Potting Soil vs Topsoil – Differences + Which to use for Grass

Potting soil and topsoil are popular types of dirt in gardening. The two are different in composition, application, and nutrient sustainability. So, which one is better for grass?

Potting soil is a mixture of dirt, peat moss, organic matter, and nutrients important for container gardening. On the other hand, topsoil is naturally formed through the slow weathering of rocks and decaying organic matter over a long period of time.

Here is a summary of the differences between potting soil and topsoil.

Potting SoilTopsoil
Consist of various amendment materials like peat moss, fertilizer, and perlite, commercially mixed to meet various plant needs.Naturally formed through weathering of rocks and decomposition of organic matter.
It can be soilless with amendment materials like peat moss, perlite, and fertilizer.It may contain clay, sand, and compost manure, making it very rich in nutrients.
It doesn’t last longer when storedIt can last many years when stored
Usually light and fluffyTypically heavy due to sand or clay composition
Mainly used as a growth media for indoor container plantsCommonly used for topdressing, levelling, and fixing erosion damages in lawns and gardens

Potting soil vs Topsoil – Detailed Comparisons

In detail, the following are key differences between potting soil and topsoil:

1. Composition

Composition is among the main differences between potting soil and topsoil. Potting soil can be soilless or contain soil. It’s commercially manufactured to meet certain plant requirements. It usually contains various ingredients.

Potting soil may contain true garden soil, amendment materials like peat moss or coconut coir, organic matter like composted sawdust, fertilizer, and other materials like perlite or vermiculite to improve drainage. The ingredients vary depending on the purpose of the soil.

On the other hand, topsoil is made up of natural garden soil that is rich in different nutrients. It may contain clay or sandy soil, compost manure, and other decaying organic matter. These ingredients may vary depending on your region’s soil formation and climatic conditions.

2. Application

Potting soil that contains soil is ideal for growing plants outdoors, either in large pots or raised beds. On the other hand, soilless potting soil is better for indoor plants like ferns or cacti. It’s well-aerated and drained to support the healthy growth of your plants.

Topsoil is more of a soil conditioner than a growing medium for plants. It’s usually used to improve flower bed soil, topdressing lawns, enrich the existing garden soil, increase the volume of raised bed soil, and fill dirt or other debris when starting a new garden.

If you intend to use topsoil when starting a new lawn or for vegetable cultivation, you should mix it thoroughly with the native soil to improve aeration, drainage, and nutritional content.

Topsoil is not an ideal growing medium due to its poor structure. It has poor drainage that can lead to excessive water retention and poor root development. Clay or sandy topsoil requires some amendments, such as organic matter, to support the growth of plants

3. Longevity

Longevity also differentiates between potting soil and topsoil. Unopened bags of potting soil can last for only six months. Storing it for more than this duration will degrade its quality.

Potting soil in containers will start to degrade after two years. It’s. Therefore, it’s ideal for replacing potting soil in pots or containers after one or two years.

The quality of ingredients used for making potting soil will start to degrade in two years’ time. For instance, peat moss in potting soil will decompose fully within a period of two years. Therefore, it’s best to refresh the old potting soil in containers with 50% fresh potting soil.

Topsoil lasts longer than potting soil. Bagged topsoil can last up to 8 years when stored properly. However, it requires some amendments before use. Adding fertilizer or compost will help to improve drainage and its nutritional content.

4. Characteristics

True potting soil is soilless, light, and fluffy. It provides suitable growth conditions for container gardening. It has soil amendments to improve drainage, aeration, and nutritional value. Potting soil is sterilized during production and does not contain bacteria, fungi, or weed seeds that may attack your plants in their initial growth stage.

Topsoil is coarse and heavy due to clay, sand particles, composted organic matter, and other materials. It also contains soil microbes that are beneficial to your plants. Although topsoil is fertile, it’s poor drainage and aeration can prevent the healthy growth of plants when not amended.

Will Grass Grow in Potting Soil?

Yes, grass can grow in potting soil. However, it is not ideal for outdoor plants such as grass. Potting soil is best when intending to grow your plants in containers. It is best for planters, hanging baskets, window boxes, and other containers where drainage and weight may be a problem.

Potting soil is ideal for plants that require well-drained and aerated soil. It allows excess water to drain out from the bottom of containers through gravity. It pulls in air to replace the drained water. Plants breathe through roots, and they require a well-aerated growing medium.

Between Potting and Topsoil, which is good for the grass

Topsoil would be the best choice over potting soil when starting a new lawn. Topsoil provides a deep root development medium for natural lawn grass. It also provides healthy germination and growth of grass.

If your garden soil is not working for your grass due to the overuse of fertilizers or compaction, you may be required to buy topsoil. Put the topsoil in your garden and conduct a soil test to determine if other amendments are needed.

You may need to add organic matter like compost to improve drainage and aeration. It’s also important to adjust the pH. Incorporating your existing garden soil with a few inches of topsoil will give your grass a better chance of establishing roots properly and growing healthy.

Topsoil is also much cheaper since it’s sold in bulk and can be used in different ways before planting your grass. For instance, you can use it to level your lawn by filling old ponds and repairing cracks in your yard after a heavy rainstorm-related erosion.


  1. University of Maryland Extension: Growing Media (Potting Soil) for Containers
  2. University of Illinois Extension: Using Soil and Soil Mixes
  3. University of Massachusetts Amherst: Bagged Potting Mixes and Garden Soils for Home Gardeners

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