FOLIAGE: Penn State University is reporting predictions of a “banner year” for fall foliage in Pennsylvania.

“The rainy summer in Pennsylvania has set the stage for what could be an awesome autumn foliage display, according to forest ecologists in Penn State’s College of Agricultural Sciences,” the university announced.

The set-up is good, but a beautiful autumn display is not a guarantee.

Marc Abrams, professor of forest ecology and physiology, explained, “The cool, moist summer should usher in great fall colors. The robust physiology of the trees this year should predispose them to producing good color.”

Kim Steiner, professor of forest biology, said the fact that the leaves didn’t start to change early is a good sign.

The temperature in the coming weeks may be what makes or breaks the display this year, according to Abrams.

“What we need now is for cool to cold temperatures to arrive by early to mid-October to bring out the best colors,” he said. “Unless things go haywire with the weather — with unusually warm and wet conditions — it should be a fine year.”

A statement from Penn State described the biological process that produces the bright colors.

“Cooler temperatures signal deciduous trees to stop producing chlorophyll, the green pigment responsible for photosynthesis,” it read. “The chlorophyll breaks down and disappears, unmasking other leaf pigments. These other pigments — called xanthophylls and carotenes — are what create the yellows and oranges seen in the leaves of yellow poplar, hickory, sycamore, honey locust, birch, beech and certain maples.”

Reds and purples can be seen in maple, sassafras, sumac, blackgum and scarlet oak trees when they produce the pigment anthocyanin after they stop producing chlorophyll, Abrams said.