How to Make Potting Soil. Many avid gardeners make their own potting soil to ensure a proper mixture of ingredients and to save money. Those new to gardening often make the mistake of using garden soil in plant containers. Although some elements of outdoor soil can benefit potted plants, potting soil must contain ingredients that promote nutrient absorption and water retention. Homemade potting soil is easy to mix and promotes health in most plant types
Buy horticultural vermiculite at a garden or home improvement store. Vermiculite is a common ingredient in potting soil because it significantly improves aeration. The mineral also promotes moisture retention which results in better absorption of nutrients and healthier plant growth. Horticultural vermiculite is non-toxic, sterile and odorless.
Purchase shredded peat moss. Peat moss is harvested from bogs full of decomposed sphagnum moss. Adding shredded peat to all-purpose potting soil promotes a healthy combination of water and air in soil and softens soil texture, encouraging root growth. Peat moss lacks nutrients and dries out over time, so it's not ideal for planting unless mixed with other ingredients.
Get superphosphate. This synthetic fertilizer contains phosphate, the form of phosphorous beneficial to plants. Superphosphate gradually decomposes in soil, providing plants with essential nutrients. Flowering plants respond especially well to superphosphate additives.
Find limestone dust. If you live in area rich with limestone, you may be able to get the dust from local quarries. You also can find it at large garden centers. The calcium carbonate in limestone has acidic properties that complement alkaline soil ingredients, resulting in pH balance.
Look for 5-10-15 soluble fertilizer. This water-soluble fertilizer is 5 percent nitrogen, 10 percent phosphorous and 15 percent potassium. Plants cannot thrive in soil that lacks the proper balance of these three essential nutrients.
Measure ingredients before mixing in a large plastic container suitable for soil storage. To ensure safety, wear gloves and protective eyewear when making potting soil.