An autumn leaf color flow and wave model was designed at the University of Georgia to illustrate what leaf experts call the fall color wave. Fall foliage color changes begin at high altitudes and latitudes and for all practical purposes move down-slopes and southward through North America.
This fall color change and flow takes place as three primary waves in mixed hardwood forests. The first wave is yellow dominated and you can expect to see yellow-poplar, birch, some maples and hickory, sassifras, sweetgum and aspens kick the season off. One exception here is sourwood where you can see it's red leaf in mid-September.
The second fall color wave is in orange. Some of the above species transition from yellow into orange but trees most noted for orange are silver maples and white oaks. Many people consider peak color occurring when this orange wave transitions into the third and final red wave.
This autumn color red wave of black tupelo, sumac, tallow tree, some oaks and maples signals the end of the fall display. After the red wave hits, the landscape slowly fades to brown.
On a single tree such as sugar maple, leaves of several colors can appear at the same time. Other tree leaves, like sweetgum, can actually change colors at different times depending on soil and weather conditions. Leaves of some species such as some elms simply shrivel up and fall off, exhibiting little color other than brown.