TREE MAINTENANCE AND SPECIFICATIONS

Pruning cuts shall be made in accordance with the latest applicable ANSI A300 pruning standards. All arboricultural work shall be planned and performed by trained and competent workers in accordance with applicable OSHA, state, and local requirements, and ANSI Z133-2026 Safety and Health Requirements for Arboricultural Operations.

GENERAL PROCEDURES AND TECHNIQUES

The foliage removed shall be taken primarily from the outer edge of the canopy, not from the interior. No more than 20% of the foliage shall be removed from any tree unless otherwise specified. Dead branches greater than 1.5 inches in diameter (measured at the base of the branch) shall be removed from the canopy of all trees that are pruned. When removing a dead branch, the final cut shall be made outside the collar of the living wound wood tissue. If the collar has grown out along the dead branch stub, only the dead stub shall be removed; the living collar shall remain intact and uninjured regardless of its length. Live branches under 1.5 inches in diameter should generally be retained unless removal is needed for clearance, access, structural pruning, tree health, risk reduction, or the specified pruning objective. No live branches or stems greater than 3 inches diameter should be removed from the tree unless otherwise specified.

When removing a live branch at its point of origin on the trunk or from a parent branch, the final pruning cut shall be made in branch tissue just outside the branch bark ridge and collar. No stubs shall be left. (A stub is the remaining branch tissue to the outside of the collar and branch bark ridge.) Live crown ratio should be at least 60% when pruning is completed meaning that no more than the lower 40% of the tree shall be clear of branches.

Removal and reduction cuts shall be used, and not heading cuts.

Never top a tree. Instead, prune to its natural shape.

Safety and Worksite Requirements

Before pruning begins, the arborist in charge shall review jobsite hazards, work procedures, job assignments, special precautions, PPE requirements, and communication methods with affected workers. Crews shall assess tree condition, identify electrical hazards, establish drop zones before branches or equipment are dropped or lowered, and keep unauthorized people outside active drop zones.

Workers shall use PPE appropriate to the pruning task, equipment, and worksite hazards. This may include head protection, eye protection, hearing protection, footwear, fall protection, and chainsaw-related protection where required.

Trees near energized electric supply lines shall be assessed before work by a qualified arborist trained in electrical hazard recognition. Crews shall maintain the applicable minimum approach distance based on voltage, worker qualification level, and work conditions. If the required distance cannot be maintained, work shall stop until an electrical hazard abatement plan is coordinated with the electrical system owner/operator.

Pruning Treatment Definitions

PRUNING LEVEL I – CLEARANCE PRUNING

Standard distances: 14 ft above road; 10 ft from roof; 8 ft above walkway; 5 ft from buildings. Will not prune within 10 ft of overhead power lines.

PRUNING LEVEL II – CLEARANCE & CROWN CLEAN

Includes Level I. Standard clearance distances. Prune deadwood, diseased/dying, and crossing branches over 2”. Prune out lowest sucker growth.

PRUNING LEVEL III – SAFETY & STRUCTURE

Includes Level I & II. Standard clearance distances and crown clean. Prune to address structural defects where possible, which may include hazard reduction pruning, removing deadwood, clearance pruning, removing lowest sucker growth, and end weight reduction. Prioritize needs within allotted time.

For Young Tree (under 6″ DBH):

  • Begin to establish a central leader on excurrent trees.
  • Subordinate temporary lower branches.
  • Create scaffold spacing.

For Adolescent trees (6-18″ DBH):

If excurrent growth:

  • Structure prune to establish central leader.
  • Establish the lowest permanent branch.

If decurrent growth:

  • Establish the lowest permanent branch.
  • Reduce end weight.

For Mature trees (Over 18″ DBH):

  • Reduce end weight.
  • Crown Clean & clearance.
  • Remove lower sucker growth.

PRUNING LEVEL IV – HEAVY CROWN REDUCTION, THINNING & CLEARANCE

Heavy crown reduction, thinning, and clearance pruning to reduce canopy size, end weight, and wind-sail. Live foliage removal may exceed standard industry practices and allow up to 70% canopy reduction as specified in notes. This does not conform to ANSI A300 / ISA pruning standards and is only performed at the client’s request.

CLEARANCE PRUNING

Use reduction cuts or removal cuts to increase clearance from buildings, roofs, lights, sidewalks, roads, and other specified targets.

Standard clearance specifications:

  • Buildings: 5 ft clearance
  • Roof: 10 ft clearance
  • Walkway: 8 ft vertical clearance
  • Roads: 14 ft vertical clearance

Work near energized electric supply lines shall follow the electrical hazard requirements listed above.

CROWN CLEAN

Crown clean pruning includes the removal of dead, diseased, dying, broken, rubbing, or crossing branches over 2 inches in diameter. Prune out the lowest sucker growth. Include standard Level I clearance pruning specifications.
Use directional pruning where possible so future growth is directed away from buildings, lights, and other specified targets.
Do not strip out interior foliage or leave live growth only at branch ends.

