Plants gather the nutrients needed for healthy growth from the soil. The nutrients are depleted as the plant grows. Plant fertilizer was created to replenish the different nutrients used by the plants. Different fertilizers supply a variety of nutrients so you can put the nutrients needed for specific plants back into the soil and not worry about adding too much of another nutrient.
Fertilizer adds nutrients to the soil so plants, trees and shrubs become established where they are planted, produce lush foliage and grow in a healthy manner. The common fertilizers available in most garden centers contain three macro-nutrients necessary for healthy plants. The three numbers on the bag of fertilizer reflects these nutrients according to content. The first number represents the amount of nitrogen, the next phosphorus and the third potassium. Each ingredient has varying effects on plant life.
Nitrogen in the fertilizer stimulates growth in the plants, causing lush foliage. Too much nitrogen can cause the plants to use any food stored and also decrease the amount of root growth, making the plant weak and top-heavy. The proper amount of phosphorus in the soil promotes new root growth and flower formation. Phosphorus also aids the plant in storing food energy during the growing season. A lack of phosphorus can result in slow root development, low fruit production and spindly growth. Potassium also helps root development and aids in photosynthesis. Plants use potassium to regulate water flow inside the plant. Low potassium levels cause plants to be less drought-tolerant. Potassium also aids the plants in preparing for the winter months. To keep these macro-nutrients working for the plant, it is important to apply the proper amount of fertilizer at the right time.
Fertilizer should only be applied after soil test results determine the need for nutrients in the soil or if you are planting new plants or trees in the landscape. If the test results show a low level of nutrients, add fertilizer in the spring before new growth starts. Do not fertilize plants in late summer or fall because new growth late in the season may be damaged in the winter. Damaged sections of plants and trees are more susceptible to pests and disease. Different types of fertilizer make it possible to fertilize according to the plants needs.
Slow-release fertilizers take longer to dissipate into the soil, allowing the plant to gather the nutrients as needed throughout the growing season. Water soluble fertilizers are applied more frequently than granular fertilizers due to rain waters washing the nutrients out of the soil. Plant-specific fertilizers contain a well-balanced group of nutrients for specific types of plants such as roses, fruit trees or rhododendrons. Avoid over-fertilizing the plants when applying the fertilizer.
Each type of fertilizer contains application instructions on the package. Follow the instructions for each type of fertilizer you choose. Plants can only use the nutrients that are dissolved in the soil. When you apply a granular or powdered fertilizer, water the area after application. Do not fertilize plants before any expected rainfall. The rain washes the nutrients out of the soil and into streams, ponds and other water sources.