Sterile soil is not good for the plants
Luckily you can’t easily buy it
When sowing it is said that you should use potting soil because it is sterile. That is fortunately a tall tale. Mostly, sterile soil is not sold, it is too expensive and not at all useful.
Soil and sphagnum contain important microorganisms. Everyone knows that earthworms are beneficial in the soil. They chew dead plants in small pieces and out of it becomes what fertilizes the soil. Microorganisms are so small that you can’t see most of them. Microorganisms are beneficial fungi and very small animals. They are just as useful as the earthworms.
Beneficial fungi fight the fungi that are harmful for the plants.
Some pour boiling water in a bucket of soil to make it sterile. Others bakes it at 100 degrees. When they do that, they kill important animal and fungi life.
Potting soil is a fine and pure sphagnum. Sphagnum does not contain weed seeds, but there is still life in it. The most important thing is that the potting soil is as pure as possible. Sphagnum is pure. That’s why it makes good sense to use potting soil, but don’t make the soil sterile.
Potting soil is good for new seeds, that later will be transplanted, but it is not sterile, and it shouldn’t be.
Photo: Grøn Kommunikation
Om Lars Lund
Danish horticulturist and journalist
Lars Lund has for many years engaged in the garden and greenhouse. Lars has published many books about greenhouses, and he has participated in many Danish horticultural TV shows. He is a walking garden encyclopaedia, and he has answers for most basic cultivation questions – also the more ambitious ones.