• Nitrogen (N) – Nitrogen is largely responsible for rapid growth of green leaves.
• Phosphorus (P) – Phosphorus is largely responsible for root growth, as well as flower and fruit development.
• Potassium (K) – Potassium is a nutrient that helps the overall functions of the plant perform correctly and supports the plant’s vitality. (Note that potassium is usually provided in the form of potash, also known as K2O)

The fertilizer numbers’ percentages are calculated by weight. The remainder of NPK fertilizer ingredients are generally sand or ground limestone, and sometimes micronutrients. Occasionally you will also see another number added to the fertilizer numbers. That final number represents the amount of sulfur in the mix.

A fertilizer that contains only one macro-nutrient will have “0” in the other values. For example, if a fertilizer is 10-0-0, then it only contains nitrogen

These fertilizer numbers, also referred to as NPK values, should appear on any fertilizer you purchase, whether it is an organic fertilizer or a chemical fertilizer.