Phenology–the study of the seasonal rhythm of plants and animals–is a science with deep roots in cultural practices throughout human history. Modern research examines trends in phenological data to help us understand our changing climate, but observation of the timing of biological events has long served social and economic purposes outside the realm of scientific inquiry. From records of cherry blossom festivals in Japan to wine grape harvest dates from Burgundy, preserved phenological data sets (often hidden within historical documents) offer us both a glimpse into our past and a foundation for studying our future. Today, phenology plays an important role in research and outreach here at the Arnold Arboretum. But did you know that a hundred-year-old phenological data sets resides here at the Arboretum, tucked among the 25,000 volumes of the Arboretum’s Horticultural Library?
On May 2nd of 1911, the publication that would later become Arnoldia, the Arboretum’s quarterly magazine, began its life as The Bulletin of Popular Information. A humble pamphlet devoid of images, The Bulletin was the creation of the Arboretum’s first director, Charles Sprague Sargent, a distinguished American botanist and prolific writer who served the institution for over 50 years. Through his weekly publication, running only during the growing season, Sargent informed the Arboretum’s visitors of botanical happenings on the grounds, so as to instruct them on when best to visit the collections. Conveying the timing of these events was of utmost importance to the director, as we read in the wonderfully serious preface to bulletin no. 1:
Persons interested in plants often complain that they do not know when the trees and shrubs in the Arboretum bloom and therefore miss flowers which they want to see. To meet this difficulty it is proposed to issue from time to time from the Arboretum bulletins of popular information in which attention will be called to the flowering of important plants and other matters connected with them. During the spring and autumn these bulletins will probably be issued every Saturday and from time to time during the remainder of the year when the necessity for them exists; and in them notice will be given of what will be best worth seeing during the following week.
Despite its modest format, The Bulletin is a treasure among the Arboretum’s archives. Through his writings, Sargent invited readers on a personal tour, advertising in vivid detail the many wonders to be found on the Arboretum’s grounds. Until his death in 1927, Sargent dutifully reported on the status of the collections, recounted weather conditions, discussed horticultural matters, and waxed philosophical in the pages of The Bulletin. The earliest days of the publication offer both an intimate look through the eyes of the Arboretum’s first director and a detailed phenological record of the plants that captivated him. In time, The Bulletin would become Arnoldia, the Arboretum’s quarterly magazine covering a variety of scholarly topics with many guest contributors (and a much catchier title).
To celebrate the anniversary of The Bulletin, I decided to take a walk with Sargent through the Arboretum’s collections on May 2nd, 2017–exactly 106 years after the first publication of this historical document. Curious to compare observations, I visited the species mentioned by Sargent in bulletin no. 1. Winding my way through the grounds, I photographed these plants and made note of their phenological status.
On the whole, I found that most (nearly all) of the species mentioned by Sargent as flowering on May 2nd, 1911, had flowered weeks beforehand in 2017. In referencing images I’d taken earlier in spring, I saw that the most of the magnolias near the Hunnewell building, including many described by Sargent, had reached peak flowering around April 18th. Additionally, the cherries referenced by Sargent, notably Prunus subhirtella and Prunus pendula, had passed, with Prunus sargentii having already gone to fruit! Sargent mentions only one Rhododendron species blooming by May 2nd (Rhododendron mucronulatum), but I observed a variety of red, pink and magenta blooms on azaleas and rhododendrons throughout the grounds. I found the most striking differences among the flowering times of Forsythia intermedia which had long since passed by May 2nd (see images of Bussey Hill, below), and Amalanchier canadensis, which began flowering by April 15th of this year, but had not begun flowering by the time of The Bulletin‘s first publication on May 2nd, 1911.
While this exercise can hardly be considered a rigorous scientific study, these simple observations still show us clear phenological differences between flowering times in 1911 and 2017. Among the plants mentioned by Sargent, nearly all, with the exception of Ribes (Currants and Gooseberries) reached peak flowering in mid to late April this year, weeks ahead of Sargent’s observations in 1911. If we wanted to learn more about the intervening years, between Sargent’s time and ours, we could expand this study to include additional observations from The Bulletin, specimens from herbaria, photographs from the visual archives, and other data from the many phenological records in the Arboretum’s collections.
Today, a century after the initial publication of The Bulletin, Sargent’s picturesque vision of his Arboretum and his careful observations of its living collection are as captivating as ever. This season, take a walk with the Arboretum’s first director, and learn about the many phenological marvels that connect us to this institution’s storied past.
If you are interested in learning more about phenology, botany, or ecology, join the Arnold Aboretum Tree Spotters, a group of citizen scientists who collect data from 11 species throughout the Arboretum to assist studies focused on plant responses to climate change. Read more about Tree Spotters in Silva [pdf].