Flower food is a type of fertilizer used on flowering plants to increase the number and size of blooms. Most flower foods contain the three main macronutrients--nitrogen (N), phosphate (P) and potassium (K). Some may contain one or more micronutrients. The percentage of each macronutrient is listed on the front of the fertilizer container. For example, 10-10-10 means there is 10 percent each of nitrogen, phosphate and potassium. Micronutrients are usually listed on the back of the container.
The first number listed on a fertilizer label is nitrogen. It is important in the production of chlorophyll, which causes the green color of plants. It is also used for leaf and stem growth. Plants use more nitrogen than any other nutrient. A key symptom of nitrogen deficiency is yellowing foliage.
Phosphate is the second number listed on a fertilizer label. It is vital to seed germination, root growth and fruit growth. Wilted purplish foliage may indicate a deficiency of phosphate. It does not leach out of the soil and may inhibit the use of some micronutrients.
Potassium, also known as potash, is listed third on a fertilizer label. It is important in the production of sugars, starches and proteins. It helps plants to withstand stress from drought, pollution, disease and other factors. Signs of potassium deficiency include poor drought tolerance, reduced growth and increased occurrence of diseases.
Some flower foods contain one or more micronutrients, especially those formulated for particular species of plants, such as azaleas, roses or annuals. Iron (FE), magnesium (Mg) and manganese (Mn) are used in the production of chlorophyll. Sulfur (S) helps a plant with photosynthesis and boron (B) assists in the transportation of sugar. Copper (Cu) and zinc (Zn) are used in the production of proteins, while plants use calcium (Ca) to develop strong root systems.
Have the soil tested by the local county extension office or other soil-testing laboratory before any flower food is applied. Apply only the nutrients that are not available in the required amounts in the soil. The flower food should be worked into the soil thoroughly with a hoe or rake before planting, or watered in well before or after planting.