Ornamental trees and shrubs planted in fertile,
well-drained soil should not require annual fertilization. Trees
and shrubs that are growing well don't require extra nutrients. If
you have ornamentals that are not doing well, fertilization may be
helpful but only after the problem causing poor growth has been
corrected. Poorly growing plants will exhibit any or all of these
- light green or yellow leaves
- leaves with dead spots
- leaves smaller than normal
- fewer leaves and/or flowers than normal
- short annual twig growth
- dying back of branches at the tips
- wilting of foliage
These symptoms of poor growth may be caused by
inadequate soil aeration, moisture, or nutrients; by adverse
climatic conditions; by wrong pH; or by disease. You should
attempt to determine the specific cause in each particular
situation and apply corrective measures. Do not assume that an
application of fertilizer will quickly remedy any problem
encountered. Do not fertilize trees unless they need it!
The cause of poor growth may or may not be evident.
Ornamentals transplanted or disturbed by construction within the
previous five or ten years may be in shock, their root systems
having been disturbed. Injury from insects, diseases, or air
pollution can stress a tree or shrub. Fertilization of such plants
should be carried out with caution since overstimulated plants may
become weakened, predisposed to diseases, and attractive to insect
pests. Attempts to reduce the adverse factors may be helpful in
restoring plant quality. Correct fertilizer application can also
help. It is important to realize that a complete growing season
may be needed before much response is seen from the fertilizer.
Review the chapter on Soils and Fertilizer to determine
what type of fertilizer and how much to apply. Measure the
distance between the trunk and the drip line and multiply by 125%.
This will determine the radius for the outer boundary for
fertilizer application. Distribute the fertilizer evenly in the
outer 2/3 of the circle defined by the trunk and the boundary.
For example, if the trunk is eight feet from the drip
line, then the outer boundary will be ten feet (8 X 1.25 = 10).
Apply fertilizer around the tree in a doughnut shaped band that is
between 3.3' and 10' from trunk (10 / 3 = 3.3).
A moderate rate of growth and good green color is all
that is desired of woody plants. Excessive vigor, which is evident
by lush green leaves and long shoot growth, is undesirable. Such
plants are more susceptible to injury by cold in winter, are more
likely to be broken during wind and snow storms, and usually will
have a shorter life than those making moderate growth.