Fertilizers usually come in 3 numbers which represent the three elements- nitrogen, potassium and phosphorus. Each of the elements has key functions needed by flowers and/or any other plants to ensure optimal results. Nitrogen promotes the growth of plants and is responsible for the plants deep green color of its leaves while potassium is necessary for plants to become disease-resistance, vigor, and provide beautiful colors when in bloom. Phosphorus, on the other hand promotes the growth of roots and flower production. When these 3 elements are present in a fertilizer it's called complete fertilizer.