Traditionally, trees have been "deep fed" by punching or drilling holes in the root zone and pouring in a 1/2 cup or so of granular fertilizer.  Some tree services even have probes they use to inject liquid fertilizer into the root zone.


Professionals also use injection systems where holes are drilled in the trunk, and anything from fertilizers to pesticides are introduced using capsules (this is very similar to an "I.V." that drips into a person's arm at the hospital).  Also, university research has indicated that surface applications of fertilizer at the right time of year can be just as effective as deep feeding trees. These surface applications are usually timed for late fall or early spring.

Pink tree blossoms
Breathtaking pink blossoms on a Crabapple tree!

It is important to remember that tree roots remain active until the soil drops below 40-degrees Fahrenheit -- this is several weeks after the leaves have fallen in the fall, and a few weeks before they appear in the spring.  These are considered "dormant feedings".  Most trees prefer a fertilizer with a 2-1-1 ratio, such as 10-5-5.


Where to place tree fertilizer

Fertilizers must be placed where the tree can get them, and it's important not to place them too deep --- remember that most tree roots are within 12" to 18" of the soil surface.  Tree size and fertilizer analysis will dictate the actual amount of fertilizer you apply.  To help prevent groundwater contamination, don't apply quick release fertilizers when roots aren't active and nutrients will "leach" out of the rootzone (winter).

Fertilize a tree at planting time?

It's best not to put chemical fertilizers in the hole when a tree is first planted, since this can cause root burn. However, we would recommend using an organic fertilizer (slow release with very little "burn potential") in the soil backfill when planting, with some added phosphorus.

Immobile nutrients

It is very difficult for phosphorus to move downward through the soil profile, so this is your best chance to introduce phosphorus (the middle number on the fertilizer bag) into the rootzone. Bonemeal is the organic source of phosphorus. Super-phosphate (0-20-0)  is the chemical source.  Phosphorus is known to promote good rooting and blooming for those flowering trees.

dogwood in bloom
Wow!  Awesome flowering dogwood in Spring glory


Introduction to Trees

Tree Fertilization

Fertilizer 101


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