What’s the Difference? Garden Soil vs. Potting Soil
Learn which of these garden store staples will provide the best environment for plants to thrive in your garden.
If you’re planning a new garden, you should start with good soil. After all, soil is the medium of life for plants, providing a place for roots to spread out and take up water and nutrients. At the garden center, you’ll typically see two bagged options: garden soil and potting soil. Both products are made from quality organic materials. Both products promise to grow strong, healthy plant roots and help you use less water. Yet, while garden soil and potting soil each provide plants with excellent growing conditions, they are not interchangeable.
Garden soil and potting soil are formulated for different applications. Garden soil is an amendment that is mixed with native soil, while potting soil is used alone for container gardens like potted houseplants and window boxes. Choosing the wrong one can lead to problems like moisture buildup and soil compaction, which cause root damage and inhibit plant growth. Ahead, we compare the two options—garden soil vs. potting soil—to help you select the material that enables your plants to thrive.
Bagged soils consist of different ingredients for different purposes.
Garden soil is made of natural topsoil or sand blended with relatively inexpensive, bulky organic material. Ingredients like composted bark from mill operations, used mushroom compost, and composted cow or chicken manure are commonly blended into garden soil mixes. The coarse organic matter in garden soil improves the water holding capacity of sandy soils and loosens the texture of heavy clay soils for better root development in garden beds.
Meanwhile, potting soil mix contains no natural soil. It is a specially formulated mix made of peat moss, ground pine bark, and either perlite or vermiculite. This mixture is highly acidic, so limestone is added to balance the pH. A wetting agent is also added to keep the mix from drying out, because both peat moss and ground pine bark are difficult to wet once they have dried. Finally, potting soil includes a small amount of plant food. These ingredients make potting soil a perfect replacement for natural soil in container gardens.
Garden soil improves the texture of natural soil.
Most new gardens don’t have perfect growing conditions. Sandy soil dries out too quickly. Clay soil stays wet too long, but once dry it is difficult to moisten. The bulky organic material in garden soil is meant to be incorporated into the native soil in the garden bed to balance its water retention and drainage abilities, no matter the current texture. It helps sandy soil retain more moisture, and opens the texture of tight clay soil for better drainage.
Potting soil provides balanced moisture for container plants.
Potted plants also need just the right balance of moist, well-drained soil. Potting soil is formulated to be a completely balanced growing medium. The mixture of organic material and perlite or vermiculite allows both air and water to flow through the soil while retaining enough moisture to nourish the plant.
Use garden soil outdoors, in the ground.
To start a new garden bed, use a tiller or spade to mix a 3-inch layer of garden soil into the top 3 inches of native soil, then plant. If you are planting a single tree or shrub, mix garden soil in a 1:1 ratio with the native soil that you dig out of the hole, and use the mixture to backfill and firm in the new plant.
Use potting soil in indoor or outdoor container gardens.
Potting soil is for container plantings, indoors or out. Make sure your container has a drain hole in the bottom (and a saucer to protect your floor from water, if indoors). Cover the drain hole with a few small stones or a piece of mesh, to keep soil mix from falling out. Fill the container three-quarters of the way with potting soil, add seedlings or plants, and firm them in with more potting soil.
There are living components to garden soil but not potting soil.
Processed minimally, garden soil retains microbes that were in the original natural soil including bacteria, protozoa, fungi, actinomycetes, and nematodes, along with others leftover from composting. The mix of microbes includes some types that benefit plants by helping them take up nutrients and water from the soil. Most weed seeds and harmful microbes are eliminated from garden soil by the heat that is generated during composting. The few that may remain are vastly overshadowed by those existing in native soil.
Potting soil is sometimes called “soilless mix.” As such, it’s devoid of two components of true soil: minerals and microbes. Manufacturers of potting soil intentionally sterilize the mix with either heat or chemicals to eliminate any potentially harmful microbes and kill weed seeds. In the absence of beneficial microbes that assist plants with nutrient uptake, potting soil includes some plant food.
Prices can be misleading.
The price of potting soil per unit of volume is two to three times higher than garden soil, due to the higher level of processing of potting soil and different ingredients. At a nation-wide retailer like Lowes, a .75 cubic foot bag of garden soil costs $4.28, or $5.35 per cubic foot, while the same manufacturer’s potting soil in a 50 quart (1 cubic foot) bag costs $14.48.
Don’t let cost-cutting sway you from one soil to the other. For garden beds in the ground, you’ll always want to choose garden soil to build upon and improve the plot’s existing soil. Potting soil is the only choice for container gardens. Start with the right soil and you will lay a foundation for success in your garden.