Before doing
routine fertilization, ask yourself if you want this plant to
grow. When a plant is young and small and you want it to grow
rapidly, yearly fertilization is necessary. As a plant gets
larger, proper fertilizer applications can be used to control
the growth and reduce the need for excessive pruning.
Generally, the more fertilizer you use, the more the plant
will grow. Once a plant has reached its desired size, reducing
or eliminating fertilizer will limit its growth.
If you determine that your shade trees need fertilization,
this can be done in fall when the leaves start to change color
and drop. Draw an imaginary circle about twice the diameter of
the trunk around the base of the tree. Imagine another circle
just beyond the spread of the outer most branches. These two
circles will be the starting and the finishing point when you
fertilize. From the starting circle near the trunk, make a
series of circles 2 feet apart to the outer circle. In each
circle make holes with a crowbar or probe about 2 feet apart
and 12 to 15 inches deep. You want the holes deep enough to
get the fertilizer down into the root zone. Evenly distribute
the fertilizer in the holes. Cap the holes with peat moss,
sand or soil. Water the area generously.
A soil test is the best way to determine the nutrient needs
of your tree. But without a soil test, a general rule of thumb
for shade trees is 1 – 2 pounds (1 – 2 pints) of high
nitrogen, complete fertilizer per inch of trunk diameter. A
tree with a trunk diameter of 5 inches will need 5 – 10
pounds (5 – 10 pints) of fertilizer. A complete fertilizer
will have 3 numbers on the front of the bag. The first number
lists the amount of nitrogen in the product. Fertilizers with
the numbers 12-6-4, 16-8-8, and 20-10-5 are generally best for
fall fertilization.
You can use a different fertilization method with young
trees. Just apply a double rate of slow release lawn
fertilizer over the root area when you fertilize your lawn in
fall. And again, water in.
Evergreens can be fertilized in late fall with either
well-rotted manure or the same high nitrogen fertilizer that
you used for shade trees. If using the manure, apply as a
surface mulch or dig the manure into the soil around the
plant. The commercial fertilizer is applied at a rate of 1/3
pound (1/3 pint) per foot of height or spread on the
evergreen, whichever is greater. A 6-foot tree needs 2 pounds
(2 pints) and a tree with a 5-foot spread would need 1 2/3
pounds (1 2/3 pints). Dig the fertilizer into the soil around
the plant using care not to let it touch any part of the
plant. Water the fertilizer in well.
Apply fertilizer to deciduous shrubs in late fall also. Use
the same high nitrogen fertilizer that you used for shade
trees and evergreens. Apply at a rate of 4 oz. per foot of the
shrub’s height or spread. If the shrubs are planted in beds
of bare soil, apply 2 pounds (2 pints) per 100 square feet of
bed area. Shrubs that are mulched with organic mulches like
bark and wood chips require regular applications of nitrogen
because the organic matter removes nitrogen from the soil as
it decomposes. Spring is a good time to remember to apply this
additional nitrogen.
