Fall colors to adorn Texas soon

Wednesday, September 17, 2003

The arrival of gold, red and orange fall colors, splashing across the Texas landscape, is always a welcome site. Although fall in Texas is not as stunning as fall in the New England states, Texas can boast of spectacular foliage, according to a University of North Texas botanist.“Fall color development is complicated and extremely fragile,” says Dr. Don Smith, professor of biological sciences. “Success depends on everything happening in exactly the right sequence of time.”Smith says trees are able to recognize that autumn is coming when days become shorter and temperatures begin to drop. This signals a decrease in chlorophyll production — the green pigment that carries out photosynthesis. With less chlorophyll, other colors in the leaves become prominent. “More processes besides cool nights and shorter days must occur before the color season is able to take place,” Smith says. “Texas tends to be dry during the fall season. This condition increases the speed with which leaves drop from trees. Intense fall color cannot occur, if leaves drop too fast.”Smith says a rainstorm or afternoon of heavy wind in late fall — late October through Thanksgiving — could also send all leaves to the ground. He says rain needs to come followed by sun, because trees need sunny weather to develop color. If rain is too late in the season, there won’t be any color. Texas normally has warm nights in the fall. Warm nights cause trees to move sugars — the tree’s primary nutrients — from leaves to the root system for winter storage. When this occurs, leaves don’t change colors. Cold nights, however, slow down the process of moving nutrients from leaves. With the process slowed, sugars remain in leaves for a longer amount of time, producing brilliant colors. However, when nights get too cold, freezing temperatures destroy the leaves ability to produce pigments, so leaves turn brown overnight. Smith says certain types of trees are more likely to produce colorful leaves regardless of weather conditions. Red oak, red tooth maple, crepe myrtle and sweet gum trees will have beautiful pigmentation every fall, he says. Other trees produce color only on good years. Trees such as cedar elm and cottonwood fit into this category.Smith points to a variety of trees in different regions of the state, which produce spectacular fall colors.“The farther north you go in Texas, the better your chances for seeing an abundance of fall colors, because of cooler weather,” he says. “Fall colors are not as pronounced in the Southeastern areas of Texas as they are in Northeast Texas. In East Texas, particularly the Big Thicket area, color will be displayed in Shumard oaks, sweet gum and red gum.” Smith says some cities in West Texas, particularly Lubbock, have a good number of red oaks and a water supply to foster healthy trees with beautiful colors. In fact, says Smith, all urban areas will have greater fall color, because people in cities and suburbs water trees. If the trees are in the yard, homeowners can supply the water and ease problems caused by dry summers and falls. Finally, Smith reveals a way to trick nature. “If you want to keep leaves on your trees for a longer amount of time, plant them near street lights. The artificial light mimics the sun, extends the apparent day length, and keeps leaves on the tree longer,” he says. He adds the early predictors for good fall color are favorable this year.“Soil moisture is reasonable in most locations, temperatures are lower than usual and cooler-than-normal nights are occurring,” he says.

UNT News Service Phone Number: (940) 565-2108

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