You’ll find a variety of bags labeled as planting mix, potting mix, container mix and more. Check the label to see what the bag contains and recommendations for its use. Look for mixes, we’ll refer to as potting mixes, blended for growing indoor, ornamental and edible plants in containers. They are a mix of organic and inorganic materials that retain moisture while draining well. Some mixes include sand and mineral soil while many are labeled as “soilless.” These lightweight mixes consist of peat moss, sphagnum moss and compost for moisture retention, vermiculite or perlite for drainage but do not contain mineral soils such as sand or clay.
Potting mixes may be modified to accommodate the needs of certain plants. Orchid mixes often contain more bark for better aeration, cacti and succulent mixes have more sand or perlite for better drainage and African violet potting mix contains more organic matter to create a moist, rich growing medium.
Organic potting mixes are also available if you prefer to know the ingredients are free of pesticides and other contaminants. Check for the word organic and OMRI listed on the bag.
Potting mixes may or may not be sterilized to kill weed seeds and pests. If it doesn’t say sterilized, it probably isn’t.
As you narrow down your choices, continue checking the label for more details. Potting mixes often contain a “starter charge” of fertilizer. This minimal amount of fertilizer is usually gone after two or three waterings. Some include additional fertilizer that provides small amounts of nutrients over a longer period of time. The label may say controlled-release, time-release or slow release fertilizer, providing nutrients for the allotment of time specified.
Natural or synthetic wetting agents are often included to reduce the surface tension of water, so it’s better able to penetrate and evenly moisten the potting mix. Organic mixes often use yucca extract as a wetting agent.
Potting mixes should be light, fluffy and moist. Avoid bags that are waterlogged and heavy. The mix can break down, become compacted and some of the slow release fertilizer may be pre-released and damage young seedlings when saturated with water.
Moisten the potting mix with warm water before potting your plants. This helps ensure even moisture throughout. If the potting mix becomes overly dry, you may need to do a bit more work to rewet all the mix in the container. Set the pot in a container of warm water and wait for the potting mix to rehydrate. Or water thoroughly, wait 20 minutes and water again. Repeat until you achieve success.
Take the time to do a bit of research before buying your next bag of potting mix. Your efforts will be rewarded with healthy plants, beautiful blooms and a bountiful harvest from your indoor and outdoor potted plants.
Melinda Myers has written numerous books, including Small Space Gardening. She hosts The Great Courses “How to Grow Anything” DVD series and the nationally-syndicated Melinda’s Garden Moment TV & radio program. Myers is a columnist and contributing editor for Birds & Blooms magazine.