Eastern Redbuds in the Park - The young plant still has green leaves, while a nearby mature tree is leafless.

I find the studying of plant phenology to be endlessly fascinating. Have you ever wondered about how a tree loses its leaves? Does it lose them all at once or over a period of days or weeks? And which leaves fall first: the ones at the top or the ones at the bottom? Is there a pattern?

At one location I monitor in Marion County, Indiana, I've noticed that there is variation in the timing of leaf color change and leaf fall between mature redbud trees and seedlings. The mature trees changed color and lost all their leaves by mid-November. But the young trees, only a few seasons old, that sprouted from the fallen seeds of the mature, nearby trees, still have green living leaves. This gets me to wondering if this apparent age-related phenology difference is consistent for this species across locations or due to some quirk of the local environment. I also wonder whether sun exposure plays any role, because the young plants largely grew in the shade of their elders. Do plants in sunnier locations lose their leaves earlier than plants in shadier locations?

I've noticed a similar trend with Silver Maples in another location I monitor in Hamilton County, Indiana. While several forty- or fifty-year old trees have lost all their leaves, their four- or five-year old offspring still have leaves. Interestingly, some young trees growing in the fence line, that were cut back earlier in the summer, have even more live leaves that the other young trees. What accounts for this difference?

 

Young silver maples still have leaves while other nearby trees are bare.

Our programs have the potential to answer these questions and more.  Documenting phenology illuminates trends like these, which can prompt further study of the drivers of these trends and the underlying mechanisms at work. The closer we look, the more we notice and learn about the world around us.