PROPER PRUNING TECHNIQUES

    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
    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.
    Pruning Tools
    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.
    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. 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
    For most young trees, maintain a single dominant leader growing upward.
    Do not prune back the tip of this leader. Do not allow secondary branches
    to outgrow the leader. 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. 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.
    Wound Dressings
    Wound dressings were once thought to accelerate wound closure, protect
    against insects and diseases, and reduce decay.
    However, research has shown that dressings do not reduce decay or speed
    closure and rarely prevent insect or disease infestations. Most experts
    recommend that wound dressing not be used. If a dressing must be used
    for cosmetic purposes, use a thin coating of a material that is not toxic to
    the plant.