Fertilizing Landscape Trees and Shrubs part 1

Maintenance plans should be produced for trees and shrubs in your landscape. An effective care program includes monitoring and keeping insect and disease problems in line along with restraining weed competition, and giving well timed applications of water, mulch, and fertilizer.

Tree and shrub fertilization is especially important in urban and suburban areas of the country where soils have been altered due to construction. These urban soils tend to be heavily compacted, poorly aerated, poorly drained, and low in organic matter. Even where soils have not been affected, fertilization may be needed as part of a maintenance program to increase plant vigor or to improve root or top growth.

Trees and shrubs in residential and commercial landscape plantings are frequently fertilized to keep them healthy and attractive. Over-fertilization is prevalent, causing excessive growth, especially on young nursery stock. Trees growing in lawn areas usually receive some nutrients when the grass is fertilized. This is usually sufficient to maintain most trees in fertile soil. However, fertilization may be desirable on altered soils where unconsolidated fill material has been added or the topsoil has been removed. Managed urban areas where fallen leaves are taken off may also require a fertilization regime to enrich soil and replenish nutrients.

Fertilizer is no stand-in for environmental factors, such as sunlight and water, which must be in balance if a tree or shrub is to grow into its full potential. Trees and shrubs that are healthy and growing robustly are less susceptible to attack by insects and diseases. An application of fertilizer may, in some instances, improve the plant's resistance to further infestations of certain pests. For example, maple trees will recover from mild cases of Verticillium wilt following applications of nitrogen fertilizer.

Fertilizer Objectives
How and when to fertilize landscape trees and shrubs depend on:
Maintenance objectives (stimulate new vs. maintain existing growth)
Tree and shrub ages (generally more for younger and less for older plants)
Plant stress levels

When to Fertilize
The top time to fertilize trees extends from late fall, after the leaves have fallen, through the winter and into early spring before vigorous new growth occurs. Fertilizer applied in the fall has a longer time period to penetrate the soil enabling the roots to more efficiently absorb it. The fertilizer is taken up by the roots during the winter and is available to the plant for growth in the spring.

Trees that are fast growing should be fertilized yearly. Well-established, mature trees usually require fertilizer once every three to four years.

Fertilizing Newly Planted Trees
Freshly planted trees typically do not need fertilizer during the 1st growing season. Almost all transplanted trees produced in the nursery have elevated levels of nutrients that last through the 1st growing season. Exuberant fertilization during the first year could harm the tree and cut back its rate of development. After the 1st year, nitrogen can be utilized in a roughly 3ft area around each tree. This will assure a satisfactory supply for continued development. Don't apply fertilizer within 12 inches of the stem of the tree since fertilizer can burn and injure young stem tissue.