Proper pruning is essential in developing a tree with a strong structure
and desirable form. Trees that receive the appropriate pruning measures
while they are young will require little corrective pruning when they
mature.
Keep these few simple principles in mind before pruning a tree:
- Each cut has the potential to change the growth of the tree. Always have a
purpose in mind before making a cut. - Proper technique is essential. Poor pruning can cause damage that lasts
for the life of the tree. Learn where and how to make the cuts before picking
up the pruning shears. - Trees do not heal the way people do. When a tree is wounded, it must grow
over and compartmentalize the wound. As a result, the wound is contained
within the tree forever. - Small cuts do less damage to the tree than large cuts. For that reason,
proper pruning (training) of young trees is critical. Waiting to prune a tree
until it is mature can create the need for large cuts that the tree cannot
easily close.
Making The Cut
Pruning Tools
Pin oaks and sweetgums, for example, have a conical shape with a central leader.
Elms and live oaks are often wide-spreading without a central leader. Other trees,
such as lindens and Bradford pears, are densely branched. Good pruning
techniques remove structurally weak branches while maintaining the natural form
of the tree.
Trunk Development
It is important to leave some of these lateral branches in place, even though they
may be pruned out later. These branches, known as temporary branches, also
help protect the trunk from sun and mechanical injury. Temporary branches
should be kept short enough not to be an obstruction or compete with selected
permanent branches.
Permanent Branch Selection
Nursery trees often have low branches that may make the tree appear well-
proportioned when young, but low branches are seldom appropriate for large-
growing trees in an urban environment. How a young tree is trained depends on
its primary function in the landscape. For example, street trees must be pruned so
that they allow at least 16 feet of clearance for traffic. Most landscape trees
require only about 8 feet of clearance.
The height of the lowest permanent branch is determined by the tree’s intended
function and location in the landscape. Trees that are used to screen an unsightly
view or provide a wind break may be allowed to branch low to the ground. Most
large-growing trees in the landscape must eventually be pruned to allow head
clearance.
The spacing of branches, both vertically and radially, in the tree is very important.
Branches selected as permanent scaffold branches must be well-spaced along
the trunk. Maintain radial balance with branches growing outward in each direction.
A good rule of thumb for the vertical spacing of permanent branches is to maintain
a distance equal to 3 percent of the tree’s eventual height. Thus, a tree that will
be 50 feet tall should have permanent scaffold branches spaced about 18 inches
apart along the trunk. Avoid allowing two scaffold branches to arise one above the
other on the same side of the tree.
Some trees have a tendency to develop branches with narrow angles of
attachment and tight crotches. As the tree grows, bark can become enclosed
deep within the crotch between the branch and the trunk. Such growth is called
included bark. Included bark weakens the attachment of the branch to the trunk
and can lead to branch failure when the tree matures. You should prune branches
with weak attachments while they are young.
Avoid overthinning the interior of the tree. The leaves of each branch must
manufacture enough food to keep that branch alive and growing. In addition, each
branch must contribute food to grow and feed the trunk and roots. Removal of too
many leaves can “starve” the tree, reduce growth, and make the tree unhealthy. A
good rule of thumb is to maintain at least half the foliage on branches arising in
the lower two-thirds of the tree.
Newly Planted Trees
Pruning of newly planted trees should be limited to corrective pruning. Remove
torn or broken branches, and save other pruning measures for the second or
third year.
The belief that trees should be pruned when planted to compensate for root loss
is misguided. Trees need their leaves and shoot tips to provide food and the
substances that stimulate new root production. Unpruned trees establish faster
with a stronger root system than trees pruned at the time of planting.
| Pruning Young Trees |
| US TREE SERVICE |
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Where you make a pruning cut is critical to a tree’s
response in growth and wound closure. Make pruning
cuts just outside the branch collar. Because the branch
collar contains trunk or parent branch tissues, the tree
will be damaged unnecessarily if you remove or damage
it. In fact, if the cut is large, the tree may suffer
permanent internal decay from an improper pruning cut.
If a permanent branch is to be shortened, cut it back to
a lateral branch or bud. Internodal cuts, or cuts made
between buds or branches, may lead to stem decay,
sprout production, and misdirected growth.
response in growth and wound closure. Make pruning
cuts just outside the branch collar. Because the branch
collar contains trunk or parent branch tissues, the tree
will be damaged unnecessarily if you remove or damage
it. In fact, if the cut is large, the tree may suffer
permanent internal decay from an improper pruning cut.
If a permanent branch is to be shortened, cut it back to
a lateral branch or bud. Internodal cuts, or cuts made
between buds or branches, may lead to stem decay,
sprout production, and misdirected growth.
When pruning trees, it is important to
have the right tool for the job. For small
trees, most of the cuts can be made with
hand pruning shears (secateurs). The
scissor-type, or bypass blade hand
pruners, are preferred over the anvil
type. They make cleaner, more accurate
cuts. Cuts larger than one-half inch in
diameter should be made with lopping
shears or a pruning saw.
have the right tool for the job. For small
trees, most of the cuts can be made with
hand pruning shears (secateurs). The
scissor-type, or bypass blade hand
pruners, are preferred over the anvil
type. They make cleaner, more accurate
cuts. Cuts larger than one-half inch in
diameter should be made with lopping
shears or a pruning saw.
Never use hedge shears to prune a tree.
Whatever tool you use, make sure it is kept clean
and sharp.
Establishing a Strong Scaffold Structure
A good structure of primary scaffold
branches should be established while
the tree is young. The scaffold
branches provide the framework of the
mature tree. Properly trained young
trees will develop a strong structure
that requires less corrective pruning as
they mature. The goal in training
young trees is to establish a strong
trunk with sturdy, well-spaced
branches. The strength of the branch
structure depends on the relative sizes
of the branches, the branch angles,
and the spacing of the limbs. Naturally,
those factors vary with the growth habit
of the tree.
For most young trees, maintain a single
dominant leader growing upward. Do not
Sometimes a tree will develop double leaders
known as co-dominant stems. Co-dominant
stems can lead to structural weaknesses, so
it is best to remove one of the stems while the
tree is young. The lateral branches growing
on the sides contribute to the development of
a sturdy well-tapered trunk.
dominant leader growing upward. Do not
Sometimes a tree will develop double leaders
known as co-dominant stems. Co-dominant
stems can lead to structural weaknesses, so
it is best to remove one of the stems while the
tree is young. The lateral branches growing
on the sides contribute to the development of
a sturdy well-tapered trunk.
