DIY Potting Soil Mix

Potting soil mix provides an ideal growing medium for container gardening of all kinds. Though often called “potting soil”, the mixes you purchase at your landscape supply store do not contain soil at all. You should never use topsoil to fill your containers. Topsoil is too heavy, prone to compaction, and full of pests and diseases that can be passed on to your cuttings or houseplants. Instead, potting mixes are designed specifically to retain moisture and nutrients, allow drainage, and remain light and fluffy.

What Goes into Potting Soil Mix?

Potting mix typically contains some combination of:

• Sphagnum moss (commonly known as peat): Peat is used in almost all potting mixes because it adds bulk with little weight, and holds water extremely well.
• Perlite: Perlite is derived from volcanic ash and also holds water well. Its fairly large granules increase pore space and thus allow better aeration and drainage.
• Vermiculite: Vermiculite is a mineral that can be added instead of perlite. It functions in much the same way, but retains water and nutrients much better than perlite. However, it does not aerate soil as well as perlite, so it is best used in potting mixes for water-loving plants.
• Sand: Sand increases porosity and drainage in the potting mix, and is great to use a little extra in mixes designed for cacti and succulents.
• Limestone: Limestone contains calcium, which neutralizes the pH caused from peat moss’ acidity.
• Fertilizer base (often compost): Fertilizer supplies the necessary nutrients to help your plants grow well. Pre-mixed granular fertilizer or bone meal work well, in addition to compost.

When mixing your own potting soil at home, you can alter the formula to produce different textures, densities, and nutrient levels to suit the plants you are growing.

How to Make Your Own Mix

Different plants need different potting mixes to meet their specific growing requirements. A general mix works well in most cases for growing flowers and vegetables, but you will need to alter this mix in other situations.
Start with this general, all-purpose recipe for potting mix. From this general formula, you can adjust the proportions to best suit your growing goals.

• 40% peat moss or coir fiber
• 40% perlite or vermiculite
• 20% compost
• ½ tbsp lime per gallon of peat moss
• 1.5 tbsp of any granular, complete fertilizer per gallon of total mix

When starting plants from seed or propagation: Mixes that are fluffier and more fine-textured work best. Omit the compost from the mix, as it is heavy and dense, and instead replace it with sand. The sand will help increase drainage and porosity, and keep the potting mix airy.

For cacti, succulents: A base mixture of ⅓ peat moss, ⅓ mix of equal parts perlite and vermiculite, and ⅓ sand with the appropriate lime treatment will allow succulents to get proper moisture, nutrients, and drainage.

For potted shrubs and trees: Mix equal parts peat moss, sand, compost, and perlite together with the appropriate amount of lime and fertilizer to give your large potted plants an excellent growing medium.

Of course, many weekend gardeners and homeowners may not want to go through all the trial and error of making their own potting soil mix. This is when Big Earth Landscape Supply can come to the rescue. We offer quality potting soil for both commercial and residential use. Have questions? Stop by or give us a call.