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the maturation of samaras, the elms’ winged fruits. Leaf out of the elms, along 
with the Common’s red maples, lindens (Tilia), oaks (Quercus), and scholar trees 
(Styphnolobium japonicum), follows over the next few weeks. As trees on the 
Boston Common respond to climate change in the future, ongoing photography 
may reveal that years like this become less anomalous. 
At the other end of the growing season, the deciduous trees of the Boston Com- 
mon start to prepare for winter by breaking down their photosynthetic machin- 
ery during the second half of October. The timing of those changes has not varied 
much over the last ten years. In the set of photos from 2018, for instance, we 
can see the visual transformation of the landscape that occurs each fall, with the 
faded greens of early autumn giving way to patches of gorgeous color, including 
yellow elms and reddish-brown oaks. Then, by the last week of November, the 
leaves have all fallen, exposing the scaffolding of branches that held them aloft 
all summer long. And at the tips of those branches are buds, poised to burst open 
in spring and start this cycle anew. 
Further reading 
Oswald, W. W. and Richardson, A.D. 2015. Tracking the seasonal rhythms of Boston Common 
trees. Arnoldia, 73: 36-39. 
Primack, D., Imbres, C., Primack, R.B., Miller-Rushing, A.J., and Del Tredici, P. 2004. Herbarium 
specimens demonstrate earlier flowering times in response to warming in Boston. 
American Journal of Botany, 91: 1260-1264. 
Richardson, A.D. 2019. Tracking seasonal rhythms of plants in diverse ecosystems with digital 
camera imagery. New Phytologist, 22.2: 1742-1750. 
Kelsey Allen is a student at Emerson College, studying literature and environmental science. W. 
Wyatt Oswald is a professor in the Marlboro Institute of Liberal Arts and Interdisciplinary Studies 
at Emerson College. He is a research associate at Harvard Forest. 
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