Consulting Services

Casualty Appraisals

Appraisals are needed when trees and landscape plants are damaged or destroyed. Appraising trees and shrubs is both objective and subjective. The definitive authority for appraising landscape plants is the Guide for Plant Appraisal. This guide is authored by the Council of Tree & Landscape Appraisers. Now in its 9th edition, it is published by the International Society of Arboriculture.

Several methods for plant appraisal are examined in this guide. The most commonly used methods are Replacement Cost, Cost of Cure, and Trunk Formula.

In both Cost methods, value is determined using current plant and installation costs necessary to restore the site to a pre-casualty condition. Additional monetary damages are sometimes included if there are insufficient materials available on the market to provide adequate site restoration.

The Trunk Formula method uses an extrapolation of replacement costs for trees too large to replace or with trunk diameters nine inches or larger.

Appraisals, as defined by the American Society of Consulting Arborists, must be impartial, independent and objective.

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Expert Witness

Expert witnesses are needed when specific or technical information and expertise is necessary in decision making. Such a specialist provides expert opinion about tree value, longevity, risk assessment, plant identification, etc.

Technical jargon is presented in easy-to-understand language.

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Tree Preservation & Retention

Many municipalities require the preservation of a specific quantity and size of tree to be preserved during and after site development. Some even regulate the removal of trees on private property.

Preserving trees during development and construction requires planning, adequate root-zone, trunk and canopy protection, and that the appropriate trees be selected for preservation. It is not always the tallest or oldest tree that should be selected for retention.

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Tree Risk Assessment

Risk is a measure of how likely it is that some event will occur.

Risk Assessment is the investigation of observable phenomena and their implications to arrive at an estimate of risk.

Risk Management is the identification, assessment and prioritization of risk followed by an economical application of resources that minimizes, monitors and controls the risk levels identified.

Hazardous Tree is a tree that has been assessed as having characteristics that make it an unacceptable risk for continued retention.

The tree risk assessment is a systematic process that reviews risk factors and ranks them into risk categories.  A hazard tree exists when the sum of the risk factors assessed equals or exceeds a predetermined threshold of risk.  Below that threshold, the tree is not considered to be a hazard.

Targets are people and/or property within striking distance of a tree or its component parts. A risk assessment is focused on the relationship between the location of the tree on a site, and the use of the site by people, buildings, or other structures.  If there is nothing of value that would be damaged in the event of a failure, then there is no target, and therefore, no hazard. Regardless of the risk of a tree to fail, without a target it is not a hazardous tree.

All trees pose some degree of risk all the time. When a target does exist, the assessment process provides a means to evaluate the:

Each of these three components is assigned a number to derive an overall risk rating.

Favero Greenforest is a Certified Tree Risk Assessor through Pacific Northwest Chapter of ISA. This certification is also known as TRACE (Tree Risk Assessment Course and Examination), and is the standard for tree risk assessment. 

Risk can never be totally eliminated from any situation.  This issue, regarding trees, is not one of avoiding risks altogether but rather one of managing risks in a sensible way.  Risk management requires two things: a modicum of common sense and information about the character and magnitude of the risk.  The risk assessment provides that information to the risk manager.

Risk management is solely the responsibility of the landowner.  The arborist does not assume any liability for the subject tree and does not represent the transfer of such for any risks associated with the tree.  Trees are biological systems and change over time; therefore, risk management is ongoing, and future inspections are required. They are the responsibility of the risk manager/landowner to initiate.

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Tree Pest Diagnosis

Accurate diagnosis of plant pests is essential to provide a meaningful prognosis and useful treatment options.

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Landscape Monitoring

This service provides regular inspections, assessments and reporting for property managers and landscape committees lacking the training and expertise to diagnose pests, assess problems and write maintenance specifications. Each inspection is followed by a report that provides documentation of current problems and recommendations for solving them. The report is concise and clear. The opinions and recommendations are independent and objective.

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Pruning Specifications

The pruning of trees, shrubs and other woody plants is standardized by American National Standards Institute. These standards are referred to as ANSI A300-1995. They were developed by industry leaders through consensus and due process.

The use of professional standards provides uniformity in bids and estimates that include tree pruning. They create the possibility of professional, uniform care through pruning.

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Report Writing

Diagnosing the problem or assessing the failure risks is sometimes not enough. Most people who hire consulting arborists must make decisions that affect others. A written report is not only documents a situation, but is record of the opinion and recommendation of the consultant.

Registered Consulting Arborists have attended intensive training courses in report writing, and have had their working reports reviewed and graded by a committee of peers.

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On-Site Training

Training in the field or in the workplace provides new skills and valuable information for employees. An investment like this not only increases productivity, but can also be a source of continuing education credits for various certification requirements.

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Consulting Services:

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Greenforest, Inc.
phone: 206-723-0656


ASCA Registered Consulting Arborist®

ISA Certified Arborist

ISA Qualified Tree Risk Assessor