LEWISBURG, Pa. — If it seems that fall foliage color is a bit mixed this year — with many trees dropping their leaves before reaching peak color — that’s because environmental factors affecting foliage brilliance have been a bit mixed too, according to Bucknell University Professor Chris Martine, biology. He points out that good fall colors require a combination of three factors.
“You need pretty good moisture, relatively warm days and really cool nights. We’ve had lots of moisture and relatively warm days, but only recently have we started getting cool nights,” says Martine, the David Burpee Professor in Plant Genetics & Research. “Without those three things in combination, your fall color tends to not be that great, and many trees drop their leaves without ever really hitting that peak color we often get.
“This year we also had very little rain in the early part of the summer, which likely affected how robust the connections between leaves and their branches were. Even after all of the late-summer and fall rain we got, this probably means that leaves will drop off pretty quickly once a few cold days show up.”
Martine has also observed that global climate change has played a hand in changing the environmental clock on peak fall foliage in recent years.
“If we continue to get weather like we’ve had the last couple of years (warmer), we get really late color change and then a shift when we see the first frost, which to me was always early November,” he says. “If that continues, we will see a shift in when that color change occurs and how deep it is in some parts of the country.”