Decision Making for Pruning Trees

Denice Britton CalTLC Consulting Arborist Auburn and Napa, CA [email protected] OVERVIEW OF PRESENTATION

Response of Trees to Pruning Pruning Standards Define Objectives Manage Risk – Weight Reduction, Crown Reduction  Manage Health – Crown Cleaning  Develop or improve structure  Restoration Pruning  Provide Clearance  Manage size or shape  Manage Production  Rejuvenate – shrubs or trees  Management Wildlife habitat Select System – Natural in almost all cases  Application to Tree Work Tree Responses to Pruning

Dwarfing – Removal of Food Factories, or Photosynthetic surface area: Leaves Shoot Elongation – Fewer buds to spread out stored sugars to, so individual shoots may be invigorated Sprouting – When too much foliage is removed Decay – When poor cuts are made that remove the ends of large branches, expose wood through sun burn, or result in limb breakage  (CODIT) Compartmentalization of Decay in Trees Dwarfing - 2004 2010 Reduced size in comparison, Spring 2013 Dwarfing -

2004 – 40% of base 2013 – 20% of base Shoot Elongation

Removing competing stems will encourage the one remaining to grow longer Stored sugars have fewer stems to feed Prune to leave branches that grow in the direction you want the branch to grow – branches do not change direction! Removing lower branches encourages height growth on trees Sprouting of new foliage • Heading cuts produce copious sprouts • Heading cuts remove the barrier zone against decay • Weakly attached sprouts , easily break off the decaying stub • Once this occurs, the tree needs more care • Creates a more expensive situation for the client CODIT

Compartmentalization Of Decay In Trees Poor pruning practices lead to decay When injuries expose wood, the tree begins to decay, Trees can only add new tissue outside the old Decay does not progress into the new wood formed after the injury, unless new injuries occur Decay in Limbs and Trunks

Concept of CODIT describes bark wounds Applies to branch cuts Branches have a barrier zone to prevent decay from entering the main stem Pruning needs to preserve this barrier zone Flush cuts lead to decay because they remove the Barrier zone Standards say “Cuts shall be outside the Branch Bark Ridge and Collar” – confine pruning to the branch, not the stem Heading cuts removes the barrier at the terminal end of the branch – exposing the entire limb or trunk to decay

Flush cuts lead to trunk decay Decay in Trunks

Hollows rarely influence vigor Thickness of wood outside the hollow influences safety of the limb or trunk Decay helps keep trees flexible Decay allows tree to break easier Decay in Trunks Requires Weight Reduction Pruning American National Standard for Tree Care Operations -

Tree, Shrub and Other Woody Plant Maintenance - Standard Practices A300 – 1998, 2001, 2008, 2017 Pruning Guidelines Safety

Tree Maintenance Shall only be performed by Qualified Tree Workers Documented Training Shall not take precedence over Safe Work Practices Shall comply...OSHA and ANSI Z133.1 (2017) Pruning Requires Climbing Skills

Climber Safety

Tree Inspection - REQUIRED:  Before Climbing  During Operation  Reporting Conditions Found Root Collar examination is Included Look for defects – those not corrected must be pointed out to supervisor or owner

Tools and Equipment

Sharp and Clean No Anvil Type Pruners No Hooks or Gaffs, except for removals Work Practices shall not injure the tree Pruning requires skilled use of equipment. Sometimes large limbs must be removed after breakage.

Consider leaving stubs for wildlife if they will not break again. Proper pruning cuts on large trees Leaving stubs

• Cut was made too flat • Callus can’t grow over old wood • Decay enters original stem • If cut properly, decay should be confined to the branch trace, and not spread into the parent stem When not to remove live foliage

Improve Cultural Conditions ANSI Standards – 2017 Update

Identify Reasons • Define Objectives • Reduce Risk • Manage Risk • Improve Health • Manage Health • Develop Structure • Develop Structure • Provide Clearance • Prevent interference with • Manage size the built environment • Improve aesthetics • Manage Fruit and Flower production • Manage Wildlife Select Pruning System A natural system (of pruning) is preferred. It should maintain the tree’s natural characteristic size and growth pattern, and leave the tree in a natural form A Crown Reduction system reduces the height and/or spread of a tree. Using reduction cuts, prune limbs back to a branches that are the same size as that being removed, or at least 1/2 the size of the limb being removed. Heading cuts should ONLY be made to accomplish specific pruning objectives, such as:

