If you’ve ever gone to the garden store to buy bagged potting soil, you’ve probably encountered more choices than you expected. Which one of these is the right one? I have asked myself this question more than once.

Chances are you have too. Shaun Broderick, ornamental horticulture specialist with the Mississippi State University Extension Service and researcher with the Mississippi Agricultural and Forestry Experiment Station, says understanding which potting soil you need can be confusing. 

He shared his expertise on the different types of potting soil along with a few tips with us below.

Potting soil usually does not contain any actual mineral soil. It’s a soilless mix that is often peat-based, though coconut coir is becoming a little more common. Many brands today are charged, or have fertilizer mixed in them, especially slow-release fertilizers. The amount of fertilizer varies per brand. 

Pro tip: Try to find potting media without fertilizer. That gives you complete control of how much and what type of fertilizer you can use. Plus, if the potting soil has been sitting on a pallet in the weather for a while, microbial activity and ammonia volatilization can reduce the amount of nitrogen those products can provide to the plants. So, if you are going to buy potting soils with fertilizer in them, try to get the products fresh and use them up, or plan to add some fertilizer to supplement.

Seedling mix is screened potting soil in which larger sticks are sifted out. Sometimes vermiculite is added to increase its moisture-holding capacity. I usually just use potting soil and remove the large sticks. This is what many nurseries do as well.

Pro tip: Avoid broken bags. There’s a greater chance that fungus gnats found a home in broken potting soil bags. You can treat for fungus gnats with a larvicide specifically for gnats, such as Gnatrol, but this is an extra step you might be able to skip if you don’t have them in the potting soil to begin with. When using larvicide, always read and follow the label directions.

Raised beds: These are beds that are above the soil surface. They can be made by simply pulling tilled soil into a mound. Gardeners typically have the most success gardening in raised beds. Sometimes gardeners will add side walls to the beds and fill them with soil completely different from what they have. Most bagged raised-bed garden mixes on the market today are also soilless and are made from aged bark rather than peat moss. This makes them cheaper to transport because they are lighter. Usually, if it’s labeled as a “raised bed” mix, that means you do not need to incorporate it with native soil. The advantage of these products is that they usually do not contain weed seeds and drain well. However, you may need to water them more than the actual soil. These products can be used to grow flowers as well. 

Bagged garden soil is often a soil amendment and is not designed to be planted in directly. Instead, it is designed to be mixed into existing topsoil. This will improve drainage of native soil, help the plants absorb nutrients more efficiently, and increase soil microbial activity. These products can be used in flower beds as well. 

Outside of these prepared mixes, there are composts, vermicomposts, and aged manures. These are fantastic for improving soil and plant health. Mixes usually have some form of these in their formula.

How to measure product quality

As far as products go, there are a lot of differences in quality out there. The best method to determine product quality is to grow plants in each one you select. This will likely be trial and error for home gardeners. At our nursery, we would trial plants side by side in different potting mixes until we found a good brand that worked for our crops in our environment. 

Price is not necessarily a good way to determine if a product is good quality or not. The quality of national brands could vary based on where they were formulated and how long they have been sitting around. If you want organic products, just make sure the label says “organic.” 

A word of advice: Be careful of guidance from social media personalities. I saw a YouTube video of a popular gardening personality who was advising people on whether to buy different composts based on the way they smelled. This is a terrible way to measure a product’s quality.

Buy in bulk

Outside of bagged products, nurseries also sell these products in bulk, except for the potting soil. It is often much cheaper to go that route than to buy bagged products if you have access to a truck. There are some quality bulk products out there.

Happy growing!