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There Is a Tree Service Standard of Care!

Certified arborist, registered consulting arborist, tree expert, tree service and landscape contractor, so many different consultants and contractors to choose from for tree care consultation and remedial work. How can you ensure your tree assets receive the state of are care they deserve? Certified arborists and tree care professionals adhere to the American National Standard Institute (ANSI) A300 tree and woody ornamental pruning standards.

There are a wide variety of tree service companies and they are not all the same. While most tree service companies have the large truck(s) with a mechanical lift bucket and chipping machine, the level of arboriculture tree care knowledge, experience and training may vary drastically between companies.

Premise liability suggests property owners have a duty of care to protect the public from a known, foreseeable tree hazard(s). A property owner who fails to protect the public from a foreseeable hazard that results in injury or property damage may be held liable in a lawsuit. To that end, residential and commercial property owners, government, industrial and recreational facilities utilize certified arborists and tree service companies to maintain their tree assets by reducing tree risk while improving tree health and appearance.

Establishing desirable structure and growth characteristics in trees begins during their juvenile stage of growth. It is vital to identify and mitigate tree defects while the tree is young and actively growing. Removing co-dominant stems, multiple or weak branch attachments, establishing scaffold structure and lowest permanent branch are training methods used while the tree is young. Training a tree during its juvenile stage provides proper structure for the tree as it grows into maturity. Trees left untrained or improperly pruned during their juvenile stage often have structural issues that create hazards as the tree ages. Once trees reach maturity, attempting to repair structural flaws such as co-dominant trunks become much more problematic or impossible to fix.

Reputable Companies Follow ANSI A300 Standards

Certified arborists and tree care professionals adhere to arboriculture management standards established in the American National Standard Institute (ANSI) A300 standards. These standards apply to professionals who provide for or supervise tree management, shrubs and other woody ornamental landscape plants. The Tree Care Industry Association (TCIA), an ANSI-accredited standards developing organization, is secretariat of the ANSI A300 standards and develops standards using procedures accredited by the ANSI American National Standard Institute (ANSI).

Prior to 1991, industry associations and private practitioners simply established their own methods and procedures for tree care. The realization a more scientific, standardized approach was needed for establishing tree care standards for the green care industry, government agencies and tree service companies led to the consensus for an official American National Standard. The purpose of the ANSI A300 performance standards is intended for government agencies, private companies, arborists, property owners, property managers and utilities for developing their own written specifications. Written specifications establish detailed plans and requirements, identifying procedures used to define the scope and guide the work. One important measure of a professional tree service is thoroughness of their written specifications and compliance to ANSI A300 standards within their contract proposal.

Basic Pruning Methods

ANSI A300 part 1 recognizes four basic pruning methods (type) for use on trees.

1. Clean: Cleaning a tree shall consist of pruning to remove one or more non-beneficial parts: dead, diseased, and/or broken branches. Cleaning is the preferred pruning method for mature trees because it does not remove live branches, this method removes dead, damaged and dying branches or stems.

2. Raise: Selective pruning to provide vertical clearance. When selectively pruning a tree for vertical clearance (raising) or horizontal clearance from a building, the desired clearance should be understood and specified.

3. Reduce: Selective pruning to decrease the height and /or spread of a tree. This method is employed to minimize risk of failure, balance the canopy, height and spread reduction, utility clearance or to improve tree aesthetics. This methods uses reduction pruning cuts on live branches from 2”-6” in diameter. Not all trees can be reduced, especially old, stressed or mature trees could decline or become stressed from this technique.

4. Thin: Selective pruning to reduce the density of small live branches. Proper thinning retains the crown shape and size and is employed to provide even distribution of foliage throughout the crown of the tree. Thinning should not exceed 25% of the foliage crown, especially in mature trees. 10-15% is the typical range for crown thinning.

Pruning Objectives

Trees should not be pruned without first establishing clearly defined objectives. There may be several reasons for tree pruning including but limited to:

• Reducing risk of tree or tree part failure
• Providing vertical and/or horizontal clearance
• Reduce shade or wind resistance
• Balance and symmetry
• Maintain tree health and aesthetics
• Improve flower and fruit production
• Improve view
• Specific objective such as directional or utility pruning

Property owner should be concerned with ensuring their trees receive pruning that meets current industry standard and arboriculture care. Pruning can be beneficial or a disaster depending on when, how, where and why applied. The owner should meet with a certified arborist to discuss and determine the tree pruning objectives. It is a fairly standard practice for tree care companies to have an ISA certified arborist on staff for sales and consultation. It is very important for companies to maintain a “firewall” to prevent a conflict of interest that could arise by their arborist recommendations for tree care.

A property owner concerned about a conflict of interest with a tree care company acting as consultant and contractor should consider using a consulting certified arborist. An independent consulting arborist, such as RDCS LLC, has no potential for conflict of interest or financial considerations influencing tree care decisions. Opinions and recommendations are based on a combination of experience, current industry science and standards. The owner can utilize the consulting arborist report as the basis of bidding the work to several tree service companies. The owner may choose to use the consultant to assist in reviewing the tree service company’s proposals that should include ANSI A300 terminology in the proposal.

