Using unpasteurized or regular soil from the garden to grow potted plants can cause problems, as garden soil can lack the ability to drain properly and contain disease pathogens and weed seeds. To avoid these problems and save money, you can make your own pasteurized potting soil from easy-to-obtain ingredients.
Pasteurize garden soil to kill pathogens by placing damp soil in a turkey roasting bag then putting the soil-filled bag in a roasting pan. Make a hole so that you can fit a meat thermometer into the bag to check the soil temperature. The soil is dampened to create steam for the pasteurizing process. Set the oven to 200 degrees F and bake the soil at 160 to 170 degrees F for 30 minutes. The temperature must be at least 160 degrees F for 30 minutes, so adjust time accordingly if temperature drops below 160 degrees F. Don't allow temperatures to get over 175 degrees F.
Use compost that is well composted. Good compost has the look and consistency of damp soil, and the plant matter used to make the compost is unrecognizable. It should have little or no smell.
Perlite is made from a volcanic rock and helps soil hold water without becoming soggy. It is available at large garden centers or department stores that have larger garden sections. It is lightweight, inexpensive and easy to use.