Fall foliage is expected to be especially bright and colorful this year because plentiful summer rains, followed by September’s warm days and cool nights, have kept the leaves on the trees longer than drier seasons, says a Penn horticulturist. 

“It sets up the perfect conditions for trees to have the maximum fall color,” says Anthony S. Aiello, the Gayle E. Maloney Director of Horticulture and Curator at the Morris Arboretum. “It looks like it’s going to be nice.”

Penn’s campus and the Arboretum have a great diversity of trees that will peak at different times in October to provide weeks of colorful fall foliage.

“But these things, like the weather, are unpredictable,” Aiello says. He says the lack of rain in the first few days of October could possibly temper the intensity of color for leaves on some species, primarily the reds of the sugar maples, “but expected rain the next few days should alleviate any impacts on the show.”

Onset of autumn color starts north and travels south, and comes earlier in higher elevations. Aiello says the last two weeks of October and even the first days of November are the peak periods for Philadelphia.

The earliest native tree species to change color are starting now, he says. First are dogwoods, which start out with a deep burgundy and transition to brighter reds, oranges, and yellows. Next are sugar maples, with reds, yellows, and oranges, followed by the bright red of the red maples. The great oak trees transform in the last wave.

Aiello’s favorite is the tupelo, Nyssa sylvatica, otherwise known as the black or sour gum tree.

“They are really spectacular, a kaleidoscope of color,” he says. “The range of colors reminds me of a stained-glass window in a gothic cathedral. The leaves are small and you get a big array of colors.”

Penn’s website has online “plant locators” for both the main campus and the Arboretum.

“You can type in ‘red maple,’ and the map will show you the locations of all the red maples,” Aiello says. For those looking for his favorite, there are two tupelos near College Green, and three near the Arboretum’s rose garden.

Now in his 18th year working at the Arboretum, Aiello says spring is his favorite season.

“The hopefulness of spring, the vibrancy and fresh green colors, as a horticulturist, that’s what you live for, is to see the season start again,” he says.

But fall is a close second.

“Each fall, there’s this moment where everything is right: the air temperature is right, the sun is right, and you are captivated by something that you see,” says Aiello. “It’s just a moment when you think, ‘This is the perfect moment.’ That is what I cherish each year.”