With vegetables, fresh growing medium is important to avoid soil-borne diseases — just as crops should be rotated in a vegetable garden so that plants in the same family, such as tomatoes, peppers and eggplants, are not grown year after year in the same soil. It is best to completely change the growing medium in containers for each season unless you are going to plant vegetables from a completely different family, such as cabbages in a pot where tomatoes were previously planted. Of course, you should discard the growing medium if you had any problems with soil-borne diseases in the previous year.

If you are sowing vegetable or flower seeds, always use fresh, sterile growing medium because seedlings are especially delicate and vulnerable to disease.