Deep Root Injection Fertilization of Trees

A deep root injection is a tree fertilizer that is applied under the surface and near the roots through augured holes. While a tree can be fertilized with a surface application, a deep root injection of fertilizer will put phosphorus and potassium into the root zone while providing the additional benefit of root aeration.
Holes are typically formed by a manual or electric auger around 8-12” deep. They are generally placed around the tree roots with spacing and frequency based on tree size. Holes can be placed on a tree’s drip line (around the edge of the canopy), or near the trunk.
Once the holes are formed, a fertilizer is then applied to the hole and should be watered. A tree fertilizer is typically a blend of 2-1-1 of nitrogen-phosphorus-potassium. The benefit of this root fertilization is a healthier and stronger landscape the following season.