Growing media is any material that supports plant roots. It may look like a traditional soil or it could be hydroponic. To successfully grow plants, the medium must have the ability to hold moisture and air particles making osmosis possible.
Peatmoss is a light fibrous material that holds moisture. If allowed to dry, it becomes hard and takes time for water to penetrate. It contains little if any nutrients and is often considered a limited resource.
Ground wood particles are used in some growing mixtures instead of peat moss. The ground particles hold moisture but it can tie up the nitrogen in the soil as they continue to decompose. Companies using wood particles often add nitrogen to the growing medium to offset this problem. Anytime a nutrient is added to the soil it is listed on the bag.
Mineral soil, top soil, contains nutrients that are readily available to plants when mixed with organic matter. Mineral soil is costly to process as it needs to be sterilized to control natural pathogens that can destroy greenhouse crops. Mineral soil is rarely sold in soil mixes as it is heavy and costly to ship.
Perlite is heated lava turning it into small glass beads that when added to other fibrous materials it increases the growing medium’s ability to hold air.
Vermiculite is exploded mica rock. It, like perlite, is used to improve the soil’s ability to hold air and move excess moisture out the bottom of the pot.
Rice hulls are added to soil to improve aeration. It is common to find the hulls in growing mediums that are manufactured in areas when rice hulls are a by-product of rice production.
Sand can be used to increase drainage air in soils. To work it must be a medium coarse sand. Fine sand tends to plug existing holes, not make new ones. Sand does not contain nutrients but is easily sterilized with heat.
Companies that manufacture growing mediums have done research to develop their own soilless mixes that they sell as a specific or broad growing mixture.
The basic potting mixture will contain either peat moss or decomposing, ground wood with some perlite or vermiculite to improve drainage.
A seed starting mixture will be sterilized, have fine texture making it easy for seeds to germinate and water to percolate through.
Cacti mix is a coarse mixture allowing the water to drain quickly from the soil. People that tend to overwater plants might want to use this mixture with tropical plants too.
African violet mixtures contain more vermiculite and perlite than average tropical soils ensuring that the water flows through the soil as opposed to keeping to too moist.
Orchid mix is a coarse mixture that retains little moisture. It is usually composed of bark with some sphagnum moss.
Every company sells a growing medium that is slightly different from the competitions. How well they work often depends on how people water. If one doesn’t work well, try another.
Linda Tomlinson has gardened in Central Alberta for over 30 years. She can be reached at firstname.lastname@example.org.