Evaluating Your Soil

Most perennials do best in a rich, well-drained soil. It makes sense to modify the soil in a new perennial bed before planting. Unlike your vegetable and annual beds, you won’t be tilling your perennial bed each year, so you won’t be able to add organic matter or other amendments as easily as you do to those gardens. You may want to test your soil’s nutrient and pH levels early in the process. That way, if specific nutrients are called for, or you need to add lime or sulfur to adjust pH, you can incorporate these right into the soil.

What type of soil do you have?
Soils can be categorized by the size of the particles they contain. Ideally, a soil will contain a range of mineral particle sizes -- from microscopic clays to relatively large grains of sand. These particles are bound together into groupings of various sizes called aggregates. Soil composed of these aggregates has lots of pore spaces of various sizes, and these spaces contain water and air, both of which are important to plant roots. The term loamy is used to describe a soil with these desirable characteristics.

Clayey soils contain mostly microscopic particles. With few pore spaces, these soils tend to become waterlogged. Clay soils can become compacted by heavy rains or foot traffic and, when dry, the hard surface may crack. Clay does, however, contain many nutrients.

Sandy soils contain relatively large particles. Unlike clay soils, very sandy soils have excellent drainage, but can drain so quickly that plants suffer from drought. Sandy soils are very low in nutrients.

Here are two ways to get a feel for the composition of your soil:

1. Squeeze Test. Take a handful of moist soil. Compress it into a ball, then press it between your thumb and index finger and try to form a ribbon. If the soil is crumbly and won�t form a ball, it probably contains a lot of sand. The stickier the soil is, and the longer the ribbon you can form, the more clay the soil contains. Loamy soil will form a ball that crumbles when poked.

2. Soil Shake. Fill a large glass jar about two thirds full of water, then add enough soil to almost fill the jar. Shake the jar vigorously, then let it settle for a few days. The larger particles -- gravel and sand -- will settle first, followed by silt-sized particles, and, finally, microscopic clay particles. In fact, the clay may stay suspended in the water for quite some time. Organic matter will float at or just below the surface of the water. By looking at the layers, you can find the approximate ratio of sand to silt to clay in your soil. "Ideal" loamy garden soil contains 40% sand, 40% silt, and 20% clay.

sandy, loamy, and clayey soils

Sandy soils dry out quickly, and have low nutrient levels. Clayey soils retain moisture, but can become waterlogged. Loamy soils are ideal for perennial gardens, because they retain adequate moisture, yet drain well.

If you don't have ideal soil, don't despair. In the next few pages we'll talk about ways to improve soils.

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