PruningISA Arborist Pre-exam study Course Andrew Geiser and Austin Lampe Jefferson City Parks, Recreation, and Forestry
Objectives Know why, when and how to prune Understand Compartmentalization and its relationship to the branch collar Know the proper procedures and techniques used in pruning Understand how trees respond to proper and improper pruning
Why do we prune? To remove broken, dead, & diseased branches Improve the structure of trees and reduce the risk of future failures Remove rubbing branches Remove co-dominant stems Provide clearance for sidewalks, roads, and utilities
Pruning to reduce hazards Removing broken and dead limbs. Broken and dead limbs can be a hazard depending on the trees location. Trees in high traffic areas (pedestrian and vehicular) usually have more targets where as trees in low traffic areas pose less of a hazard.
Hazard Hazard tree in high traffic area
Structural Pruning Defined as: Pruning that influences the orientation, spacing, growth rate, strength of attachment, and ultimate size of branches and stems resulting in a strong tree
Rubbing branches Rubbing branches should be removed as part of structural pruning to prevent damage to other limbs.
Codominant stems Codominant stem: A stem growing at about the same rate, and with nearly the same diameter, as another stem originating from the same union.
When should we prune What is the desired result? Maximize growth: early spring Minimize risk of pest and decay: dormant season Minimize effects to flowers and fruit: immediately after flowering Time of year may not always be an option. Storm damage Hazard mitigation
Branch Collar A swelling at the base of a branch where it joins the trunk, or larger branch, resulting from overlapping trunk and branch tissue.
Branch Protection Zone This is a thin zone of starch-rich tissue at the base of a branch where chemicals are deposited to retard the spread of discoloration and decay. Pruning in this zone allows for compartmentalization of the wound.
Branch Bark Ridge
Pruning procedure and techniques All pruning should be done in accordance with ANSI A300 standards. The three cut method should be used when removing a branch. Reduction cut is used when reducing a limb or stem.
Three cut method
Reduction cut Removal of stem to a smaller branch (at least 1/3 diameter) that will assume the terminal role.
Main types of pruning Structural pruning Crown cleaning Crown thinning Crown raising Crown reduction Crown restoration Utility pruning
Structural pruning Pruning to remove dead, broken, damaged branches Select a dominate leader or multiple strong leaders in ornamentals and fruit trees. Competing stems should be subordinated (Removing the terminal, typically the end portion of a branch or stem to slow growth rate so other portions of the tree grow faster).
Structural pruning Select and establish the lowest permanent branch (Branches that will remain on the tree for many years, perhaps until maturity). Select and establish scaffold branches (Branches that are among the largest in diameter on the tree that will provide the structure of the tree). Scaffold branches should be well spaced, both vertically and radially.
Structural pruning Select and subordinate temporary branches (Branches that will remain on the tree for only a short period). Why do we leave these branches? Energy production Strengthen the trunk Protection from the sun Protection from mechanical injury
Structural pruning As the trunk gains strength, temporary branches can be gradually removed. 25% rule should be followed, where no more than 25 percent of the canopy should be removed in one year.
Codominant stems Codominant stems are forked branches of nearly the same size in diameter and lacking a normal branch union. Frequent site of included bark (bark that becomes embedded in a crotch as the two branches grow and develop causing a weak point).
Good union vs. Codominant
Crown cleaning Removal of dead, diseased, rubbing and broken branches. Cleaning can be done at almost any time of the year and on any age of tree.
Crown thinning Select removal of lateral and parallel branches, especially from the edge of the canopy. Reasons we may thin the canopy Improve light penetration and air movement Thinning may reduce risk of storm damage Reduce limb weight Show off attractive bark or trunk form
Crown thinning Care must be taken to not over thin a tree The removal of excess interior branches and foliage and leaving most of the foliage at the end of the canopy is referred to as lion tailing. The over thinning of the interior growth and lower branches has many negative effects. Weak branches Reduces stored energy reserves Increases damage from storms
Crown thinning Production of water sprouts (Stems arising from the interior branches often growing upright and vigorously) Even death of the tree may result Never remove more than 25% of the entire crown
Crown raising Select removal of branches to provide vertical clearance under the canopy. Raising should be done gradually over a period of time. Never remove 1/3 of the crown Never remove a branch that is ½ the size of the diameter of the trunk
Crown reduction Select removal of branches to decrease height or spread on entire tree. Some reasons to reduce the canopy might be Reduce weight to reduce failure potential Direct growth away from an object of structure Open a view Again make sure to follow the 25% rule and the 1/3 rule.
Crown reduction Do not mistake this as topping. Reduction cut
TOPPING Topping or heading back is the cutting back of limbs more than two years of age to buds, stubs, or laterals not large enough to assume apical dominance.
TOPPING This is topping and is not recommend!
Crown restoration Process of improving the structure of a tree that was previously topped, over-thinned, damaged, or vandalized. This process is not a quick fix. It can, and probably will, take several years. The process involves removing some sprouts, all stubs, and dead branches. One to three sprouts are selected to become permanent branches and to reform a more natural appearing crown. Restoration will not make the tree what it once was.
Utility pruning The removal of branches or stems to prevent the loss of service, prevent damage to utility equipment, avoid impairment, and uphold the intended usage of utility facilities. Only qualified line clearance trimmers should engage in line clearance work. May be necessary to prune outside the scope of landscape pruning guidelines, but when practical cuts should be made, to A300 standards.
Specialty pruning Espalier, Pollarding are both conducted to create special aesthetic effects.
Specialty pruning Espalier is a combination of cutting and training branches that are oriented in one plane, usually supported on a wall, fence or trellis. Used for fruit trees when space is limited Pollarding is a training system that involves severe heading the first year, and sprout removal annually or every few years to keep large trees to a modest size or to maintain a formal appearance. Internaodal are cuts made at a specific locations to begine the pollarding process
Wound dressings Once thought to accelerate wound closure and reduce decay, but research does not support this. May be beneficial in reducing borer attack, oak wilt, or sprout formation. May inhibit compartmentalization. If used, apply a light coating of a non- phytotoxic material.
Pruning tools Use tools that are adequate for the size of cuts being made. In some instances, sterilization of tools between trees and even between cuts maybe necessary.
Plant growth regulators Plant growth regulators are substances, effective in small quantities, that enhance or alter the growth and development process of a plant. Used to increase or decrease normal growth, flowering or fruiting of plants May also be used to reduce the production of water sprouts on trees
Plant growth regulators May be applied in several ways Foliar spray Basal bark spray Soil applied Injection of the tree