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When Do You Fertilize?

The time to fertilize trees is in the late winter before the buds begin to break open. Avoid fertilizing during periods of drought or excessive moisture. Applying fertilizer to dry soil will burn the roots or break down before it can be watered in by natural rains. During wet periods the fertilizer will be washed away before it can be utilized by the tree. Fertilizers should be applied when the soil is moist. This optimizes the chances that the nutrients you are supplying will get to the tree.

Where Do You Fertilize?

Trees have roots spreading far from the trunk of the tree. These roots reach in all directions from the trunk. The roots which do the actual work of taking up the water and nutrients are the tiny “feeder” roots. These are hair-like roots located in the top layer of the soil. Most of these tiny roots are concentrated under the canopy of the tree. This is where fertilizer should be applied.

How Do You Fertilize?

Fertilizers may be applied in two forms, wet or dry. Liquid fertilizer is usually injected into the soil. Dry fertilizer comes in powdered and granular forms.

Granular fertilizers are easy to obtain and to apply. Broadcasting granules on the soil surface works but does not deliver the material directly to tree roots. If there is grass under the trees instead of mulch, the grass will get much of the benefits. To deliver more of the fertilizer to the tree roots, the fertilizer must be placed under the surface of the soil. Apply the fertilizer into small holes placed two to three feet apart in a grid pattern under the canopy of the tree. The holes should be dup with a pipe, tire tool, steel prybar or bulb planter. The holes should be 8-12 inches deep and one to two inches in diameter. Mix the fertilizer with peat moss or other bulky organic matter. This will help reduce burn and add airspace to the soil. Liquid fertilizer should be injected in the same grid pattern.

How Much Do You Fertilizer?

Very light applications are ideal. With a light approach, more fertilizer can always be added later. Heavy applications of fertilizer can severely damage or kill trees, especially stressed trees.