Andrew Bernier/KJZZ

Coconino National Forest.

Many Valley residents travel to Northern and Eastern Arizona for fall foliage. But what causes those colors?

Hiking in the inner basin of the San Francisco peaks, you’ll see the Aspens turn a brilliant yellow this time of year. If you can’t make it just yet, you can travel to lower elevation areas like Oak Creek Canyon, where leaves change later in the season.

Temperature and sun exposure are the main drivers for color change, but it turns out that the colors were there all along.

“A lot of people think that the leaves turn colors. But they don’t really turn colors as much as reveal what’s underneath."

Coconino National Forest Service's Brady Smith describes the revelation.   

“A lot of these leaves are yellow or orange in nature," Smith said. "And throughout the year they’re essentially through photosynthesis, that green color, through chlorophyll is provided because it’s being fed throughout the summer.”

As temperatures drop, trees form a cork-like substance over the small tubes at the base of the leaves that exchange water and sugar. Once water is shut off, the green chlorophyll pigment responsible for photosynthesis stops being produced, revealing the color of other pigments.