Tree leaves contain cells that create food for the whole tree. Those cells use chlorophyll, which gives leaves their green color. The chlorophyll absorbs energy from the sun to turn water and carbon dioxide into sugars and starches -- food for the tree.
Even though green is what you see during the growing season, there are also hidden colors in the leaves. These are called cartenoids. They're the crystaline color pigments that give yellow and orange hues to plants such as carrots, corn and daffodils.
In the fall, shorter days and cooler nights mean there's less energy for food-making. The chlorophyll starts to break down, so the green slowly disappears and the yellow cartenoids finally make their appearance in trees such as hickory, ash, birch, maple, sycamore, cottonwood and sassafras.
Unlike gold and orange, the red and purple colors aren't hiding in the leaves. They're newly created in the fall when sugars are made during warm days, then trapped in the leaves during cool nights. The trapped sugars change chemically into anthocyanins which appear as reds and purples.
The more sunshine during the day, the more red color is created. That's why shaded leaves will be less red than those that get lots of sun. If the weather is cloudy and the nights stay warm, there won't be as much vivid color in such trees as the maple, sweetgum, oak and dogwood.
Aside from contrasting temperatures, other factors can affect fall color. Trees that don't get enough water during the growing season may just drop their leaves quickly before they color. Severe cold will kill leaves before they have time for a fall display.
You can find out where the peak fall colors in Missouri are by logging on to the Missouri Conservation's Web site at www.missouriconservation.org.