But not only is dirt not soil, but soil is not always the same soil. Wonderful well-drained garden soil takes on a whole new personality once it is placed in a pot. The shorter the pot, the less well drained the soil will be. Even some commercial potting soil mixes do not provide the proper amount of drainage and water retention. If the mix contains predominantly soil, than add soil amendments.
Many recipes are available.
The taller the container the more natural drainage it provides. Garden soil should be pasteurized. Spread moist soil on a cookie tray and bake at 180 degrees F for 30 minutes. Peat Moss or coco fiber - Peat moss is partially decomposed sphagnum moss. When purchasing peat moss, look for sphagnum peat moss.