Tree Fertilization

If we are lucky, our properties have soil structures filled with nutrients our native plants thrive on. Those structures can also be full of clay, causing problems for non-native plants and landscapes in the Denver area. Soil imbalances, compaction and use of chemicals and inappropriate organic products sometimes make tree fertilization a necessity.

Taking a page from nature’s handbook, we at Arbortec Tree Service recommend solutions to your tree care that mimics what’s missing in the environment as a first course of action. When necessary, we supplement this with injectable applications of fertilizer to target specific needs. Let’s talk about nature’s way, first.

Plant health care specialist with a soil probe administering fertilizer to a nearby tree's roots in Denver CO

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Nature’s Fertilizer


Soil structure supports the nutrients trees and shrubs require to live. It builds up from a combination of mineral breakdown and additions of organic matter, and it takes thousands of years to develop.

As the Master Gardeners at Colorado State University Extension note, human landscape stewards can move the process along faster by adjusting the soil’s composition in good ways. Here are some examples of natural solutions.

Leave the mulch behind: Tree leaves have been deemed unsightly and could spoil a lawn. However, they are also some of the best natural fertilizer for your landscape. Use a mulching mower to break them into small pieces and let decomposition do the rest.

Ditto on grass clippings: Tree roots extend past the dripline, the canopy overhead. Mulching those grass clippings and leaving them behind to break down over time is another great form of natural fertilizer.

Add organic matter: This is the blanket recommendation for all fertilization. Decomposed plant material and clean manure are two examples you can use, if the additions come from sources certified to be pest and chemical free.

Limit your lawn: Lawns that extend up to a tree trunk often use what nutrients might be available, making it harder for the tree to gather what it needs. Leaving a large area mulched with clean (uninfected) woodchips out to the dripline offers both protection for the roots and trunk and nutrients as they decompose.

Plan your plants: While a shade garden under a tree canopy can be beautiful, it also uses nutrients the tree needs and upsets watering balances. Consider putting pots of plants under the tree instead of planting in the ground.

Consider water needs: Once established, most landscape trees do not need watering. In addition to encouraging roots to grow near the surface or drowning them, overwatering leaches valuable nutrients from the soil.

The next time you take a walk in a wild woodland, examine the world at your feet. Then take that approach back to your urban forest. Fertilizer does grow on trees!

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When Fertilization Helps


In some cases, it is clear the tree or shrub lacks something specific in terms of nutrients to survive. Indications range from abnormal leaf colors to dieback. These symptoms can have more than a single cause. That’s why it is necessary to have a Certified Arborist at our Denver tree service diagnose the problem.

Fertilizer can help a tree recover from excavation in the root zone, weaknesses due to pests or diseases, and storm damage. Sometimes, it’s matter of a good tree planted in the wrong place. Our professionals at Arbortec assess the condition of the plant and determine probable causes for its weaknesses.

We take samples of your soil and send those to a lab to determine the soil structure and available nutrients. We inspect the tree for possible issues and damage. We ask you questions about what might have been occurring near the structure, like applications of insecticides, herbicides, or chemicals for other issues.

We find out why your tree is suffering before suggesting any treatment. Solutions could take the form of injections into the tree itself, injections into the soil, one-time treatment, or multiple dose frequency over time. Issues such as the season, where the tree is in its growth or lifecycle, and surrounding conditions also impact our care.

Call our Certified Arborists at Arbortec Tree Service in Denver to determine what, if any, fertilization will help your trees. We promise to treat your trees as if they are our own.

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