Fertilization to plants is like food to us. Many of us place plants in our landscape, or hire a landscaper, and assuming he adds fertilizer (we use a slow release prill), it’s duration is for that season, winter to winter. This means that the coming spring, especially if it has been a rainy winter(fertilizers leach through the soil profile), the plant is “hungry”. Now some plants seem to grow just fine without anything additional. They have lower fertility requirements, and can “pull” the necessary elements from the soil. However, even these hardier species would benefit from yearly or bi-yearly applications. This service can be done by the homeowner or hired out. On our commercial properties we accomplish this by applying a product that has fertilizer and weed control in the same bag. We apply it twice a year, and in some cases apply a supplemental fertilizer to high end users such as palms, star jasmine(in certain soils), azaleas, camellias etc.
A good choice of fertilizers for plants depends on the plants. Take for example a 15-15-15, typically called an all purpose fertilizer. It is not called that because the numbers are all the same, but because of what the numbers represent. The first number is for nitrogen, which promotes green leaves and growth. Many lawn fertilizers have this as their highest number. The second number is for phosphorus, which encourages root growth and flowering. Therefore, fertilizers for Azaleas, Camellias, and Roses will have this second number as their highest number. Since “fruit” comes from flowers, your vegetable and fruit tree fertilizers will also have this as a higher number. The difference in the Azalea/Camellia fertilizer is that it will have a more acid PH, being that these plants do better in a neutral to slightly acidic soil. Lastly, potassium is credited for developing healthy tissue, cell wall and rigidity in the plant. It also has properties to help protect against pests and diseases. In combination these Macro elements do a lot to keep the plant growing, and hence their importance. Now that you understand how the nutrients work, you can “play” with the ratios, depending upon what your plant material is.