The leaves are turning from shades of green into golds, reds, oranges and yellows. To an artist or writer it signifies the mystical changing of the seasons. But to a forester, it is internal chemical process that manifests itself through outward expression.

There is a lot of science going on inside trees and shrubs in the fall, according to Cory Gregg, a resource forester for the Missouri Department of Conservation. However, he breaks it down simply.

First, sugars produced by photosynthesis are trapped inside leaves by chilly — but not freezing — autumn nights, he says. Those sugars are the building blocks for red, yellow, orange and purple pigments. Then cool nights simultaneously cause the breakdown of green pigments, allowing these other colors to show through. The result: vibrant fall colors.

When will they turn?
The reaction is happening across the state and even country. In Missouri, the fall-color season can last from four to six weeks, Gregg notes. And it happens to different tree species at different times and different locations.

For instance, beginning mid-September individuals may see sassafras, sumac and Virginia creeper start slowly changing colors. By late-September, black gum, bittersweet and dogwoods are turning. However, the biggest color burst peaks in mid-October. Gregg says this is when maple, ashes, oaks and hickories are at the height of their fall display.

The color change arrives first in northern Missouri and moves south. But you better take advantage of the view quickly because by late October the colors start fading and science once again takes over.

When the first chemical process takes place to change the leaf pigment, another reaction also occurs. Where the stem of the leaf attaches to the tree, a special layer of cells develops. Gradually, over the fall season, that severs the tissues that support the leaf. The leaf drops off. Before that happens, get out and enjoy the scenery.

Best viewing locations
MDC recommends routes along rivers with views of forested bluffs, and along ridges with sweeping scenes of forested landscapes. On a smaller scale, find fall color through drives on back roads, hikes, or float trips under a colorful forest canopy. Conservation areas and state parks are also great places to visit for fall color.

"Even treeless areas, such as prairies and roadsides, display beautiful shades of gold, purple, olive, and auburn with autumn wildflowers, shrubs, and grasses," Gregg says. "In cities and towns, enjoy places with mature trees, such as older neighborhoods, parks, and even cemeteries."

To help find the perfect color, the MDC offers weekly online fall color updates from department foresters all over the state. The updates include species of trees that are turning and recommendations for where to see them. Get fall color updates from MDC online at mdc.mo.gov/fallcolor.