Homemade Planting Mix

Soil-Based

• Soil-based potting mixtures were the original products available to the homeowner. Manufacturers sterilized garden soil with heat to kill off any weeds, bacteria or bugs that might be present. They add equal parts of builder's sand and sphagnum peat moss and the resulting mixture is ready for planting. This tends to be heavy, although not as dense as garden soil. This is a good mixture for houseplants that will stay in the planting container for months on end. You can mimic this by using sterilized garden soil or compost as well.

Peat-Based

• In peat-based or soil-less potting mixtures, course sphagnum peat replaces the sterilized soil. Equal parts of the peat and perlite or vermiculite combine to form a very lightweight mixture suitable for seedlings and short-term container plants. Roots grow easily in the sterile mixture, but nutrients are low and the pH tends to stay on the acid side. Be careful to keep these mixtures from drying out as they are hard to rehydrate.

Lime

• Since peat moss tends to increase the acidity of the homemade and store-bought potting mixtures, you add lime to bring the soil up to the pH that most plants require for growth. Add 2 oz. of ground limestone to a half bushel of potting soil to raise the pH enough. Test the acidity of the mixture after you dampen it with a simple pH tester, available at most garden centers.

Fertilizers

• Plants need nutrients, and potting soils only hold so many nutrients. Start adding a liquid fertilizer of 5-10-10 every couple of weeks to plants growing in pots, especially in soil-less mixtures. Stores sell potting mixtures with fertilizer already added, suitable for one growing season. To avoid worrying about fertilizers, add a slow-release granular fertilizer according to the manufacturer's instructions into the mixing container when you make your potting soil.