Fall Color is Possible in South Texas
by Ro Wauer
One of my earliest memories of being raised in Idaho and Utah was the color of aspens on the mountainsides in fall. Great blotches of golden-yellow would dominate the landscapes, and I realized that winter was soon to follow. That brought snow and cold, but it also offered skiing, skating and sledding. Those activities also are but a memory, many of which I would as soon forget. And now living in South Texas, where fall color is barely noticeable, and snow is restricted to those very rare occasions, fall and its attributes require a little more imagination.
Fall color does occur in South Texas, however, although it is more subtle than it is to the north. Some of our broadleaf trees, such as some oaks, pecans, sycamore and cottonwoods, cypress trees, as well as a number of shrubs, do change color in fall. The reasons for the color change in our vegetation are the same as that to the north. It primarily is due to chemistry. Tree expert Robert Bartlett explained the process this way: "As summer wanes a band of tiny cells at the end of a leaf stem, where it hooks onto a twig, begin to dry and harden. This stops up the plumbing system inside the leaf. The manufacture of sugar slows down and the green chlorophyll no longer reaches the leaves. Now yellow pigments that have been masked within the leaves all summer are revealed. The red pigments are manufactured and the trees take on a kaleidoscope of hues and tones, a harmony of color."
Some of the eastern Native American tribes had a very different perspective on the fall color. They believed that leaf changes were due to celestial hunters who killed the Great Bear and that his dripping blood fell onto the forest trees, gradually changing the leaves to various shades. And although "Jack Frost," or the actual occurrence of frost, has little to do with the changing colors, weather is involved. If the fall is rainy, cloudy, or very hot, the foliage generally becomes bland, yellowish, or less vivid. Sugars, which are manufactured by the leaves, are transported down into the trees where they have little effect on fall foliage.
Locations and genetics are also significant in leaf color. The southwestern side of a tree usually has the deepest color since it gets more sunshine. And trees in lower places may show color earlier than those in higher spots if cold air settles in the low spots on still nights and the cooler temperatures trap sugar earlier. Genetic differences are also important. Typical red leaves are found in maples, dogwoods, and red and scarlet oaks, Browns and oranges are typical for white and black oaks, hickory, and hornbeam, while yellows are more prominent in cottonwoods, pecan, redbud, and elm trees.
Even though our fall colors are less dramatic than they are to the north, they still represent a change in season, a time to appreciate the end of hot weather and the beginning of mild winter days.