Pruning Specifications

As previously discussed, a specification is a document stating a detailed, measurable plan and procedures used to define and guide the work. There are numerous specifications used by tree care companies to define the scope of work in a tree care proposal. ANSI A300 pruning standards are not specifications, they are performance standards established for industry professionals to use as a guide to writing individual job specifications for each project they work on. Each specification should be clearly written, detailed and contain measurable criteria.

Minimum pruning specification requirements should include:

• Identify and state which trees are to be pruned.
• A statement that all work shall be performed in accordance with ANSI A300 pruning standard and ANSI
Z133.1 safety standard.
• Include clearly defined pruning objectives.
• Specify the pruning methods to be performed to meet the objectives.
• State the size specifications of the minimum and/or maximum branch size to be removed.
• Specify the maximum amount (percentage) of live tissue to be removed.

How to Identify a Reputable Tree Service

A professional tree care service company should have a valid contractors license, in California a D-49 is the specialty license number for tree care service contractors and C-27 for landscape contractors. Make sure the service has an ISA certified arborist (International Society of Arboriculture) on staff who has visited the site, inspected the trees and wrote the job specifications for the project.

The written proposal should be examined for ANSI conformance and specifications; their proposal should be in two sections.

I. General:

The first section should contain all aspects of the work to be performed. Work should be generally documented but does not need to be detailed in this section. Included in this section should be the statement: “All work shall be completed in compliance with ANSI A300 and Z133.1 standards”. This clause means safety, inspections, pruning cuts etc. will be adhered to. Other general items such as work hours, dates, traffic, access deliveries etc. should be included in this section.

II. Details:

This section should contain the clear and measurable criteria, what are known as the deliverables to the client. These details define the scope and extent of the work and should be highly detailed.

1. Define the objectives. The objectives originate from the owner but should be clarified, defined and refined with assistance from the arborist. The arborist must be able to clearly state what is going to be done to achieve the objectives.
2. State the type of pruning methods used to achieve the objective.
3. State the location within the tree(s) the work methods will take place.
4. State the density, which is the amount or volume of the tree parts to be removed.
5. State the size or range of sizes of cuts utilized to remove the volume specified.

Did You Receive Professional Service?

Unfortunately, there are many unlicensed and unqualified people representing themselves as tree professionals. Even tree care companies are not immune from making mistakes. An improperly trained or unsupervised employee left unattended for even a short time may accidentally cut limbs not defined in the scope of work. To ensure your tree assets are receiving the care defined by industry standards, use a tree care company that states in writing all work is performed in accordance to ANSI A300 pruning and Z133 safety standards. Carefully review work proposals from tree service companies, note whether they have provided general and detailed specifications. Confirm your pruning objectives and the pruning methods to achieve those objectives are clearly defined. Do not use a tree or landscape contractor who provides either a verbal or boilerplate contract. Avoid unlicensed individuals and gardeners who do not have the expertise to properly prune your trees or woody ornamentals. Once a limb is cut, it is gone forever, restoring poorly pruned trees can take several years, in some case if the tree is improperly pruned or topped, the tree form may be lost forever and can never be properly restored.

Over time, trees can grow into valuable assets for your property. Remember trees are living organisms and just like humans, they require care and maintenance. You most likely would not seek medical care from an unlicensed or untrained individual. Avoid the cheaper prices offered by the guy with a chainsaw and pickup truck, or even tree service companies that do not provide a job specific written set of specifications with their proposal. Protect and enhance your tree assets by using an ISA certified arborist or ASCA (American Society of Consulting Arborists) registered consulting arborist (RCA). In doing so, your trees will receive the highest arboriculture industry standards available.


American National Standard for Tree Care Operations: Tree, Shrub, and Other Woody Plant Management-Standard Practices (Pruning), ANSI A300 (Part 1)-2008. Tree Care Industry Association, 2008.

Best Management Practices, Tree Pruning (Revised 2008). Companion publication to ANSI A300 Part 1. Edward F. Gilman & Sharon J. Lilly, International Society of Arboriculture, 2002.

By Rappoport Development Consulting Services LLC
Certified and Registered Consulting Arborist, Landscape, Horticulture & Land Development Expert
ABOUT THE AUTHOR: Jeremy Rappoport
Jeremy Rappoport is President of Rappoport Development Consulting Services LLC, located in San Diego, California. RDCS LLC provides expert witness consulting services for attorneys and insurers and environmental consulting services as a certified tree arborist and tree risk assessor, licensed landscape contractor, California plant expert and professional horticulturist, and land development professional.

Copyright Rappoport Development Consulting Services LLC

Disclaimer: While every effort has been made to ensure the accuracy of this publication, it is not intended to provide legal advice as individual situations will differ and should be discussed with an expert and/or lawyer.For specific technical or legal advice on the information provided and related topics, please contact the author.

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