Pruning is the most common
tree maintenance procedure. Although forest trees
grow quite well with only nature's pruning,
landscape trees require a higher level of care to
maintain their safety and aesthetics. Pruning should
be done with an understanding of how the tree
responds to each cut. Improper pruning can cause
damage that will last for the life of the tree, or
worse, shorten the tree's life.
Because each cut has the potential to change the
growth of the tree, no branch should be removed
without a reason. Common reasons for pruning are to
remove dead branches, to remove crowded or rubbing
limbs, and to eliminate hazards. Trees may also be
pruned to increase light and air penetration to the
inside of the tree’s crown or to the landscape
below. In most cases, mature trees are pruned as a
corrective or preventive measure.
Routine thinning does not
necessarily improve the health of a tree. Trees
produce a dense crown of leaves to manufacture
the sugar used as energy for growth and
development. Removal of foliage through pruning
can reduce growth and stored energy reserves.
Heavy pruning can be a significant health stress
for the tree.
Yet if people and trees are to
coexist in an urban or suburban environment, then we
sometimes have to modify the trees. City
environments do not mimic natural forest conditions.
Safety is a major concern. Also, we want trees to
complement other landscape plantings and lawns.
Proper pruning, with an understanding of tree
biology, can maintain good tree health and structure
while enhancing the aesthetic and economic values of
our landscapes.
Pruning Techniques
Specific types of pruning may be
necessary to maintain a mature tree in a healthy,
safe, and attractive condition.
Cleaning is the removal of
dead, dying, diseased, crowded, weakly attached, and
low-vigor branches from the crown of a tree.
Thinning is the selective
removal of branches to increase light penetration
and air movement through the crown. Thinning opens
the foliage of a tree, reduces weight on heavy
limbs, and helps retain the tree’s natural shape.
Raising removes the lower
branches from a tree in order to provide clearance
for buildings, vehicles, pedestrians, and vistas.
Reduction reduces the size of
a tree, often for clear- ance for utility lines.
Reducing the height or spread of a tree is best
accomplished by pruning back the leaders and branch
terminals to lateral branches that are large enough
to assume the terminal roles (at least one-third the
diameter of the cut stem). Compared to topping,
reduction helps maintain the form and structural
integrity of the tree.
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