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Tree Fertilization
Home  > Tree Care  > Tree Fertilization

Having a tree care service apply tree fertilizer to your landscape trees and shrubs is one of the best tree maintenance services to provide for the care of trees and shrubs. Tree diseases, insect pests, and dead or broken tree branches are obvious signs that a landscape tree or shrub is in need of care. A trees’ requirement for tree fertilizer is a less obvious tree maintenance need, but is a very important tree maintenance practice that will encourage tree health.

Seeing forest trees thrive without fertilization gives the impression that tree fertilization isn’t necessary to maintain tree health. There are, however, two major environmental differences with the growing conditions between forest trees and landscape trees. Forest trees derive nutrients from the natural decay of organic matter, such as tree leaves and trees branches. This natural cycle is interrupted in a maintained landscape when we rake up leaves and remove fallen tree branches. Secondly, in many cases most, if not all, organic matter is removed from urban soils during the home construction process. The lack of naturally derived nutrients, less than ideal urban soils, and harsh environmental conditions puts landscape trees and shrubs under stress and increases the importance of a tree fertilizer program.

Implementing a tree fertilizer program will usually improve the appearance of trees and shrubs and help the trees and shrubs recover from attacks by insect pests. Healthy trees can withstand tree diseases better than stressed trees and will also be less susceptible to decline if subjected to drought. Fertilizing trees after tree trimming is done will also help speed the growth of callus tissue to cover the tree wounds.

The three most common methods used to fertilize trees are soil injection of tree fertilizer, broadcasting tree fertilizer under the tree canopy, or tree trunk injection of tree fertilizer. Each of the tree fertilization methods has benefits and drawbacks. Using any of the methods to fertilize landscape trees is usually better than not fertilizing the trees.

Soil injection of tree fertilizer is often referred to as deep-root fertilization. The delivery system to apply the tree fertilizer consists of a soil probe that distributes the tree fertilizer laterally at a depth of 6 - 10” below ground level. This tree fertilization method often results in the greatest amount of fertilizer being supplied to the tree or shrub. If the arborist from the tree service utilizes a grid pattern to distribute the tree fertilizer then it is likely that the entire root zone under the canopy of tree will be saturated with tree fertilizer. Some arborists may utilize the same equipment to apply tree fertilizer, but will only do one or two rings of fertilization under the canopy of the tree. Both methods of tree fertilization put the tree fertilizer where it is needed, which is below the root zone of grass roots. The cost of the grid fertilization method will usually be higher due to the extra material and labor required, but the results of the tree fertilization will also be greater. A second benefit of a tree fertilizer program using the deep-root fertilization method is that some soil aeration will also take place because the tree fertilizer is applied under high pressure. The only draw back to the deep-root fertilization method is that there may be some excessive turf growth in the areas where the tree fertilizer comes into contact with the grass roots.


Broadcasting tree fertilizer under the tree canopy is a quick and easy method to fertilize a tree. The ease of applying the tree fertilizer is the main benefit of this method of tree fertilization. Usually, the arborist applies less tree fertilizer when using this method of tree fertilization, which means the tree will receive less benefit from the fertilization. If there is grass under the tree then the grass is going to intercept some of the tree fertilizer before is reaches the tree roots.

Trees in need of fertilization are sometimes located in areas where applying tree fertilizer to the tree roots isn’t practical. The root zone of the tree may be covered by a deck or surrounded by a high amount of hardscape. Although any nutrient can be applied with a tree trunk injection of tree fertilizer, this method of tree fertilization is often used by arborists and tree services for special circumstances. The most common use of the tree trunk injection method of tree fertilization is to supply micronutrients to a tree. If the soil pH is too high, or too low, certain nutrients cannot be absorbed by the tree roots. Applying these micronutrients to the soil may, or may not, make them available to the tree. A tree trunk injection is the only way to be sure the tree will receive the necessary micronutrients.

Sometimes arborists are called out when tree decline has reached the point of no return. Having a tree fertilization program in place is simply a natural way to maintain tree health, but is not a cure-all for all tree problems. Protecting trees during construction, tree spraying, and tree trimming are other tree maintenance practices that may need to be done to maintain tree health.

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