Keith Hansen

Fall is a wonderful time of year. Many changes are in the air, especially with our trees. East Texas has its own color to rival many parts of the country. However, it can be different from year to year.

The intensity of fall leaf coloration depends on certain combinations of environmental conditions - bright, sunny days, combined with cool, crisp nights. This promotes the accumulation of carbohydrates that develop into the bright reds and purples in certain species.

Since our fall weather varies from year to year, the annual fall color display, even for the same tree, can vary as well. Also, if trees are under drought stress, fall color can be disappointing, while a very wet fall can also reduce the vibrancy of the color.

In most types of trees, browns, yellows and oranges develop as the leaf gradually dies in the fall. During this process, the dominate, unstable green pigment in leaves called chlorophyll breaks down, revealing more stable yellow/orange pigments, called carotene and xanthophyll, that have been there all along.

Red pigments in leaves are called anthocyanins. These are produced in the fall when the sugar content of the cell sap is high. This requires bright sunlight, so a cloudy fall can reduce red coloration.

Soil pH also plays a role, especially in red maples where they turn brilliant red in acid soils but only yellow in neutral or alkaline soil. However, some varieties are clonally propagated and dependably turn red no matter what soil they are in.

If you're looking for trees for your yard, fall is a good time to visit nurseries as their stock turns colors. Most, but not all, trees are grown from seed, so there will be variation from tree to tree in its fall color.

There are several trees species which dependably light up the landscape for several weeks in East Texas with colorful foliage.

Yellow: (Ginkgo biloba) For bright yellow, nothing beats the beautiful ginkgo, also called maidenhair tree. There is nothing dull about this fall display. This large shade tree turns bright canary yellow in the fall, and when it decides to drop its leaves, it does it all at once - none of this raking for weeks and months on end. Ginkgo is a long-lived, disease and insect resistant tree. There are several nice specimens scattered around the Tyler.

A great place to see mature specimens of ginkgo is the Tyler City Hall. On the southeast corner of city hall there is a 125-year old ginkgo, called the Hubbard Ginkgo. A large, but much younger specimen (about 50 or 60 years old) can be seen on the north lawn. Another place to view gingko trees is at the Ina Brundrett Azalea Garden located on the Tyler Junior College Campus.

There is an alee of about 14 Sentry ginkgos planted on either side of the sidewalk between Jenkins Hall and Wise Cultural Arts Building. The Sentry variety has a very narrow, upright growth habit, unlike the common ginkgo with a more spreading habit. This should also be a good time to view the fall display of the large collection of Encore azaleas in that garden.

Red: Some of the best reds include blackgum (Nyssa sylvatica), red and white oak (Quercus), and sweetgum (Liquidamber). These are usually the first to change color. Red maple (Acer rubrum), and dogwood (Cornus florida) also display shades of red from wine to scarlet. Some of the red maple varieties you might find at some nurseries include "October Glory,'' "Red Sunset.'' and "Autumn Fantasy'' (a red and silver maple hybrid).

Blackgum has one of the best dark scarlet red displays in the fall. It is also one of the very first trees to turn color in the woodlands each fall. It is hard to transplant from the wild, but you should be able to find blackgum in containers at nurseries ready to transplant.

Orange: Texas Extension horticulturists picked as a Texas Superstar an outstanding tree for the Texas landscape. The Chinese pistache (Pistacia chinensis) is an excellent, medium-size tree with an attractive rounded shape. For a dependable display of orange, red-orange to crimson, Chinese pistache is hard to beat. A good example of two trees can be seen in Tyler at the corner of Troup Highway and Beckham Avenue near the fire station. Japanese persimmon not only provides delectable fruit, but also a brilliant display of fall color of bright orange (to match the fruit), reds and yellows. Native persimmon trees also color up the roadsides and woods in the fall with red, yellow and orange foliage.

Japanese maples are a special group of trees, and most of them provide outstanding color every fall from bright yellow to pumpkin orange to scarlet. Mature sizes range from 4 feet to up to 20 feet tall. There are many varieties, but any Japanese maple is worthy of a prominent spot in the landscape. We are fortunate that we have good conditions for growing these highly ornamental trees, and many wonderful specimens can be easily spotted driving around Tyler in the fall. The Tyler Rose Garden, with a collection of over labeled 30 varieties, is good place to see these beautiful plants.

Shrubs for Autumn Color: Besides trees, many shrubs provide a burst of color in the fall. Here is a sample to consider: Azalea (Rhododendron) - varies; Blueberry (Vaccinium) - orange/red; Farkleberry (Vaccinium arboreum) - orange/red; Oakleaf Hydrangea (Hydrangea quercifolia) - burgundy red; and Virginia Sweetspire (Itea virginica) - varies- red/orange/yellow.



Keith Hansen is Smith County Horticulturist with Texas Cooperative Extension. His Web page is http://EastTexasGardening.tamu.edu Texas Cooperative Extension educational programs are open to all individuals without regard to race, color, sex, disability, religion, age or national origin.

Keith Hansen
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