Fertilizer for Evergreen Trees

Although evergreen trees can grow tall and stay green all winter, they require the right kind of nutrients to grow. Because of this, several fertilizers have been devised that not only provide nutrients designed for evergreen trees, but also to protect them from infection and from improper soil acidity.

Liquid fertilizer should be used on evergreen trees when they are very young or when they have been the victim of disease or malnutrition. Liquid fertilizer is the most direct transmission of fertilizer available, since it is already in a liquefied state that can be readily absorbed by the tree. This means the tree will get a fast infusion of nutrients such as nitrogen and phosphorus which are necessary for the tree's development. Although this type of fertilizer is easy to absorb all at once, it can damage the tree if administered regularly. Evergreen trees are evolved to receive a steady stream of nutrients throughout their active period, and too much can overload their systems and even lead to root burn.

Feed granular fertilizer to evergreen trees in early April, or just before the active growth period of the plant. This type of fertilizer is solid and releases nutrients slowly as it is eroded by rain or irrigation. The University of Minnesota Horticulture Extension recommends a mixture of 10-8-6 fertilizer, with 10 percent nitrogen, 8 percent phosphorus and 6 percent potassium. Granular fertilizers should be used only on soil that does not have enough of these elements, so a soil test is also recommended. Although many soils are appropriate for evergreen trees, soils that may require granular fertilization include very sandy or heavy clay soils. Granular fertilizers are timed to release over a period of one to three months.

Although many evergreen trees grow in soil that is mildly acidic, soils with a pH of 7.5 or higher can prevent evergreens, such as the white pine, to become chlorotic. This condition prevents the tree from producing enough chlorophyll to enable photosynthesis. Adding a fertilizer that includes lime will reduce the pH of the soil as well as give the plant a fortifying dose of nutrients to help it get back on the track of healthy development.

Although evergreen trees growing in less than ideal soil require fertilizer to maintain healthy development during the growing season, this is not so during the winter, when the tree stops actively growing. Laying fertilizer down that will not be absorbed invites soil-borne bacteria and infection. Do not fertilize evergreen trees during their dormant cycle.