by William (Ned) Friedman, Director of the Arnold Arboretum and Arnold Professor of Organismic and Evolutionary Biology, Harvard University

When I contemplate what the future holds for the Arnold Arboretum—where we are just 150 years into the first half of a multi-millennial lease with the City of Boston—my frame of reference shifts from the here and now to what I think of as “tree time.”

While my research as an evolutionary biologist allows me to ponder the extraordinarily deep history of many of the species we collect, tree time represents the expected life spans of individual organisms growing in our landscape. Depending on the species, a tree planted this fall at the Arboretum may have the potential to live a hundred, two hundred, or even several hundred years—providing meaning and value to multiple generations of staff, scientists, and visitors. Ensuring that any given tree, shrub, or vine that we grow fulfils the promise of its natural history requires thoughtful and excellent stewardship that consistently addresses the challenges imposed by nature on its longevity.

All institutions make decisions with long ranging implications. But growing trees for posterity means we must always think beyond the temporal boundaries of our own lifetimes. The specter of our changing climate and the effects it will have on plants and ecosystems adds another complicating layer to this long-term planning. Our idea of tree time and how it intersects with global change comes into sharper relief when we think about the existential threat extreme drought inflicts on our collections. Water is central to supporting all the physiological functions of our plants and building resiliency against external pressures like pests and pathogens, also on the rise as our climate changes. Without adequate hydration during the growing season, tree time for every plant we grow is borrowed.

The summer of 2016 brought the worst drought to Massachusetts in recorded history—a so-called “one hundred year” event that now seems quite likely to be repeated within the decade. Look only to this past summer, when the Arboretum received just over three inches of rainfall over an eleven-week period. The 2016 drought was an urgent wake-up call for us to prioritize how we get life-sustaining water to our plants when they need it most. Within a year we had launched a major initiative to install emergency irrigation lines and water connections throughout our landscape, beginning with collections in the heart of our landscape on Bussey Hill and along Centre Street. Irrigation provided to this part of the Arboretum proved essential to the efforts of our horticulturists this summer to keep our most vulnerable plants alive.

This fall through generous donor support we have broken ground on Peters Hill for the next phase of the project, which will protect 60 acres of collections where access to water is currently the most limited in our landscape. We have also begun to plan and raise funds for the final phase of this work, which will deliver automated irrigation to an additional 60 acres of treasured collections along Hemlock Hill Road and Meadow Road, including our unrivaled and nationally-accredited collection of maples. In addition to increasing watering efficiency and absorption through controlled delivery and timing, these systems will recover significant amounts of labor and environmental impacts of watering and managing drought-induced damage across the Arboretum during the growing season.

Protecting what we grow and making the Arboretum a healthier and more sustainable environment for both plants and people is our most important responsibility to the future. In this cause we are not alone. Last month the Arboretum hosted Boston Mayor Michelle Wu and other officials for the launch of an Urban Forest Plan devoted to the growth and stewardship of our city’s tree canopy. Focused on making Boston a greener and more equitable environment for us all, the plan will only succeed through a strong commitment from the public to the trees. The trust and commitment of our community to the Arnold Arboretum and the plants that grow here has sustained us for 150 years, and we are doing everything in our power to maximize tree time for the living treasures we share with the world.