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Learn how to make your own soilless potting mix at home! Commercial bags are pricey, really add up in costs, and also vary greatly in quality, leading to fried plants. It’s satisfying to make your own to give your plants a healthy start—and leads to fewer headaches. Here’s our basic DIY potting mix recipe.
Containers are great for a number of reasons, namely that they’re versatile, space-saving, and allow you to be more efficient in your use of resources. If you have a small garden space or live in an apartment with a balcony or rooftop, containers are for you.
What is Potting Mix?
For containers, you’ll often read that you need to buy or make a good potting mix. But what does this mean?
Potting mix is not garden soil—which is heavy and includes sand, clay, and other cheaper additives that won’t work for containers. Some people may refer to it as potting soil, but rather, potting mix is “soilless.” It’s lighter and fluffier than ground soil to allow enough air and water for the roots for healthy root growth but also provides enough anchorage for roots. These soilless are sterile, so there is no chance of introducing pest or disease problems.
Potting mix can certainly be bought in bags at garden stores. Look for “Soilless Potting Mix,” which generally includes three ingredients: 1) peat moss or coconut coir for moisture and nutrient retention, 2) pine bark for anchorage, and 3) either perlite or vermiculite so air space so it’s light and fluffy. Some potting mix also includes fertilizer or moisture-retaining treatments. If you use a potting mix with fertilizer, you’ll need to adjust the fertilizer you provide. (Think of salted butter versus unsalted butter in a recipe!)
But many gardeners who plant a LOT of containers or raised beds or start seeds indoors will mix up their own potting mixes! For the number of containers I use in my garden, I learned long ago that it’s much cheaper to make my own potting mix and store it in an old trash can rather than pay for several big sacks of pre-made potting mix. Plus, I can customize the mix for a variety of different plants.
Before Making Your Own Potting Mix
Before we go any further, note that if you only need a few small containers’ worth of potting mix, you may actually be better off buying a pre-made mix! Making your own is usually only economical on a large scale or in the long term. Here are a few things to keep in mind before creating your own mix:
When it comes to any potting mix, the lighter it is, the better. Loose and porous mixtures not only make a container lighter to move, but they also transport water, fertilizer, and air to plant roots more quickly and allow for good drainage, which is important for container gardening.
Start with the basic recipe below and then add soil sulfur to lower the pH or lime to raise the pH, according to the needs of your plants. Both additives can typically be found at garden centers. Plants such as lettuce, Russian sage, and marigolds prefer sweet soil with a pH of about 7.5, while others are acid lovers, like ferns, asters, and strawberries. They need a pH of about 5.5 to 6.0. Here’s a list of more plants’ pH preferences.
If rapid drainage is needed, as is the case for cacti, succulents, and lavender, add extra sand and perlite.
If greater moisture retention is needed, as is the case for ferns and woodland flowers (like primrose) add extra vermiculite or coconut coir.
My Basic Container Potting Mix Recipe
1 bucket (10 quarts) coconut coir
1/2 bucket (5 quarts) perlite
1/2 bucket (5 quarts) vermiculite
1/2 bucket (5 quarts) screened compost or composted cow manure
2 cups fine sand
2 cups pelleted time-release fertilizer
Instructions Mix thoroughly. It makes enough to fill two 14-inch tubs or five 12-inch hanging baskets—double or triple the recipe for bigger containers.
How Much Potting Mix Do I Need?
Potting mix is sold by volume (typically measured in quarts), and most pots are measured by their diameter. To translate quarts of mix into various pot sizes, use this quick reference.