Most indoor houseplants hail from the tropics. These evergreen plants usually thrive in the low-light conditions found throughout the home as they naturally grow under tropical forest canopies. One of the primary challenges with growing tropical houseplants is keeping the roots at the proper moisture without drowning them. Conditions in the home are much drier than the plant's natural habitat, so providing the right potting soil is vital to retain the necessary moisture without drying out too quickly.
Combine one part potting soil and one part peat moss together. Use purchased, sterile potting soil or reuse soil from your garden. Remove any roots or nondecomposed organic matter from the garden soil prior to mixing.
Place the soil and peat moss into a disposable roasting pan if you are using garden soil. Sprinkle water on the soil to moisten it, then bake at 180 degrees F for 1 hour. This kills any weed seeds or disease organisms present in the soil.
Mix 1 part perlite in with the soil and peat moss. Peat moss provides organic matter and helps retain moisture, while perlite prevents the soil from becoming overly damp.
Fertilize the soil prior to planting. Mix 2 oz. agricultural limestone and 3 tbsp. 6-6-6 analysis fertilizer to every 4 gallons of potting mix. Add 2 oz. superphosphate fertilizer if you are growing flowering tropical plants.