This year, 2025, marks 30 years since “ANSI A300 Part 1, Pruning” was published. Where would the industry be without this guidance?

Photo 1: Topping of trees was common practice in utility, municipal and residential settings. Photo courtesy of the author.

Prior to 1995, there was wide variation in what was considered good or bad tree care. Research was published, but often not widely disseminated. Questionable techniques were handed down from previous generations, based mostly on tradition. Some of us remember filling cavities with concrete, pruning with flush cuts and removing far too many trees without first analyzing the actual risk posed. Topping and lion-tailing of trees were common practices. Utilities routinely “rounded over” trees under power lines (Photo 1). There are still subpar practices, but as an industry we have come far – and ANSI A300 has led the way.

In 1991, a handful of forward-thinking industry leaders looked to standardize science-based tree care practices across the U.S. “ANSI A300 Part 1, Pruning” was published in 1995. Over the next 15 years, nine more standards were added, each defining practices for an important aspect of arboriculture. And finally, in 2023, all 10 standards were combined into a single volume. After 30 years, we can look back at what we’ve accomplished and consider where we go next.

History: Use of ANSI
The American National Standards Institute (ANSI) is a non-profit organization that coordinates the development of all kinds of American industry standards. To develop and maintain a standard, ANSI requires an organization (known as the secretariat) to organize the committee and house the documents.

The International Society of Arboriculture (ISA) has been Secretariat for ANSI Z133.1 (Safety) since 1971. To develop ANSI A300, the National Arborist Association (NAA, now TCIA) assigned staffer Brian Barnard (now with Grand Arbor Supply) to be the Secretary for the proposed new American National Standard. “When I approached ANSI with this idea, they wondered why arborists needed another standard,” notes Barnard. “I had to explain that this was about the practice of arboriculture, beyond safe operations.”

But why involve a second organization, since ISA was already handling Z133.1? According to Barnard, “The NAA represented arborists from around the country, and with ISA managing Z133.1, it was natural to have NAA handle A300.”

Photo 2: A Spanish translation of ANSI A300 is now available. Image courtesy of TCIA.

The initial Accredited Standards Committee (ASC) A300 consisted of 16 members (plus alternates, see Figure 1) representing a range of interests and expertise. “Bob [NAA Executive Director Robert Felix] approached me and asked me if I would chair the committee,” recalls then-NAA board member Tim Johnson. “He knew I didn’t have an agenda that would bias the work of the group. We had the first meeting in the basement of the USDA Forest Service offices in Washington, D.C.”

“It was a privilege to work with these very talented arborists from around the country,” comments Barnard. “Even though they represented diverse interests, it was not contentious. Everyone recognized the need for a uniform standard for all arborists. Everyone was anti-topping. Dr. Shigo’s research and methods were discussed at length, including for line clearance.”

The ANSI process ensured that all interested parties would have a voice, that relevant research would be included and that the resulting standard would be credible. These rules, plus logistical considerations, slowed the process of developing the first version of ANSI A300. According to Barnard, “This had never been done before. Terminology needed to be uniform across the country. And communication was more difficult back then – no internet, no email. Routine correspondence and public comments were all done by snail mail. There were no conference calls; everyone flew to Washington twice a year.”

Why start with pruning?
The current ANSI A300 “standard” has 10 “clauses” covering common arboricultural practices. (Each clause is made up of many individual standards, or standard practices.)

“The initial focus was pruning,” notes Barnard. “Pruning was something every company did. Everyone on the committee was anti-topping, including the utility arborists.” The intention was to eventually expand the scope, but it was clear a focus on pruning first would have the greatest impact.

Finding consensus
One of ANSI’s basic principles is operating by consensus. Though committee members respected one another, they did not necessarily see eye to eye on every issue. This is not surprising, considering the diverse interests – utility, municipal, commercial, government – sitting around the table. “There were occasional divisions” notes Johnson. “There was friction between the academics, who tended to be purists, and the field people, who were more practical. But eventually, everyone understood that the standard had to accommodate different pruning objectives.”

