Whether you're starting seed, repotting house plants, or assembling big pots of flowers for summer, it helps to use potting soil that already contains nutrients. You can buy ready-made, fortified mixes (nutrient contents are listed on the label) or make your own with the following controlled-release organic recipe.
Start by pouring a gallon of potting mix onto a potting bench. Add 1 tablespoon each of blood meal for nitrogen, kelp for trace elements, and greensand for potassium; then add 2 tablespoons of bone meal for phosphorus. Mix it all together and you're ready to plant.