Plant Answers

Shumard Red Oak

Named after a Texas state geologist, Benjamin Franklin Shumard, Quercus shumardii is prized by homeowners throughout the South. In its favored habitat of moist bottomlands, the Shumard Oak may attain heights of 120 feet, although specimens of 100 feet are more frequent. As with most oaks in the red oak subgenus, Shumard oaks grow at a fairly fast rates With proper care, oaks will grow at a rate nearly equal to those trees perceived as fast?growing (i.e. Sycamore or Chinese Tallow). Other attributes include its ability to produce a spreading, symmetrical crown and its resistance to serious pests. Its finest quality, however, may be the scarlet hues this oak offers each fall. For transplanted Northerners as well as natives, a tree that provides consistent fall color is a tree to be treasured.

Still, the Shumard Oak is not without its faults. True Quercus shumardii is endemic only to those regions east of the Brazos River. Neutral or acidic soils and rainfall greater than 30 inches characterize this area of Texas. When these trees are transplanted in San Antonio, they often exhibit reduced growth rates and chlorosis, that is, yellow leaves. These conditions are exacerbated in areas where construction has occurred or where topsoil (in San Antonio this could mean anything) has been incorporated into the landscape. Both of these activities increase soil pH that, in turn, limits Shumard Oak's ability to absorb iron and manganese, resulting in the condition called chlorosis.

Some Shumard Oaks, however, demonstrate the ability to tolerate alkaline soils. Undoubtedly this is due to oak's extreme promiscuity. Oaks readily hybridize with other species in their own subgenus. Shumard Oaks often hybridize with Texas Red Oaks, Quercus texana, resulting in a tree that tolerates alkaline soil better than its parents. Botanists constantly quarrel over whether or not Quercus texana is actually a variety of Quercus shumardii. Who cares? We should be concerned whether or not the species will grow well in South Central Texas. Some Red Oaks under the generic name of Shumard may be able to accomplish this feat.

Although Shumard Oaks has some serious faults, let's not throw the baby out with the bath water. Shumard Oak is still a good tree for this area within certain parameters. When purchasing a Shumard Oak, homeowners should ask where the seed was collected—the farther west, the better.

Regarding the native range of Shumard Red Oak, Robert Vines (in Trees, Shrubs and Vines of the Southwest) indicates that it is native on moist hillsides or bottom lands in clay soils in Central Texas, Oklahoma and Arkansas; eastward through Louisiana to Florida; northward to Pennsylvania and west to Kansas. Correll and Johnson (in the Manual of the Vascular Plants of Texas) lists its native range to moist forests in the timber region of East Texas and west along waterways to the escarpment of the Edwards Plateau. The problem with Shumard Oak is that much of its native habitat is in the East in acid soils. Shumard Oaks collected and sold from these acid, high rainfall areas do not do well here. But there are many Shumard Red Oaks growing on highly alkaline soils, similar to those of South Central Texas, in a line running from La Grange through Brenham, Navasota, and College Station, up to Dallas. These areas all also have severe problems with iron chlorosis, yet the Shumard Red Oak thrives there. This is where acorns should be gathered to produce trees for planting in our alkaline soils.

To sum up the confusion with Texas Red Oak (Spanish Oak) and Shumard Red Oak—when looking at a state map, Texas Red Oak is native west of I?35 and Shumard Red Oak is native east of I?35. Although closely related, in its true form, Texas Red Oak is a small, lacy leafed tree with small acorns, while Shumard Red Oak is a tall, large?leafed tree with large acorns. What makes all of this so confusing is that along this I?35 line, these two trees hybridize readily and show characteristics of both species.

Texas Red Oak

Contributed by Mr. Manuel Flores

We can be so unreasonable when it comes to horticulture. We plant $20 trees in $1 holes and expect great results. Some of us search for that mythical dwarf, evergreen shrub that blooms year?round in dense shade. And then there are those who choose to live in South Central Texas to enjoy the usually mild winters, but also want our trees to shed their foliage as spectacularly as the maples of Vermont.

Though the effect will not rival a New England postcard, our flame?leaf fantasies can be realized even here in San Antonio. One of the best providers of consistent fall color is a native. It is variously called Spanish Oak or Texas Red Oak (Quercus texana). Texas Red Oak inhabits the rocky slopes of the Hill Country and the canyons of the Edwards Plateau. It is, in its typical form, a multi?trunked specimen of rugged beauty. Its unique character is the result of years of drought, fires and poor, shallow soils. This native, however, is readily domesticated and is capable of growing 4 feet each year.

Until recently, those wanting the genuine Texas Oak had to buy balled and burlapped specimens. Now, progressive wholesale nurseries are producing it in 1, 5, and 15 gallon containers. Unlike the balled and burlapped trees, the container?grown trees suffer no transplant shock and can be planted safely at any time of the year.

Yes, I know some of you acquired container?grown "Red Oaks" 5 to 10 years ago. Have you noticed their foliage is always a sickly pea?green? In other cases, the leaves have brown margins or, even worse, were at first the palest possible green and later completely scorched. If your "Red Oak" resembles (or resembled) my description, you unfortunately have an eastern type Red Oak (Northern Red Oak, Scarlet Red Oak, Southern Red Oak, Water Oak, or an eastern grown or collected Shumard Red Oak). We unkindly refer to them as 500-pound azaleas. In shallow, rocky, alkaline soils, these are doomed to fail. They can only be grown in acidic soils.

Consider enhancing your landscpape with a Texas Red Oak (Quercus texana). Remember to plant it in well-drained soil and at least 25 feet away from any structures (in my book, a driveway is also a structure). Of course, you must also promise to provide the young Texas Red Oak with a 4-foot diameter mulched bed. Slow-release fertilizers are quite beneficial as is a thorough soaking every two weeks during the first two growing seasons.