, no single soil particle predominates, hence offering a combination of large and small pore spaces. Loam soil drains well, and doesn’t dry out very quickly. Nutrients will be lost at a moderate rate. Watering frequency will also be moderate compared to sand.

You can change the texture of the soil in your garden, but it will require work. A less costly alternative is to amend your soil. You need to work with what you have, and make what you have work for you.

Ideal soil amendments

The ideal soil amendment for most situations is composted organic matter; it adds nutrients to the soil and increases the soil’s water-holding capacity. It encourages healthy populations of beneficial soil microorganisms. However, composed organic matter, if purchased, costs more than non-composted material (such as wood chips). You can learn more about composting through the City of San Diego's Composting Workshops.

Non-composted organic matter is also helpful, breaking up the soil and increasing its water-holding capacity. Soils and microorganisms need organic matter, and organic matter needs microbes for decomposition (composting).

In heavy clay soils, organic matter increases the porosity of the soil, making for better soil aeration. Inorganic amendments, such as gypsum and lime, also help loosen clay soil. In sandy soils, organic matter gets into the pore spaces to act like a sponge to hold water and nutrients. It’s a good idea to rototill the new garden area if this was not already done as part of the grass removal process. This helps work the amendments into the soil, by completely breaking up the soil about six inches deep.

Also visit Step 3 of A Homeowner's Guide to a WaterSmart Landscape for more information.