Monitoring Fruit Phenology at the Arnold Arboretum and Beyond

Posted by Amanda Gallinat

"This crop grows wild all over the country—wholesome, bountiful, and free, a real ambrosia."

-Henry David Thoreau, Wild Fruits

In addition to observing flowering and leafing out times of wild plants in Concord, Thoreau also took an active interest in fruit phenology. Fleshy fruits that ripen in late-summer and autumn provide food for animals like migratory songbirds, which in turn disperse the seeds of the fruits they eat. Despite the importance of fruits, surprisingly little is known about how much variation exists in the fruiting phenology of different species, how native and invasive species differ in their fruiting phenology, or how fruit ripening times are responding to climate change.

An American Robin (Turdus migratorius) consumes the fruits of a non-native crab apple tree at the Arnold Arboretum in Boston, MA

This autumn, the Primack Lab began a new endeavor: to track the fruiting times of over 250 species at the Arnold Arboretum in Boston, MA. Every ten days, members of our lab ventured into the arboretum with the goal of documenting the first and last fruiting dates of species across the vast collections of fleshy-fruited plants. We will use the data gathered this season and in future seasons to assess the variation in fruiting phenology among an exceptionally broad group of species, and we hope to compare our observations to those recorded at other arboreta across the world. 

Amanda Gallinat collects information on fruiting times in the Viburnum collection of the Arnold Arboretum 

Our monitoring at the Arnold Arboretum is complemented by our observations of native and invasive fruiting species at Manomet Center for Conservation Sciences in Plymouth, MA. There we are investigating seasonal changes in fruit availability for migratory songbirds, differences in the seasonal profiles of native and invasive fruits, and how songbird diets (which are primarily composed of fruits in autumn) have changed over the past 25 years. 

Fleshy fruits of American Pokeweed (Phytolacca americana) at different stages of ripeness at Manomet in Plymouth, MA