All plants need a basic amount of macronutrients and micronutrients for good health. The three main macronutrients that are found in fertilizers are nitrogen, phosphorus and potassium. These make up the NPK in the value ratio found on plant food packages. In addition to these three nutrients, plants need micronutrients and trace minerals. Most plant food formulas include a percentage of these as well. Blooming plants have specialized nutrient needs. Phosphorus is a promoter of bloom formation and fruiting on plants.
What Phosphorus Does
Phosphorus content is represented by the middle number in fertilizer labels. Phosphorus is a part of the photosynthesis process that produces food for the plant by converting sunlight to plant sugars. In addition to sugars, phosphorus helps create starches and oils. Blooming requires a lot of energy and phosphorus helps the plant supply that energy. Phosphorus helps form a strong root system and sturdy plant structure and is often high on the list of ingredients in starter fertilizers and bloom busters.
Types of Phosphorus
Bloom busters are high in phosphorus and are also referred to as super phosphorus foods. They can increase flower yield and are used by exhibition and champion growers for bigger, brighter flowers. You can add phosphorus to the soil in organic compounds and natural formulations. Bone meal and rock phosphate are commonly used with roses and other blooming shrubs. Soils contain some naturally occurring phosphorus but the phosphorus is often leached out of soil by heavy watering and rains.
Phosphorus Cautions
Some companies market fertilizers with excessive amounts of phosphorus with the promise of astounding flower production. Alabama Cooperative Extension and its master gardeners performed an experiment to see if the application of excess phosphorus really encouraged more and bigger blooms. The research determined that there was no discernible difference in the number of blooms that the overly fed and control groups attained. The only difference was the buildup of phosphorus in the soil; it accumulated at unhealthy levels. High levels of phosphorus in soil can increase salinity, which many plants cannot tolerate.
Application of Phosphorus
Phosphorus can be applied in a liquid or granular form. Some products are simply spread around the base of the plant on the soil. Others require that it be worked in or mixed with water and dispersed. A soil test should be performed before planting any new flowering tree or bush. It is easiest to add phosphorus before the plant is in the soil. Phosphorus moves very slowly through soil and initial incorporation ensures that the plant will have ready access to the nutrient.
