Tree and Shrub Fertilizing

I often hear "nobody fertilizes the forests trees"... why should I fertilize my trees? 

Trees growing in a forest live in a balanced... natural environment. The nutrients that are absorbed from the soil eventually fall to the ground in the form of leaves, needles, fruit, and branches. This organic matter accumulates on the ground where soil microorganisms decompose it, returning the nutrients back to the earth. Fine absorbing hair roots grow up into the decaying organic matter... reabsorbing the nutrients and starting the cycle over again.

Let's take a look... at where we plant trees!

In the urban forest each autumn we gather up the nutrient containing leaves... and give them to the trash man. We plant turf grass over the trees root systems, or worse... we cover the roots with plastic or landscape fabric, and cover that with decorative rocks. We stuff trees into tiny planting pits in sidewalks and parking islands without any consideration for future growth... then we expect them to grow and thrive!

When we remove natures natural fertilizing process...
we must supplementally feed our trees! 

Some common methods to fertilize trees and shrubs include:

• Liquid fertilizer soil injection... This is done by dissolving fertilizer into water and then injecting it into the soil around the root zone of the tree. A common tool for the homeowner to use is the Ross Root Feeder... which works fairly well. For a more thorough application it's better to hire a professional tree company who has specially equipped trucks that are able to inject the fertilizer solution under much higher pressure.
• Topical applications... Granular or diluted liquid fertilizer is spread across the soils surface. When the fertilizer gets wet... nutrients are washed down to the root zone.
• Trunk injection... This method bypasses the root system and puts nutrients directly under the bark of the tree where they are dispersed through the sap system. Trunk injection is usually done to correct specific nutrient deficiencies like iron chlorosis. This treatment should only be performed by a trained tree expert!

All plants need 16 essential elements to function. Nitrogen, phosphorous and potassium (NPK) are generally the 3 limiting elements... and are the main ingredients in fertilizer formulations. It really doesn't matter what the package says... Rose food, Flower food, Tree food, etc. As long as it contains NPK... plants will use it. In Colorado the most common micronutrient deficiency is Iron. Chelated formulations work the best in our soils.

There is much more to fertilizing than we have space for here. If you are in doubt about how, when, where and why to fertilize trees and shrubs, consult with a professional!

Article written by: Kevin Jones, President - Jones Tree & Lawn, Inc.

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