When lilacs last in the dooryard bloom’d,
And the great star early droop’d in the western sky in the night,
I mourn’d, and yet shall mourn with ever-returning spring.
Ever-returning spring, trinity sure to me you bring,
Lilac blooming perennial and drooping star in the west,
And thought of him I love.
Walt Whitman, “When Lilacs Last in the Dooryard Bloom’d” (1865)
With the words of Walt Whitman, as he mourned the violent death of his beloved president, Abraham Lincoln, the lilac became eternally tied to spring, rebirth, cyclical time, and above all, the pain of grief. The common lilac (Syringa vulgaris), a native of the distant Balkan Peninsula, has become a much beloved ornamental species in the Northeast. Planted here since colonial times, its bright and fragrant blossoms mark the height of springtime activity, as trees leaf-out and animals rear their young.
Each year, the warming temperatures and longer days of May bring thousands of guests to the Arboretum’s historic lilac collection, which boasts over 375 plants representing 175 different taxa. Perhaps you’ve visited recently, to catch sight of the violets, mauves, magentas, periwinkles, and whites of lilac blossoms during these peak flowering weeks, and to enjoy the intoxicating scents on Bussey Hill Road. But did you know that the Arboretum is also home to two lilac plants that play a particularly important role for scientists across the country?
Syringa vulgaris (AA# 51-2012*MASS) and Syringa ‘Red Rothomagenesis’ (AA# 339-67*A) are two plants that are closely monitored for phenological activity every year. As part of the Cloned Plants Project, an effort of the National Phenology Network, these indicator species have provided over 50 years worth of phenological data. Chosen for their cold-hardiness, drought-resistance, and well-defined phenophases (leaf-out, flowering, etc.), lilacs are an excellent, non-invasive model organism. Cloned species provide the ideal solution to the problem of accounting for genetic variation among specimens. Because genotypes are identical among individual plants, we know that differences in the timing of phenological events are caused by local environmental conditions. Furthermore, the use of standardized, well-labeled indicator plants prevents the inaccuracies often introduced by observing native species.
Initial observations of lilacs began in the late 1950’s and were conducted by the U.S. Department of Agriculture (USDA) as an effort to better understand the life-cycle timing of certain crops and pests in order to increase yield. Early data sets incorporated lilacs in 12 states and depended on the work of over 2,500 volunteers. Today, the project has expanded to include over 300 sites tracking a variety of species. With the growing national interest in citizen science, the number of observation sites increases each year. As it surpasses its agricultural beginnings, the science of phenology has become an important contributor to climate change research around the globe. Data collected from lilacs and other cloned species helps us expand our understanding earth’s physical systems and the growing impact of climate change.
Just as Walt Whitman memorialized the flowering date of his mother’s Long Island lilacs in his moving tribute to Abraham Lincoln in 1865, citizen scientists can now observe the phenophases of their own cloned lilacs. To obtain a cloned plant and contribute to this important project, visit https://www.usanpn.org/nn/cloned-plants. NPN data sets are available to the public, and can be viewed using their handy visualization tool.
If you’re interested in learning more about phenology, botany, or ecology, join the Arnold Aboretum Tree Spotters, a group of citizen scientists responsible for collecting data from 11 species throughout the Arboretum. Read more about Tree Spotters in Silva [pdf]. Arboretum Members can join me on Tour H on Members’ Tour Day (Saturday, June 4th) to learn more about phenology and the history of data collection at the Arboretum. To register, email or call Wendy Krauss (617.384.5766).