Trees in the landscape add shade, create lighting effects and provide privacy from the prying eyes of neighbors. They are also a costly addition. Regular application of fertilizer is required to keep your tree healthy throughout the year and protect it from cold winters, when nutrients are not in abundance.
Like all plants, trees require nutrients to survive. As a tree grows, it absorbs nutrients from the soil. If the nutrients are not replaced at a greater rate than they are diminished, the soil becomes infertile and the tree suffers. Trees mainly need an application of the macronutrients nitrogen (N), phosphorous (P) and potassium (K), says the University of Minnesota.
Organic vs. Inorganic Fertilizer
Use organic or inorganic fertilizers to supply nutrients to your plant. Inorganic fertilizers are available in quick- or slow-release forms. With slow-release varieties, a coating over the fertilizer slowly releases nutrients over a period of time, while quick-release fertilizer breaks down easily. Organic fertilizer breaks down slowly but also adds organic matter to the soil, improving its quality.
Perform a pH test on the soil in which the tree is planted, recommends Clemson Cooperative Extension. Use a store-bought pH testing kit, or send soil samples off to your local university extension. A pH test will indicate what the soil acidity is, and some will tell you the level of nutrients in the soil. Nutrients are added to make up for soil deficiencies.
Apply fertilizer according to nitrogen weight. Trees usually require 2 to 4 lbs. of nitrogen per 1,000 feet of root spread per year. Late fall, after leaves from the tree have fallen, is the best time to apply fertilizer, says the University of Tennessee. Further applications are made in the winter and in the spring before active growth begins. Apply to the entire root area and water the fertilizer gently after application.
Tree fertilizers come in many forms, including dry granules, spikes, liquid and injections. Dry granules are spread using a broadcaster and are then watered to break the fertilizer down. Spikes are pushed into the soil, where they slowly disintegrate. Liquid fertilizers are sprayed onto the root zone area. Microinjections are used to invigorate dying or sick trees. An injection of nutrients is made directly into the tree trunk.