These are specially formulated for starting seeds indoors. Soilless mixes are sterile and reduce the risk of losing seedlings to damping off, a fatal soilborne disease. Using soil directly from the garden is not recommended, because it may contain insects, weed seeds, or disease organisms that could damage or kill the young transplants. If garden soil is to be used, combine it with equal parts of sand and peat moss to improve drainage and structure. A teaspoon of ground limestone per quart of mix should also be added to obtain the proper pH. The mix must then be pasteurized to eliminate pests by heating to 180oF for 30 minutes.
Heated soil gives off a strong smell, so consider doing it outdoors.
Getting Started Containers, pots, flats, etc., are another essential component for starting transplants. A lack of drainage can cause the soil to become saturated and can encourage root rot diseases in the transplants. Plants that are started too early become elongated, pale green, and weak. The goal is to produce a stocky, moderately sized plant that will recover quickly when it is planted outdoors. Table 3 lists how many weeks pass between seeding indoors and transplants are ready for planting in your garden.