The International Society of Arboriculture: 100 Years of Service
Figure 1: A cross section of a tree provided by Dr. Alex C. Wiedenhoeft at the USDA Forest Products Laboratory in Wisconsin. Milestones noted are (1) 1924, the first National Shade Tree Conference is held; (2) 1942, the first chapters of the National Shade Tree Conference (NSTC) are formed; (3) 1946, creation of the Memorial Research Fund; (4) 1961, the first International Shade Tree Conference; (5) 1975, the Journal of Arboriculture is first published; (6) 1976, the first International Tree Climbing Jamboree is held; (7) 1992, ISA’s Arborist Certification Program is launched; (8) 1992, ISA’s newsletter is relaunched as Arborist News; (9) 1995, ISA’s website is established; (10) 1998, the first ISA Conference is held outside of North America; (11) 2013, the Tree Risk Assessment Qualification is created; and (12) 2024, ISA celebrates its 100-year anniversary.
This article was the first in a year-long series celebrating the International Society of Arboriculture’s (ISA’s) 100th anniversary. It ran in Arborist News, ISA’s member newsletter, in August 2023, and is reprinted here with permission to celebrate ISA’s anniversary. Each article in the series highlighted certain aspects of ISA’s history. This article presents an overview of the organization’s growth through the decades.
“As I was recently looking through boxes of historical documents in preparation for ISA’s upcoming 100-year anniversary, I found a fresh outlook on the critical role that ISA has played in promoting the professional practice of arboriculture throughout the past century. It is vital that we preserve this heritage and honor the legacy of those who had the foresight to bring our organization to fruition. I can only imagine how those first participants of our very first meeting would react if they knew 100 years later their initiative would still be going strong with more than 26,000 members in 70 countries.
– Caitlyn Pollihan, ISA CEO and Executive Director
The International Society of Arboriculture and the profession of arboriculture share a rich history. Although arboriculture can trace its roots back thousands of years, its development as a profession parallels the emergence and growth of ISA. (Figure 1)
Arboriculture as a profession
By the late 1800s, plant care had become an established and rapidly growing profession. During that same era, expanding industrialization and urbanization were adding new stresses to trees, and the detrimental effects were becoming apparent. Unfortunately, scientific understanding of plant dysfunction and reliable information about plant care were scarce. (Figure 2)
By the start of the 20th century, some tree companies had begun their own research efforts, and some lectured to local audiences. In 1901, John Davey, founder of the Davey Tree Expert Company, wrote “The Tree Doctor.” In the book’s introduction, Mr. Davey observed:
The time has come when tree planting and tree culture must be studied in connection with the physiology of plant life. If this is not done, a calamity will befall the inhabitants of these fruitful regions to an extent that no human mind can conceive.
Other plant-care practitioners across North America and Europe were expressing similar sentiments.
It was not until 1924, however, that members of the Connecticut Tree Protective Association convened a meeting that would plant a seed of an institution that would ultimately revolutionize the tree care industry. It was this gathering that was to become the first of 100 annual conferences of the organization that has evolved into today’s International Society of Arboriculture (ISA). Indeed, the history of modern arboriculture largely coincides with the history of ISA.
Figure 2: Before the advent of small, one-man chain saws and aerial lifts, all tree work was performed manually. Fortunately, the climbing gear and saws have evolved to make tree climbing safer and more efficient. Unless otherwise noted, all photos courtesy of ISA.
1920s
The organization began as a marriage of convenience between progressive commercial arborists and scientists whose research concerned trees. Although tree care had been practiced by commercial companies and individuals for years, the industry was largely unregulated and uninformed. As for the scientists, their knowledge of amenity trees and tree care was somewhat limited. There were many demanding questions in horticulture, forestry, entomology and pathology concerning trees – issues that required research for answers.
Birth of the organization
The Shade Tree Conference (STC) first met in 1924 in Stamford, Connecticut. W.E. Britton, along with Francis A. Bartlett, president of The F.A. Bartlett Tree Expert Company in Stamford, were the two principal figures in organizing the conference. At the invitation of Bartlett, some of the meetings were held on his experimental farm north of Stamford. The conference opened with about 36 participants from seven states and Washington, D.C. (Figure 3)
Bartlett established a conference format combining paper presentations with field demonstrations and trials. Presentations were made on a variety of topics, including gypsy-moth control, tree surgery and wound healing, and were limited to five minutes each. A significant aspect of this conference is that it united the Davey Tree Expert Company, The F.A. Bartlett Tree Expert Company and several smaller commercial firms in the pursuit of a common goal.
