What is the Arnold Arboretum? This question has been at the center of my thinking for over a decade, especially now, as I enter the twelfth year of my directorship and the Arnold enters its 150th year. Of course, nothing should ever be static when it comes to the life of an institution. Founding nineteenth-century ideals need updating in the twenty-first century. Still, for all that has changed over the last century and a half, the core values of the Arnold Arboretum strike me as eternal.

The Arnold Arboretum has and will always serve as a crossroads for biodiversity and human diversity. Its founding was a testament to the enduring values of democratic spaces (free and open to all) and the belief that such places should uplift all who enter. The Arnold is also, from the outset, an institution defined by its association with Harvard University. Scholarship, born of a love of biodiversity and a desire to unlock its secrets, is central. An ethos of conservation and respect for the environment goes back to the founders and early leaders. The meanings of such an intermingling of sentient and nonsentient organisms (respectively, people and trees) can never be fully unpacked, even in a lifetime of pondering. Yet I will briefly reflect on my thinking.

Let’s begin with my definition of an arboretum: a collection of woody plants with provenance in a designed landscape. Here, provenance and designed landscape are essential characteristics that help us appreciate the varied and dynamic relationships that occur between people, uniquely identified botanical organisms, and arboretum landscapes. The concept of provenance is typically associated with museum objects (think artworks), and at the Arnold Arboretum, every organism has a documented and acknowledged history. Take, for example, a single specimen of the sand pear (Pyrus pyrifolia, accession 7272*C) that has grown on the top of Bussey Hill for over a century.

We know that Ernest Henry Wilson and his collecting team encountered the parent of this sand pear growing west of Yichang, China, in the late summer of 1907. They collected fruit, removed its pulp (perhaps by eating it?), and separated, dried, and packed the seeds. The packet then passed as cargo down the Yangtze River to Shanghai, made its way by steamer to the west coast of North America, and took the transcontinental trains to Boston. On April 15, 1908, an Arboretum propagator formally accessioned the seeds. A few years later, a spot for a young sapling was chosen, and a hole was dug. This wonderful organism has lived in this location ever since, battling plant diseases and delighting visitors with its extraordinary clouds of white flowers every spring. This specimen is not any sand pear. It is an individual with its own life history and standing, not interchangeable with any other sand pear on Earth, just as no two human beings are interchangeable. Such provenance—granular and unique—distinguishes almost all the Arboretum’s roughly sixteen thousand accessioned woody plants.

The Arnold Arboretum is literally interwoven into the healthcare system of Boston.

A designed landscape is also central to my definition of an arboretum, and the Arnold Arboretum is fortunate to have been designed by a visionary—Frederick Law Olmsted. His intentional design is reflected in every inch of the grounds, like the majestic reveal as you round the bend on Hemlock Hill Road and unexpectedly view the dramatic mixture of spruces and firs, with their blues and seemingly endless hues of green. The intentionality can be felt as you stand under the cathedral-like oak collection or take in a seemingly endless run of mountain laurels in flower in the spring. This landscape was designed to affect us and, indeed, to lift our spirits every day.

The impact of these experiences is profound. Olmsted spoke of the power of institutions like the Arnold Arboretum “to make life in the city healthier and happier.” But, surely Olmsted, despite his public health credentials (as general secretary of the US Sanitary Commission during the Civil War), would never have dreamed of the slew of well-documented health benefits of beautiful urban green spaces such as the Arnold Arboretum. Those who regularly walk these grounds may experience (on average) lower blood pressure, improved postoperative recovery, improved birth outcomes, improved outcomes associated with congestive heart failure, improved child development, reduced mortality, reduced stress, reduced symptoms of attention deficit hyperactivity disorder, reduced depression, and greater life satisfaction—the list goes on. The Arnold Arboretum is literally interwoven into the healthcare system of Boston.

On a global scale, the research and conservation functions of the Arnold Arboretum have never been more critical. Fully three-quarters of the research now being conducted in the living collections is centered on understanding and combating human-induced global change, including climate change. How will trees and forested ecosystems function going forward, as climactic extremes mount by the year and invasive pests and pathogens circle the globe? The Arnold’s “working” collection of woody plants is on the job providing essential insights into the coming biological Armageddon. Our plant expeditions throughout the temperate regions of the Northern Hemisphere emphasize the collection of germplasm from species and populations that are threatened with extinction. Ex situ conservation, the maintenance of living collections of endangered plants in botanical gardens and arboreta, has never been more critical to the Arnold’s mission and to Earth’s botanical biodiversity.

I could go on but will finish by reflecting on the last two years of the Arnold Arboretum’s existence. Through a raging and lethal pandemic, a reckoning over systemic racial injustice, an insurrection and serious challenge to American democracy, and the evermore obvious extreme fires, floods, droughts, heat waves, and other threats to the world’s four-billion-year evolution, the Arnold Arboretum did not close for a minute.

The Arnold Arboretum is not a mere amenity or simply a pleasure ground. It is an essential part of the public healthcare system, a place where the diverse population of Boston mixes, a bulwark for democracy, a leader in fighting global change and extinction, and a place where the next generation of ecologists, evolutionary biologists, and conservationists will launch their careers. And standing behind all of this are the magnificent plants with provenance in an Olmsted-designed landscape. What could possibly be more beautiful and meaningful as the Arnold Arboretum launches into its next century and a half?

William (Ned) Friedman is the eight director of the Arnold Arboretum and the Arnold Professor of Organismic and Evolutionary Biology at Harvard University.

From “free” to “friend”…

Established in 1911 as the Bulletin of Popular Information, Arnoldia has long been a definitive forum for conversations about temperate woody plants and their landscapes. In 2022, we rolled out a new vision for the magazine as a vigorous forum for tales of plant exploration, behind-the-scenes glimpses of botanical research, and deep dives into the history of gardens, landscapes, and science. The new Arnoldia includes poetry, visual art, and literary essays, following the human imagination wherever it entangles with trees.

It takes resources to gather and nurture these new voices, and we depend on the support of our member-subscribers to make it possible. But membership means more: by becoming a member of the Arnold Arboretum, you help to keep our collection vibrant and our research and educational mission active. Through the pages of Arnoldia, you can take part in the life of this free-to-all landscape whether you live next door or an ocean away.

For more tree-entangled art, science, and writing, subscribe to Arnoldia by becoming a member of the Arnold Arboretum.