 

CROWN RAISE

Prune or remove the lowest branches to provide vertical clearance. The live crown ratio should be at least 60%. Leave small-diameter branches on the lower trunk where appropriate to help protect the tree. Vertical clearance height should be specified in the treatment notes. Include standard clearance pruning specifications.

CROWN REDUCTION

Prune to reduce both height and spread of the canopy by removing the end portion of branches with reduction cuts to appropriate lateral branches. Include deadwood over 2 inches DBH and clearance pruning.

CROWN THIN

Selectively prune to reduce the density of live branches. Do not over-prune interior branches. The percentage of foliage removed is not to exceed 25% unless specified by the client. Include deadwood over 2 inches DBH and clearance pruning.

“Lions-tailing” shall not be performed. (Lion-tailing is the practice of removing only the inner branches closest to the trunk on a parent branch and leaving the branches located toward the end of the parent branch.)

Appropriate thinning removes small branches from the edge of the canopy (right).

Inappropriate thinning removes only interior and lower branches (left).

PALM PRUNING

All large-growing palms should be pruned to remove dead fronds, fronds below the specified pruning angle, fruit, and seedpods.
NorCal: Prune fronds below horizontal, 10 and 2. Remove fruit and seeds. Create clearance.
SoCal: Prune fronds above horizontal at a 45 degree angle, 9 and 3. Remove fruit and seeds. Create clearance.
For date palms, prune at horizontal, 10 and 2.
Palm pruning work shall account for the unpredictable distance and direction of falling fronds and skirts. Crews shall establish an expanded drop zone where needed, and climbing arborists shall use palm-specific precautions when working around frond skirts.

RISK REDUCTION PRUNING

Risk reduction pruning is based on visible tree conditions and the pruning objective. Where significant defects, decay, or failure concerns are present, a more detailed tree risk assessment may be needed before work begins.

STRUCTURAL PRUNING

The structure of a tree can only be corrected in the younger stages of growth. If the tree is mature, then Risk Reduction pruning may be more appropriate (see definition above).

The goal of structural pruning is to increase the structural integrity of a tree and encourage a healthier and more stable tree in the long-term.

For Excurrent Tree structures:

  • Establish a central leader and develop for a strong dominant leader by shortening competing stems and branches that compete with the stem that will make the best trunk.
  • Use reduction cuts to shorten stems back to later branches.
  • Keep main branches less than 1/2 the DBH of the main trunk.

For Decurrent Tree structures:

  • Prune to create proper spacing between lateral branches to reduce future competition.
  • Reduce end weight on long lateral branches.
  • Establish the lowest permanent branch if it has not yet been established.

Co-dominant Leaders and Stems

Co-dominant leaders are considered to be two or more branches, trunks, or leaders of approximately the same size, originating in close proximity to one another.

Due to the recognized potential hazards associated with the co-dominant leaders, the subordination (shortening using a reduction cut) or removal of one side of a co-dominant leader is the primary objective. The main leader should not be subordinated, headed or removed.

YOUNG TREE TRAINING

Young tree training may arguably be the most important stage of pruning. It sets up the tree for a life-long growth structure.

Train young trees for good form and structure by developing a strong dominant leader. Shorten stems that compete with the leader using reduction cuts.

Shorten vigorous, aggressive branches in the permanent nursery canopy using reduction cuts. If two vigorous branches are growing opposite one another, shorten one (lower right branch ‘a’) more than the other (lower left branch ‘b’). The one shortened the most will grow the slowest. The other one will become the one main branch at this point.

Health and Structure Ratings

These ratings are based on visible conditions observed at the time of inspection and are intended for field classification. They do not replace a formal tree risk assessment when site conditions, targets, decay, structural defects, or client concerns require a more detailed evaluation.

Note: In order for a tree to be category 5, it must possess all 3 conditions. In order for the tree to fall under categories 4-1, it only needs to satisfy 1 or more of that category’s conditions.

5-Good:

  • No visible defects in crown, trunk, roots.
  • No signs of insects or disease
  • Canopy full and balanced

4-Fair:

  • Minor defects in crown, trunk, roots
  • >30% Bark missing from the trunk
  • No signs of insects or disease
  • Canopy full and unbalanced

3-Poor:

  • Unequal weight distribution due to trunk lean
  • Full canopy lacking
  • Trunk displays signs of wood deterioration
  • Crown root area displays signs of wood deterioration
  • Light insect and disease symptoms
  • Some dead limbs

2-Very Poor:

  • Trunk area decayed >30% of tree’s x-section
  • Decay in >30% of limb’s x-sectional area
  • Split trunk
  • Canopy dieback and unbalanced
  • Branch attachment area displays signs or symptoms of wood deterioration
  • Extensive portions of root system cut or root rot
  • Extensive insect and disease symptoms

1-Recommended Removal:

  • Dead tree
  • Crown root area decayed more than 30% of tree’s cross-section
  • More than 30% crown dieback
  • High risk of limb or trunk failure
See Glossary of Terms