At the fourth conference, held in Washington, D.C., the most significant event was the endorsement of the articles of organization recommended by a committee appointed at the 1926 conference. This action created the National Shade Tree Conference (NSTC), marking the formal beginning of a new era in the history of arboriculture. An interesting footnote to the early structure is that commercial arborists were ineligible to hold office but were solely responsible for financing the conferences.
Figure 3: Program of the first Shade Tree Conference in 1924, which would later become the National Shade Tree Conference (NSTC)
1930s
In the early years, the people who practiced arboriculture were typically called tree experts or tree surgeons. The term “tree surgeon” actually reflected some of the prominent practices of the time: cavity cleaning and filling, bark tracing and pruning. The first use of the word “arboriculture” in the proceedings of the NSTC was by Charles Irish in 1932 in his paper, “Highlights in the Early History of Arboriculture.” Irish noted that the term had been used in England for more than 300 years. The use of arborist and arboriculture became popular in America in the 1930s to differentiate tree care from forestry.
The Great Depression years in the 1930s saw unemployment reach unprecedented levels. During the same period, utility wires were being strung all across North America. A new niche in arboriculture was born, and line clearance would become an important sector in the industry.
Lewis C. (Chad) Chadwick from The Ohio State University became the first executive secretary in 1937, managing the organization from his home. More than any other individual, Chadwick influenced the growth and direction of the Conference over the following three decades.
Figure 4: NSTC Banquet – Belle Isle, Michigan, 1940.
1940s
The NSTC was growing and spreading at a rate the founders never expected. There was a need to form regional chapters to improve information exchange. In 1941, the NSTC defined six geographical regions within the United States. In 1942, the first three chapters were created: the Ohio, the Western and the Southern Chapters, the latter two having begun and existed as independent conferences. Soon, other regions followed suit by creating chapters. (Figure 4)
World War II had a tremendous impact on the arboriculture industry. The labor force was decimated almost overnight as young men left for military service. Supplies and tools were scarce, and gasoline was rationed. Tree companies joined the war effort by volunteering their services for camouflage duties and by registering their equipment for possible service in fire brigades or transport. The leaders of the NSTC and the National Arborist Association (NAA, now TCIA), formed in 1938, advised arborists to lay in adequate supplies of fertilizers, fungicides and insecticides.
The war provided one bright light for tree care companies – line clearance was declared an imperative for national defense. Power for war industries was essential; telegraph and telephone communication was vital, as was railroad and vehicular transportation for rapid supply and transport. More than two-thirds of the remaining personnel in arboriculture would be performing line-clearing work before the war ended. This had great significance on the survival of many tree companies and influenced pruning practices for several decades to come.
In 1946, the NSTC marked two significant events in its history: the adoption of a Code of Ethics for arborists and the creation of a fund for research. The Code of Ethics was seen as an important step toward advancing arboriculture as a respected profession. The Memorial Research Fund was formally established on 12 December 1946, with $2,000 transferred from the general fund of the NSTC. This research fund represented a new opportunity and an obligation for arborists to sponsor at least part of the research from which they were the principal beneficiaries.
Figure 5: Opening ceremony, San Francisco, 1962, a year after the meeting became the International Shade Tree Conference.
1950s
In 1957, “Shade Tree Evaluation” was published under the direction of Norman Armstrong. For the first time, the Conference was able to provide a sound basis for evaluating trees. This publication is now in its tenth edition, and in 1992 the title was changed to “Guide for Plant Appraisal.” The Council of Tree and Landscape Appraisers (CTLA) authored later revisions.
Figure 6: The aerial-rescue event at the first ISA Jamboree in 1976.
1960s
In 1960, Canadian members petitioned the NSTC to change its name from National to International. Accordingly, the organization became the International Shade Tree Conference (ISTC) in 1961. (Figure 5)
In 1963, the Conference created awards to recognize the service of its members. The Author’s Citation was granted to authors for sustained excellence in the publication of timely information pertaining to the field of arboriculture. The Award of Merit was designed to recognize meritorious service in advancing the principles, ideals and practices of arboriculture, and is the highest award made by the Society (ISA).