Bob Rouse, TCIA senior vice president of industry expertise, has been the ASC A300 Secretary since 1997 and has watched the group grapple with the concept of consensus. “ANSI does not require unanimity, but it does require consideration of all views and any objections,” says Rouse. “If committee members can accept the results, it qualifies as consensus and the process can move forward.”

Dr. E. Thomas Smiley, a technical expert and Bartlett’s alternate representative since 1996, commented about consensus. “It’s a basic ANSI requirement that has worked well for us because we are science-based, and committee members respect this.” Sometimes disagreements led to drawn-out discussions that came down to the interpretation of a single word or phrase. “Fewer words are less ambiguous,” says Smiley. “We try to cover just the basic principles in the standard and leave the explanations and nuances for the annexes and best-practice guides.”

A300 applies across the United States (nursery and forestry operations were and still are exempt). That means that arborists working on a Sitka spruce in Juneau, a dogwood in Georgia, a valley oak in California or a ficus in South Florida are all subject to the same standard. “We accommodated regional needs by careful use of the terms ‘should’ and ‘shall,’” says Johnson. “If it applied everywhere, all the time, it’s ‘shall.’ Use of ‘should’ allowed some flexibility. But when writing specs for professional work, there can be no ambiguity.”

Photo 3: Posing during a spring 2025 A300 committee meeting in Phoenix, Arizona, are, from left, Sam Hill, current chair of ASC A300; Bob Rouse, A300 Secretary; Geoff Kempter, committee member; and Tim Johnson, original A300 committee chair. Photo courtesy of the author.

Initial reception
From the beginning, there was pushback. The Utility Arborist Association, fearing restrictions on utility pruning operations, insisted on a separate section to highlight their interests and exempt them from certain requirements. Corporate legal departments were wary of liability. Arborists are an independent bunch, and many regarded the standard and its requirements as an imposition.

But by far the biggest problem was getting arborists to recognize and use the standards. “There has always been a need for education,” notes Rouse. “We promoted them through the ASC A300 member organizations and annually at TCI EXPO. We also put on regional workshops all over the country, wherever the committee met.”

Additional parts
The pruning standard was a heavy lift, but committee members now knew the process and could turn their attention to other aspects of tree care. Over the next 15 years, nine more parts would be added, and revisions of existing standards were completed as required. In 2008, with the second revision of Pruning, the focus of A300 was changed from “maintenance” to “management.” “We wanted to focus on management to meet objectives, to emphasize the benefits of our service,” notes Johnson.

Going back to the 1930s, the National Park Service (NPS) had standardized practices for pruning, fertilization, cabling and bracing and lightning protection. Starting in the 1940s, NAA created standards based on the NPS documents. By 2002, these were developed into the first four parts of ANSI A300.

“Part 5, Management During Site Planning, Site Development, and Construction” (published in 2005), was a significant shift. Rather than defining practices for working directly on trees, this was for working around trees on a development site. “We saw another need, and this was the next logical step” says Johnson. “Part 6, Transplanting,” also published in 2005, proved challenging, as methods varied significantly across the country. However, there was nearly universal agreement that planting practices needed to be standardized, and that everywhere, plant materials were consistently being planted too deeply.

In 2003, a blackout initiated by a tree on an electric-transmission right-of-way affected more than 50 million people in eastern North America. At that time, there was no national standard for vegetation management. Following this incident, regulatory scrutiny increased, and the Utility Arborist Association requested that ASC A300 develop a standard for integrated vegetation management (IVM). The committee agreed, and “Part 7, Integrated Vegetation Management (IVM)” was published in 2006.

“Part 8, Root Management” (published in 2013) focused on trenching near trees, root pruning, girdling roots and other below-ground concerns. “Part 9, Tree Risk Assessment” followed in 2011, and was used to help develop ISA’s Tree Risk Assessment Qualification. The last standard to be developed was “Part 10, Plant Health Care,” in 2012. Part 10 emphasized an integrated approach to managing pests on woody plants.

