FALL COLORS, AND HOW THEY OCCUR
Is Jack Frost really responsible?
Jim Eagleman
Photography by John Maxwell
September/Ocbotber 2007
We’ve all heard versions of the Jack Frost story and his coloring of fall leaves. As the weather gets cooler with each autumn day, we can almost imagine his nightly visits with pallet and paintbrushes in hand. But scientists tell us that the changing of leaf color has something to do with warm days, nightly frost, and the amount of daylight. To understand how fall colors appear, let’s look back to the tree in mid-summer.
As the leaves twisted in the summer breezes with bright sunshine overhead, they produced a substance called chlorophyll. This green color pigment in the tiny cells of leaves gave us a shady summer ceiling of shimmering layers, shapes and textures in the forest. Think of chlorophyll as a mask, like a Halloween mask. Hidden behind the green color of the chlorophyll all summer were other colors that were masked, or hidden from view.
As fall approaches, temperatures cool and daylight hours shorten. Production of new chlorophyll begins breaking down and slowly disappears as fluids are withdrawn from the leaves. The green color in the cells begins to break down and the color show we are used to seeing really begins.
The red color we see in red maple leaves is called anthocyanin.
The yellows and oranges of sassafras and the maples, and also known to occur in bananas and pumpkins, are due to the pigment carotene.
In oak and hickory leaves, the chlorophyll simply fades from tans to brown, produced by tannins that we find in teas and coffees.
Levi and Michaiah Blackwell from Beech Grove collect leaves for tracing (above).