Should you whip up a potting mix for your container flowers and vegetables? Sure! Not only will you be able to make custom mixes to support your particular plants, but you'll also save money along the way. "Mixing your own potting soil versus purchasing a premixed version may be more economical if you plan to [make] large numbers of pots on an annual basis," says Jeana Myers, a North Carolina State horticulture extension agent. If you've been thinking of creating your own mix, here are six things to know.
You can make many different kinds of potting mixes.
Which means that each plant can get a custom blend based on its particular needs. But finding a good ratio of moisture-holding, well-drained, and root-supporting materials can be tricky, explains Myers. "And you need to make sure the pH and fertility levels are appropriate for the plants you are growing," she adds. Lime usually needs to be included to bring the pH up to desired levels, and it can take several weeks, at a minimum, to do that.
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Every ingredient counts.
Basically, says Myers, you have to think about four basic functions for your potting mix and its components. "They must be light enough to allow roots to easily penetrate and to get the air they need, moist enough to get the water they need, solid enough to support the roots and plants, and contain enough nutrients at the proper pH to flourish and grow." Still need help? Ask for guidance at your local garden center. Or bookmark these popular materials and their functions:
- For lightness and root penetration: fine pine bark, perlite, and vermiculite
- To retain moisture: composted leaf mold or pine bark, coir (coconut fiber)
- To provide some density and support: compost, soil and sand
- For pH remediation: limestone
You need a basic recipe.
Myers likes this recipe, which works well for large plants: one part compost, one part fine pine bark, and one part sand, with lime (two tablespoons per five-gallon bucket) and fertilizer. "Slow-release fertilizers come in different concentrations," she says, "but a 10-10-10 would be applied at about a half cup per five-gallon bucket." Adjust for slow-growing plants, cacti, or others that have low fertility needs.
Rethink peat moss.
Peat moss has long been a favorite ingredient in potting mix for its ability to retain moisture and oxygen without becoming heavy. But now some gardeners are rejecting peat-moss-based mixes due to the fact that harvesting and using peat moss releases carbon dioxide, the major greenhouse gas causing climate change. Instead of peat moss, try composted leaf mold, pine bark, or coir to retain moisture in the mix.
You'll need the right equipment.
Martha suggests mixing the ingredients in a plastic garbage pail or galvanized bucket that's large enough to allow you to really incorporate everything. You'll also want a large storage container to house the final mixture. Since mixing ingredients involves lots of dusty products, wear a mask so you're not breathing in any particles. Another necessity: gardening gloves.
Hydration is crucial.
"Once a mix has been created, it will keep indefinitely," says Myers, "especially if kept only slightly moist as opposed to wet, which would dissolve the slow-release fertilizers."