Photo 4: Members of the current A300 committee at their fall 2025 meeting in New Orleans, Louisiana. Each is holding a copy of the new ANSI A300 standard. TCIA staff photo. Meting in New Orleans, LA.

Impact on arboriculture
As more parts were added, ANSI A300 came into wider use. Most utilities and municipalities altered their work specifications to comply with A300. ISA ensured that their series of Best Management Practices guides were in alignment. The principles defined in A300, along with standards from other countries, became drivers of industry certification and accreditation programs. In this way, A300 has helped to increase the level of professionalism across the tree care industry. “The impact of the standard has been transformative,” comments committee member Randall H. Miller. “It has advanced professionalism on par with arborist certification, TCIA Accreditation and other credentialing programs.”

The standards are written to allow the flexibility needed to meet changing conditions. Every tree is different, every client is unique and every arborist has an opinion. Use of the standards to write work specifications allows arborists to provide better and more consistent service for clients. “As a business owner, I have always tried to stay current with both A300 and the Z,” notes current ASC A300 chair Sam Hill. “We want arborists to use the language in the standards to accomplish the job and their client’s objectives. And – when necessary – to be able to defend what they’ve done.”

A300 is not written to be law, but courts turn to industry standards to determine liability when there are problems. Standards can serve as the basis for statutes and codes; however it is important to ensure that these codes are updated as standards are revised. (The A300 standards are updated/revised every five years, as required by ANSI.) Arborists can protect themselves from liability by understanding the standards and applying them on the job. “Many companies use the standards in their marketing, but they don’t always comply. When things go wrong, they get hammered,” says Johnson, who frequently serves as an expert witness in legal cases.

To get the word out, TCIA continues to promote the standards through online courses, TCIA’s webpage, articles in TCI Magazine, regional workshops and annually at TCI EXPO. Using the standards as a basis for writing specifications is the primary focus of these outreach efforts. In addition to taking A300 back to their own organizations, ASC A300 members are encouraged to publicize the standards by speaking at conferences and promoting them to green-industry groups in their areas.

Spanish translation
This year, ANSI A300 was published in Spanish. (Photo 2). The work was facilitated by ASC A300 Committee member Demian Gomez. Originally from Uruguay, Gomez obtained is Ph.D. in Forest Resources and Conservation from the University of Florida and is now the regional forest health coordinator with Texas A&M Forest Service. Gomez points out that with so many industry workers with Spanish as their first language in the U.S., it is important for them to have access to this valuable information. “Much time and effort went into this translation,” says Gomez. “Many volunteers worked to establish common terminology that served as the starting point to translate the standards.” With the standard now available in Spanish, it will be possible for Latin American countries to develop their own standards and guidelines for proper tree care. (For more on the A300 course Spanish Translation, see sidebar, page 51.)

Looking forward
Thirty years after the initial publishing of “ANSI A300 Part 1, Pruning,” the work of ASC A300 continues. (Photos 3 & 4) Following the consolidation of the standard into one volume in 2023, the committee is working toward revising the entire standard on schedule by 2028.

A nearly universal feeling among committee members is the respect they have for one another. Dr. Ricard Hauer has been on ASC A300 since 2013, and has represented ISA and Wright Service Corporation. “I have learned so much,” comments Hauer. “The collective expertise, working with these great minds from across the country, it’s amazing, and a real privilege.”

After 30 years, ANSI A300 is recognized as a definitive force for improvement in arboriculture. It is important to remember that ASC A300 represents the entire industry and depends on constituents to comment on and improve the standard. “We have accomplished quite a bit, but there is always more to do,” notes original chair Tim Johnson. “It’s very much worth moving forward – we still plant things too deep!”

Geoff Kempter was the Asplundh representative to ASC A300 from 1996-2024, and currently serves as the alternate representative for TCIA.