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What
is potting soil?
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If you’ve
ever bought a bag of potting soil, you may have been astounded
to see it labeled “soilless.” Huh? If it’s not
soil, what is it?
Most potting soils are made up largely of peat moss, bark, and perlite. (Perlite looks like tiny white pellets; it’s actually heat-puffed volcanic glass, included to keep the mixture from being too dense.) Often, potting soils are sterilized by steam to kill potentially disease-causing microorganisms. So potting soil isn’t really soil, because it lacks both minerals and humus. Lifeless and devoid of minerals, potting soils “do no harm” but generally deliver few nutrients. You’ll want to fertilize early and often if growing plants in potting soil. Actually, “soilless” potting soil helps make an interesting point: You don’t really need soil to grow plants. Hydroponic gardeners grow plants using only nutrient-rich water. In place of soil, inert substrates such as perlite or rock wool may be used to provide aeration and structural support for roots.
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