KC Gardens

Topsoil vs. potting mix: Choosing the right soil for your plants

Want to plant a garden but aren’t trying to rip up your whole yard at once? Try this strategy

Learn a simple, add-as-you-go strategy for building a backyard oasis.
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Learn a simple, add-as-you-go strategy for building a backyard oasis.

Soil is the basis of all gardening. Growing healthy plants always starts with good soil for strong root development.

All soils are not created equal. They have different components, and success depends on making sure you have the right variety.

Soil is not dirt. Soil is what plants grow in. Dirt is what collects on the furniture or under your nails. Soil is simply a mixture of sand, silt and organic matter that supports plant growth. In the gardening world, various mixes have been engineered to achieve greater success. This is where we get down and dirty to fully understand soils.

Topsoil

Topsoil is the natural layer that has formed at the surface over millions of years from rock decomposition, wind and water movement.

Topsoil in the Kansas City area is mainly heavy clay soil, which, while nutritious, doesn’t always have the ideal properties for growing healthy plants. It can hold excess moisture during rainy periods or be brick hard during droughts, affecting root development.

For practical purposes, topsoil is what you already have in your yard.

Enriched topsoil

Enriched topsoil is a mix of local topsoil and organic matter. The organic matter improves the quality of soil for better growth.

Here is the important point: If you are filling a low spot and don’t need better quality than what’s already there, purchase topsoil. But if you want to grow plants, go with the enriched topsoil. It’s superior to topsoil.

Potting (soil-less) mix

Potting mix is used in container gardening. The best quality potting soils do not contain soil (dirt); they are called soil because we grow plants in the material. Potting or soil-less mix is actually a mixture of peat moss, pine bark and organic materials. It is specially blended to have the right mix of air- and water-holding pores to promote good growth.

Adding topsoil or enriched topsoil to a container creates a heavy mix that often lacks proper drainage because of the clay. The formulated particle balance of a soil-less mix is ideal when used in small volumes because it provides the best environment for good root development.

Unfortunately, these mixes tend to be more expensive than topsoil. Potting soil comes in bags at the garden center right alongside the less costly topsoil or enriched topsoil. Remember your purpose when purchasing soil. If you are filling a hole, purchase topsoil. If you are improving your local soil or a bed, purchase enriched topsoil or compost. Select potting mix when planting a container garden.

Once you know the inside dirt on soil, you will avoid costly mistakes and be on the path to success.

Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Got a question for him or other university extension experts? Email them to garden.help@jocogov.org or visit KCGardens.KansasCity.com

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