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  • Writer's pictureKassi K.

Tree Fertilization: Should You Fertilize Trees?

Trees are a part of nearly every landscape, and the benefits of trees are endless! They add monetary value to any property, bring shade to your yard, help shield your home from the elements, bring beauty to any area, create privacy, and attract a plethora of wildlife that helps sustain a biodiverse environment. And while trees of all kinds often seem mostly self-sufficient, they still can benefit from some special care and attention for them to grow strong and stay healthy. While fertilizing your trees is a relatively simple process, if it isn't done right, you can cause devastating damage to your trees. That is why we are here to walk you through some of the dos and don'ts of fertilizing your trees.

Fertilize Trees

Do Trees Need to be Fertilized?

The answer to this question is yes! Especially here in Colorado where our native soil is dense, alkaline, and lacking nutrients, your deciduous trees, evergreen trees, and fruit trees will all greatly benefit from being fertilized. The three primary nutrients in most fertilizers are nitrogen, phosphorous, and potassium. Of these three nutrients, nitrogen encourages the most growth in trees and is also the most limited nutrient in our soils. If your trees are not getting enough nitrogen, they will begin to slow their growth or experience stunted growth altogether. So, if you want your trees to continue to grow, supplementing the soil around your trees with some additional nutrients is highly recommended!

When Is the Best Time to Fertilize Trees?

Timing your fertilizations is just as important as fertilizing itself. If you fertilize at the wrong time of year or during the wrong stage of growth, your efforts could prove to be counterproductive. Here are a few things to keep in mind when planning to fertilize trees.

Fertilize at the Right Time of the Year

The best time to fertilize your trees is either in early spring 4-6 weeks before the buds on your trees begin to emerge or late in the fall season after the leaves have dropped but when soil temperatures are still at or above 40 degrees Fahrenheit. Be sure to avoid fertilizing your trees in the late summer or early fall as this can actually affect the way your tree prepares for winter and can compromise its hardiness.

Fertilize Your Tree During the Appropriate Phase of Growth

It is also very important to be aware of the phase of growth that your tree is in, because fertilizing when it is in the wrong phase of growth can also prove to be counterproductive. Your trees go through three general phases of growth. They go through an Establishment Phase, followed by a Growth Phase, followed by a Mature Maintenance Phase.

During the Establishment Phase, your tree's main objective is growing strong roots and establishing itself. In general, a newly planted tree will be in this phase for 1 year per inch in diameter. For example, if you plant a tree with a trunk that is 3 inches in diameter, it will take approximately 3 years to fully establish. Fertilizing during this phase is not recommended because fertilizing encourages canopy growth and diverts energy away from the roots of the tree to its leaves. And as you can probably imagine, if the roots of your tree aren't able to fully establish, this will not lead to a strong and healthy tree in the long run.

The Growth Phase is the ideal phase for tree fertilization. You will know your tree has transitioned to this phase because you will begin to see significant branch growth. During this phase, fertilization will encourage more rapid growth.

During this phase, it is still good to fertilize, though your tree will not need to be fertilized nearly as much as it was during its growth phase. It is very important to be careful not to overfertilize a tree that is in this mature state, because overfertilizing can force excess canopy growth that the tree and its root system may not be capable of sustaining, potentially leading to an early decline in health.

How Often Should I Fertilize My Trees?

Generally, fertilizing your trees 1-2 times per year in the early spring or late fall is all that is needed. Every tree or shrub is different and may have different growing needs, so you can always consult your local plant nursery for tips or suggestions on how much and how often to fertilize your trees.

What Fertilizer is Best for Trees?


There are tons of different types of fertilizers out there. The types of fertilizers most people are probably most familiar with are granular fertilizers or liquid fertilizers, which those will usually not be very effective for use on your trees. Especially if your trees are planted in a lawn and are surrounded by grass, the grass will use up all the nutrients provided by the fertilizer before the trees roots can get to them. Because of this we recommend using fertilizers that can be applied below the soil's surface. This can be done either by using fertilizer spikes that are driven into the ground and then dissolve over time, allowing the fertilizer to bypass the grass and get deep down to the trees roots. You can also ensure nutrients get to the roots of your tree by using a root feeder. We also recommend using a slow-release tree fertilizer. Trees are large and grow slowly, so using anything other than a slow-release fertilizer could overwhelm or damage your tree. Over-fertilizing can easily cause substantial damage to your tree and is not something that is easily reversed.

How Do You Fertilize a Tree for Planting?

If you are about to plant a tree and are wondering if there is anything you can do to help stimulate its growth right from the get-go, we have two things we recommend: make sure you are planting in healthy soil that is rich in organic materials, and use a root stimulator when planting to help encourage strong root growth.

Plant Your Trees in Healthy Soil

The best thing you can do when preparing to plant your tree is to ensure the soil is healthy. Our Colorado soil is dense and clay-heavy, which means that it holds onto a lot of water and is also difficult for roots to penetrate. Amending your soil with organic materials such as compost and other additives will help loosen up the soil, help it drain better, encourage the presence of beneficial insects, and naturally introduce nutrients into the soil. Mixing granular fertilizers into the soil or immediately watering with a liquid fertilizer is not recommended, as this will just tell the plant to grow leaves instead of focusing on growing strong roots, as was mentioned above. To learn more about best practices when planting trees, check out our Tree & Shrub Planting Guide.

Use MYKE Tree & Shrub Root Stimulator

MYKE Tree & Shrub Root Stimulator

Dispite this product looking similar and being used similar to that of normal granular fertilizers, it is quite different from a tree fertilizer. MYKE Tree and Shrub is an all-natural product that helps to encourage superior growth, extending the life span of trees and shrubs, and accelerating recovery from transplant shock. This product contains mycorrhizae (mai·kuh·rai·zee) which is a fungus that forms a symbiotic relationship with the roots of your plant. When planted together, they benefit each other mutually, and the result of this is a plant that has an increased survival rate, requires less water, flowers and produces fruit more abuntantly, and displays rapid growth and development. This product is organic, easy to use, and is available for purchase at our Garden Center. Learn more about MYKE Tree & Shrub and shop for it online today!

How to Fertilize Trees in Colorado

Knowing how and when to fertilize your trees, as well as what products you should and shouldn't use is so important if you want to maintain strong and healthy trees. Bath Landscape & Irrigation provides premium landscape design and installation services, and we put the utmost care and attention into ensuring your landscape is installed expertly. With the care we put into every landscape, we want to make sure that you as a homeowner are properly equipped to take care of your new yard. That is why we are here to help educate you and ensure you understand how to take care of your landscapes. For more helpful information, check out our blog!


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