Pruning of trees requires:
- Knowledge of when, why and how to initiate the desired pruning techniques.
- Years of experience in the field.
- Skills must be developed and refined to be able to manipulate the appropriate concepts and tools needed for pruning.
- An understanding as to how the tree evolved from a seed.
- A great respect for trees, the time it takes for its growth, its size, strength and awesome beauty.
- Ability to “see” the future growth, or sense that certain twigs or branches will develop in ways that would not fit well with the tree’s overall function… so they can be trimmed to redirect development.
Why do we need to prune trees?
Trees need pruning for several reasons:
- Improves natural form and appearance.
- Improves branch spacing.
- Strengthens branch attachment.
- Invigorates or slows branch growth rate.
- Improves stability by reducing wind resistance.
- Removes dead, weakened, injured, diseased or insect-damaged branches.
- Increases lighting to the interior.
- Reduces hazard potential.
Practices Pruning Standards In Accordance with the International Society of Arboriculture(ISA)
Trees and other woody plants respond in specific and predictable ways to pruning and other maintenance practices. Careful study of these responses has led to pruning practices which best preserve and enhance the beauty, structural integrity, and functional value of trees.
In an effort to promote practices which encourage the preservation of tree structure and health, the ISA Certification Committee has established guidelines, recognizing that trees are individually unique in form and structure, and that their pruning needs may not always fit strict rules. The Certified Arborists must take responsibility for special pruning practices that vary greatly from these Standards. The following is a summary of the ISA Standards
- Removes a branch at its point of attachment or shortens it to a lateral.
- Opens up a tree removing primarily dead, crossing or diseased branches.
- No more than one-third of the live foliage should be removed.
- May reduce a tree’s height.
- Distributes resultant invigoration throughout a tree and helps retain the tree’s natural shape.
- Can safely be accomplished anytime of the year.
- Preferred in tree pruning.
- Removes a branch to a stud, a bud or a lateral branch.
- Should be seldom be used because hearty, weekly attached upright sprouts are forced just below such cuts, and the tree’s natural form is altered.
- May result in stubs dying off or producing only weak sprouts.
- Should be clean and smooth with the bark at the edge of the cut firmly attached to the wood.
Large or Heavy Branches
- That cannot be thrown clear, should be lowered on ropes to prevent injury.
Wound dressings and tree paints
- Have not been shown to be effective in preventing or reducing decay.
- Are not recommended for routine use when pruning.
Types of Pruning – Mature Trees
- Removal of dead, dying, diseased, crowded, weakly attached, and low-vigor branches and water sprouts from a tree crown.
- Includes crown cleaning and the selective removal of branches to increase light infiltration and air movement into the crown.
- Stimulates and maintains interior foliage, which in turn improves branch taper and strength.
- Reduces weight of important limbs.
- Emphasizes the structural beauty of trunk and branches while improving the growth of plants beneath the tree by increasing light infiltration.
- Used to reduce the height and/or spread of the tree.
- Thinning cuts are most effective in maintaining the structural integrity and natural for of a tree and in delaying the time when it will be pruned again.
- The lateral to which a branch or trunk is cut should be at least one-half the diameter of the cut being made.
- Improves the structure and the appearance of trees that have been topped or severely pruned using heading cuts.
- One to three sprouts on main branch
- stubs should be selected to reform a more natural appearing crown.
- Selected vigorous sprouts may need to be thinned to a lateral, or even headed, to control length growth in order to ensure adequate attachment for the size of the sprout.
- Restoration may require several pruning over a number of years.
- Removes lower branches of a tree in order to provide clearance for buildings, vehicles, pedestrians, and vistas.
- At least one-half of the trees foliage should be left on branches that originate in the lower two-thirds of its trunk to ensure a well-formed, tapered structure and to uniformly distribute stress within a tree.
- When pruning for view, it is preferable to develop “windows” through the foliage of the tree, rather than to severely raise or reduce the crown.