. Initiation of a pollarding system . Structural development in young trees . Restoration or rejuvenation when the remaining stub will likely sprout new growth . If a stub has been created by large branch breakage and no . interior limb is present, the broken stub can be retained . for wildlife habitat. . Extensive branch breakage is occurring in vigorous trees Specifications – not just for bids, but for Work Orders

• After System is defined, Specify: • Parts to be removed (dead, diseased, crossing) • Pruning amount (Remove 30%) • Location on tree (the outer 15 feet of the limb or branch) • Cuts to be used (removal or heading cuts) • Size range (2-4”) • Debris removal • Time frame Manage Risk Crown Reduction System

Heritage Elm • Extensive decay in limbs • History of branch breakage • Reduce some limbs • Reduce the number of redundant limbs in the outer 15-20 feet of the branches • Making larger cuts to reduce decay that has resulted from breakage • Increase frequency of inspections and pruning Detailed Pruning Specifications

• Prune to remove the dead branches with a diameter of 1 inch or larger from the tree. • Prune to reduce the weight of over-extended branches by approximately 20 to 25%. This can be accomplished with branch removal cuts, reduction cuts and heading cuts making the smallest diameter cuts possible to accomplish the desired crown size and branch leverage weight. • Prune to reduce the weight of the smaller branch with included bark by 25%, and the long, over-extended branches by approximately 30 to 40%. Using branch removal, reduction, or heading cuts to remove redundant (parallel, crowded) branches that are 2” to 6” in diameter, in the outer 15’ of the canopy. Manage Risk – Natural System

Manage Risk Weight Reduction-Vigorous oak over roof Extensive weight on all limbs Start of process

Up he goes Almost there After Pruning

Extensive weight reduction as crown reduction without disfigurement Improved safety for several years Final results of pruning Manage Risk Large tree over Glass-fronted Home

Tree dwarfs the large home Large dead and heavy limbs Health and Structure Concerns

Root collar is buried Bark is buckling After Pruning

Natural Pruning System Natural form Before After B-2 Manage Health (Crown Cleaning)

Remove Dead, Diseased or Broken branches Specify Size and location of branches to be removed On trees that are declining – remove MINIMAL amount of live foliage

B-3 Develop or Improve (of Young Trees) • Central leaders provide the Strongest Structure • Choose most upright • Cut back other limbs that may compete • Simplify structure • Prune to outside facing buds Develop or Improve Structure

Establishing the main Scaffolds Removal cuts remove branches to the trunk Used to distribute permanent limbs around and up and down the trunk Limbs may still be too close together Structural Development

Thinning or reduction used to subordinate side limbs that are temporary Slowing them down allows a better branch bark ridge to form You can slow down the growth by removing a large amount of foliage near the tip. Looking for Scaffolds

Established Central Leader Low branches temporary Scaffolds should be less than ½ the size of the trunk at attachment Remove foliage to improve branch to trunk ratio ANSI Standards Structural Development

Central Leader at top of tree Scaffolds will need to be reduced in number Remove only 25% at any one pruning on slower growing trees B-4 Provide Clearance

At least ½ of the foliage should be on branches that arise in the lower 2/3 of the tree 90% of the foliage in this tree arises on branches in the upper 1/3 of the tree Crown Raising to provide clearance

Provide vertical clearance underneath the canopy of a tree Specify limbs to be elevated Specify height of elevation Leave ½ foliage in lower 2/3 of tree Shape away from building Small tree, still needs to be shaped Will be done over time

Codominant branch to be reduced Retain low foliage for screen Heading and removal cuts used B-5 Manage size or shape – Crown Reduction Selective pruning to decrease the height and/or spread of a tree (Shaping) Specify branches to be shaped and the amount of clearance to obtain Consideration should be given to the tree’s ability to tolerate this type of pruning Results in MORE Long-Term Maintenance B-5 Manage size or shape Crown Reduction

Restoration Pruning Retrenchment - Preservation: Veteran Trees

Reduce length and weight on long heavy limbs Restore foliage by keeping new limbs shorter Only use this form of pruning when the tree is in fact becoming a veteran and has already lost 2 or more large limbs Some suggest making veterans trees out of perfectly good, young trees View or Vista Pruning GENERAL APPLICATIONS TO ARBORICULTURE Consider Growth Cycles when Prescribing Pruning Pruning in early summer reduces growth the most Winter pruning can cause shoots to elongate Remove only dead branches on trees that are already thin, don’t remove foliage Remove foliage on heavy trees in the outer canopy Remove more than 25% on specific limbs, if needed Improve health by improving cultural conditions in which the tree is growing: mulch, irrigation, fertilization