Choosing the best soil for outdoor plants or for potted plants is critical since the health of your plants depend on the nutrients it can get from the soil. While you might think you can use either potting soil or topsoil for potted plants, there are significant benefits to potting soil that topsoil can't offer.
Difference Between Potting Soil and Topsoil
Potting soil and topsoil are made from very different materials. Potting soil is usually composed of bark, compost, moss, perlite and vermiculite. In fact, it doesn't have any actual dirt in it at all. That's because dirt can contain fungi and other elements that can damage potted plants.
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Potting soil or potting mix can be rather pricey, especially in comparison to topsoil. That's because topsoil is naturally occuring. It's exactly what it sounds like: simply plain dirt taken from the surface of the earth. It has no added nutritive ingredients that plants need to thrive.
Using Topsoil for Potted Plants
You certainly can use topsoil for potted plants, but that doesn't mean you should. If you do, your plant probably won't get the nutrients it needs, won't grow at the rate you expect and will be likely to die sooner. The best topsoil for vegetable gardens may not be topsoil at all.
This is because, when a plant is in a pot, its root systems don't have the opportunity to branch out and seek the nutrients they need. That means you're responsible for giving those nutrients to the plant. Even if you water precisely according to the plant's specifications, its growth may be disappointing if you have used only topsoil when planting. That's also the reason why potting soil is so much more expensive. It takes a wide range of ingredients, testing and processing to infuse the packaged planting medium with everything your infant plants need.
You may also be wondering about gardening soil, which is compost that has been enriched with compost and other beneficial organic matter. However, gardening soil is meant to be used outside in a garden. It certainly has more of the essential elements for plant growth, and much more of these than topsoil. However, manufacturers make garden soil based on the understanding that customers will use it outdoors, where animals, weather and the ground itself can infuse it with nutrients. Your potted plants will do better with garden soil than with topsoil, but they'll perform best with potting soil.
When Should You Use Topsoil?
If you shouldn't use topsoil for potted plants, then what is topsoil good for? It does have some important uses. Use it to fill a hole in your lawn or yard, or as the top layer of your garden if you run out of gardening soil. You can also mix it with gardening soil to cut costs, as long as you have at least equal parts gardening soil and topsoil.
A handy rule of thumb is to use potting soil for potted plants, including when propagating plants in pots. Use garden soil in outdoor gardens, especially in garden beds. Use topsoil to fill holes or mix it with gardening soil for outdoor plants.