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Pruning
Trees
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Early spring is a great time to prune trees—except
in the middle of an early spring blizzard, of
course. The subject of pruning trees is one which
generates much confusion for do-it-yourself tree
trimming homeowners. First, it needs to be said
that pruning large trees is dangerous work that is
best left to trained arborists. Paying an arborist
several hundred dollars to prune a medium to large
shade tree is downright cheap compared to the
hospital or mortuary expenses associated with
falling out of a tree with a sharp saw in your
hand. However, pruning small trees is a task that
can be successfully performed by most homeowners
with only a small amount of training and a large
amount of caution.
Most
young trees need a small amount of formative or
corrective pruning every two to three years. This
early pruning helps trees develop a good branching
structure for what will become its largest lower
limbs as the tree matures. By insuring that these
limbs are well spaced and limbs which are strongly
attached to the truck, you can greatly reduce the
chance that your tree will be injured by high winds,
heavy wet snows, the neighbor’s tree-climbing kids,
and all of the other common causes of serious
injury to trees.
A common pruning mistake is to simply prune off all
of the lower branches as the tree grows. It is
widely, and mistakenly, thought that pruning off
lower branches somehow “forces” the tree to grow
upward. |
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Excessive
and early pruning of lower branches is actually a
harmful practice which slows the rate of growth of a
young tree. Branches hold leaves, and leaves are
the major food making part of trees. By pruning off
young branches too soon, one actually reduces the
health and rate of growth of a young tree.
Often these lower branches are pruned off to make it
easier to mow directly under the branches. Young
trees will grow more quickly if these lower branches
are allowed to remain on the tree until they reach
the size listed above before being removed. To make
mowing easier, simply increase the size of the mulch
circle around the tree. The combination of a larger
mulch circle and leaving lower branches remain on
the tree will produce a much faster growing tree.
The main reason to prune small trees is to insure
that they develop a good strong branching structure
as they mature. This is particularly important for
shade trees, but is also important for smaller
flowering trees and evergreens. The first rule of
pruning is: Look first, cut second. There are
four types of branches that are candidates for
pruning. The task of deciding which branches to
prune is made much easier if you look for and prune
off each type of pruning candidate in turn.
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1. Small “suckering” type branches.
These are small branches that often begin growing on
the lower portion of the trunk. Prune them off
anytime.
2 Broken or severely injured branches
prune them anytime you see them.
3. Branches that are improperly attached to the
trunk.
As a general rule they should be pruned off before
they reach one inch in diameter. The place to
check for poor branch attachment is at the top part
of the crotch where the branch attaches to the
trunk. The bark at this location should form a
small ridge where the branch bark meets the trunk
bark. There should not be a clear or distinct line
at the top of the crotch. A clear or distinct line
at the top of the crotch usually indicates a
phenomenon that arborists call “included bark” where
the annual layers of new bark are growing into the
crotch rather than overlapping each other as they
should. This forms a weak attachment as the branch
gets larger and is one of the major causes of branch
breakage in ice storms and heavy wet snowstorms.
4. Excessive branches.
Shade trees in particular will often form more
branches on the lower trunk than will be able to
develop into large branches—just because they are
too close to the next branch just above or below.
Prune these branches off whenever they reach 1-2
inches in diameter. Always select properly
attached branches to remain.
There is no law that says that the lower
branches of all trees must be pruned off in order to
give a tree its “proper” form. It is true that
trees growing in forests drop their lower branches
as they grow, but this occurs because the dense
stands of trees growing in a forest do not allow
light to reach the leaves of lower branches. When
the leaves on the lower branches can no longer get
enough light to make food, the tree “cuts the branch
off” on its own, and eventually the branch dies and
falls off the tree. However, trees growing out in
the open in natural settings will often develop
large branches quite close to the ground. With
sunlight able to reach the leaves of lower branches
in this type of setting, these lower branches will
continue to push their leaves out into the sunlight,
developing long lower branches and an unusual and
picturesque tree. One way to get rid of some lawn
space is to allow a well-placed tree to grow in this
fashion. The pictures of the large live oaks
growing on southern plantations offer an example of
how some trees can grow if given the opportunity.
Trees that are capable of growing in this way are
bur oak, green ash, honey locust, and Kentucky
coffee tree. |