Fertilizing Shade Trees

Fertilize shade trees after the first year.

Don't fertilize trees during the first year after planting or the top growth may become more than the roots can feed which could cause the tree to die. Fertilizer may also benefit established trees that appear less than healthy.

Shade trees exist in nature without much care, but transplanting them to man-made conditions can cause them some problems. It's especially helpful to fertilize shade trees during the second growing season and thereafter. Don't fertilize trees during the first year after planting or the top growth may become more than the roots can feed which could cause the tree to die. Fertilizer may also benefit established trees that appear less than healthy.

A good fertilizer recipe…

Fertilizer for trees should have nitrogen, phosphorous and potash. Examples of some fertilizers to look for are 8-8-8, 13-13-13 and 12-4-4. Common garden fertilizers such as 8-8 8 are satisfactory. Be careful of weed and feed type fertilizers since they contain herbicides which could harm trees or these fertilizers could even kill trees if they're used long enough.

Too late in the summer…

Fertilize established trees only as needed. Early spring is the best time. If additional nutrients are needed, make a second application in early summer. Don't fertilize trees in late summer because it may cause them to continue to actively grow into the winter months and be damaged by cold weather.

Measuring your tree…

Use one-to-two pounds of fertilizer for each inch of tree diameter. Trees less than six inches in diameter need about two pounds of fertilizer each year. To determine the diameter, measure the distance through the tree, not the distance around the tree, and measure at chest level.

Surface application…

Surface application is one of the easiest ways to apply fertilizer. It can be used on established trees where the soil beneath the tree is free of vegetation such as grass or ground cover. Apply fertilizer evenly under the tree branches. Don't put fertilizer within one foot of the trunk; it can injure the root collar.

Or, punch holes…

If the soil is compacted, or if grass is growing under trees, punch holes six-to-eight inches deep in the soil and put the fertilizer in the holes. Don't put more than a handful of fertilizer in each hole.

For more information on fertilizing shade trees, contact your local County Extension Office.