Pruning

ISA Arborist Pre-exam study Course Andrew Geiser and Austin LampeJefferson 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

Broken branches

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 Rubbing branches should be removed as part

of structural pruning to prevent damage to other limbs.

Codominant stems

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.

Clearance

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.

Structural pruning

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).

Included bark

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 cleaning

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

Lion tailing

Water sprouts

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 raising

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.

Utility pruning

Pruning

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.

Pruning tools

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

Plant growth regulators