By 1964, it had become apparent that new action had to be initiated for the future of the ISTC, because the heavy burden of work and responsibility for the ISTC could no longer be continued on a part-time basis. In recognition of his contributions, the Conference changed Lewis Chadwick’s official status in 1966 from secretary-treasurer to executive director. Chadwick retired as executive director in 1969 to an emeritus status. The Executive Committee then appointed Dr. Eugene B. Himelick as an unpaid executive director and Ervin C. (Cal) Bundy as full-time executive secretary, and the official office was moved from Chadwick’s home in Columbus, Ohio, to Urbana, Illinois.
Professional affiliations
The origin and development of “special-interest groups,” such as utility, commercial and municipal arborists, began with discussion sessions at conferences in the 1950s and 1960s. Beginning in 1969, these groups were granted a recognized status as special-interest organizations within the Conference. A new article of the Constitution in 1969 provided for “associated special-interest groups” within the Conference. The term “special-interest group” would later be changed to “professional affiliation.”
1970s
The 50th anniversary of the Conference in 1974 was marked by the creation of a new professional journal. Dr. Dan Neely, ISTC editor since 1970, was appointed editor of the Journal of Arboriculture in January 1975, and the original Arborist’s News publication was discontinued.
International Society of Arboriculture
The organization that began as a conference in 1924 became the International Society of Arboriculture on January 1, 1976. This name change, along with the creation of the new Journal of Arboriculture, gave the Society a new professional status. A new constitution and bylaws for the newly created ISA also were approved.
Tree-climbing competition
Also in 1976, ISA executive director Eugene Himelick initiated the first International Tree Climbing Jamboree at the annual conference held in St. Louis, Missouri. The goal of the event was to demonstrate skills; however, safety in tree work was an essential component of the competition. The first World Champion Tree Climber (in 1976) was Tom Gosnell of Santa Barbara, California. (Figure 6)
A full-time executive-director position was created in 1979, and the position of executive secretary was eliminated. Cal Bundy, the executive secretary, was appointed as the first full-time executive director. The 1970s saw rapid growth of the Society, with membership topping 3,000 professionals by the end of the decade.
1980s
By vote of its members, the ISA Board of Governors was terminated as the governing body of the Society in 1985. By the same action, its responsibilities as organizational and corporate authority of ISA were transferred to the ISA Board of Directors, and the duty of the Board of Governors to elect board members was transferred to affiliated chapters of ISA.
William P. Kruidenier succeeded Cal Bundy as executive director on July 1, 1987, in the midst of an era of vision and expansion for ISA. Growth of the organization was creating a need for more office space, and, in 1988, ISA’s headquarters offices were moved from the lower-level office of a downtown Urbana shopping mall to an historic Greek Revival cottage in Urbana’s Leal Park. The wood-frame cottage, built about 1856, was located in a two-acre park and surrounded, appropriately, by 200-year-old trees.
Figure 7: The original ISA Certified Arborist logo in 1992.
1990s
Arborist Certification
In 1992, ISA launched an unprecedented program of Arborist Certification on an international scale. The goal was to raise the level of professionalism in arboriculture by educating the providers of tree care services. The program tested and certified an individual’s knowledge in the field of arboriculture and attested to a generally accepted level of knowledge.
The ISA Arborist Certification program was immediately successful on several levels. Certification increased the level of tree care knowledge among practitioners and improved professionalism within the tree care industry. The program was also successful for ISA, increasing membership dramatically and creating demand for educational programming and materials. (Figure 7)
Education and training
In 1992, the Journal of Arboriculture became bimonthly and there was a rebirth of Arborist News (note the change in spelling) – a greatly expanded and improved bimonthly magazine. Arborist News added several new popular features, including continuing education unit (CEU) articles, which offered credits for recertification. (Figure 8)
With the increased focus on publication development through the 1990s, ISA established “families” of publications targeted to meet the needs of various sectors of its membership. While many publications serve multidisciplinary needs, the ISA arboricultural families included commercial, utility, municipal and research/education. The Society also produced a variety of youth-education and public-relations materials available in book, brochure or press-release formats.
Internationalization
In addition to the exponential growth in membership, the 1990s began a period of international expansion of ISA, with 12 chapters forming outside North America. Eight chapters were added in Europe, as well as one each in Brazil, Mexico, Australia and New Zealand. In 1998, the Society held its annual conference outside the North American continent for the first time. More than 1,200 delegates from 36 countries attended this conference in Birmingham, England.
ISA on the internet
In 1995, the Executive Committee approved contracting with the University of Illinois to establish an ISA home page on the internet. The site was established in 1995 with a focus on plant-health-care information, a “chat page” for tree workers and general information on ISA and its various programs. There were more than 1,000 visitors to the page in the early months, and use grew to more than 140,000 visits per month by 1999.
2000s
With the growing interest in certification and the thirst for more professional education, driven largely by the need for certification CEUs, ISA’s growth and world influence grew dramatically in the 2000s. By the middle of the decade, membership had passed 20,000, and credential holders numbered more than 25,000. (Figure 9)
Technology brought a change in education delivery with training videos and interactive, computer-based courses, as well as other e-learning opportunities, including podcasts, webinars and online CEU quizzes. Computer-based testing also was launched for Certified Arborists and Board Certified Master Arborists (BCMAs).
Paul Harter became the ISA Executive Director in 2000, leveraging an extensive business background to restructure ISA finances and policies and leading ISA through some cash-flow difficulties. He was succeeded a few years later by Jim Skiera, who continued internal-process improvements and increased the focus on international development.
Figure 8: Front cover of the first issue of Arborist News, printed in February 1992.
2010s
A major change in 2010 came about when ISA converted its governance structure to a 15-person Board, replacing the oversized Board that consisted of representatives of every chapter, and creating the Council of Representatives.
ISA and its many chapters enjoyed a growing demand for conferences and other in-person education opportunities. The need was particularly strong in Asia, where ISA credentials had become increasingly important. ISA partnered with its various affiliations to organize workshops and training sessions. In 2021, ISA held its international conference in Parramatta, New South Wales, Australia; it was the second time outside North America and the first in the Asia-Pacific region. ISA also increased support for regional tree-climbing competitions.
Online resources became an integral part of continuing education as well as international expansion. ISA restructured its multilingual online glossary of arboricultural terms and translation tool, and it funded the development of translation glossaries in many languages. This would pave the way for translation of many of ISA’s educational and public-relations resources into various languages around the world. Social media, including Facebook, Twitter and LinkedIn, became an important part of ISA communication and networking.
Perhaps the biggest highlight of the decade was the launch of the Tree Risk Assessment Qualification (TRAQ), which grew rapidly to become among ISA’s most recognized credentials.
The decade ended with a changing of the guard as Executive Director Jim Skiera retired and Caitlyn Pollihan took over. The headquarters office pulled up roots and transplanted to Atlanta, Georgia, marking the start of a new era. (Figure 10)
Figure 9: A selection of ISA’s current educational offerings, from study guides to Best Management Practices.
2020s
The most recent decade got off to a difficult start with a worldwide pandemic, global shutdowns and a roller-coaster economy. Fortunately, ISA’s strong financial reserves and careful fiscal leadership helped ISA survive those years and resume growth in its membership and programming.
What began as a tree care conference in 1924 has continued to grow from those roots through the decades. Through the years, the original concept of research-based tree care has expanded, and the more questions that were answered, the more questions were uncovered. The profession became increasingly diverse, and ISA broadened its scope to meet its varying needs. It united the various facets – the workers, researchers, suppliers and consultants – in a common mission of caring for trees in the best way we know how.
The Shade Tree Conference has always been more than an educational seminar. It brings people together from all over the world to share new ideas, techniques, equipment and problems in need of solutions. It fosters a synergy, combining the energy of the workers in the trees with the knowledge of the scientists in the laboratories. It is a celebration of people who share the same interests and a reunion of those who solved yesterday’s problems. The ISA conference has built lasting friendships and lifelong memories.
ISA has a rich history that includes a metamorphosis from its fledgling beginnings to the grand organization that it is today. Throughout it all, one thing has remained the same: the dedication of the professionals who create, organize and administer the many programs from which we all benefit. As ISA enters its second century, the officers, Board of Directors, committee chairs, staff and many volunteers share a common vision for the future of the organization: to foster research and education for the care and preservation of trees.
As the saying goes, “Mighty oaks from little acorns grow.”
This article is based largely on ISA’s publication, “Memory Lane,” by Richard Campana and Sharon Lilly.
Figure 10: The new ISA offices in downtown Atlanta, Georgia.
Sharon Lilly worked as a commercial arborist for 25 years, mostly in the field. In 1997, she became the first woman president of ISA. She helped in the development of arborist certification and is a former chair of the ISA Certification Board. More recently, she helped develop the TRAQ credential. She is the author of several books, including the “ISA Arborist Certification Study Guide,” “The Tree Climbers’ Guide,” “The Tree Worker’s Manual” and “Managing Golf Course Trees,” as well as countless articles, manuals, workbooks and other publications and study materials. She continues to write and conduct seminars on many aspects of arboriculture.
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