Three oaks - the Shumard red oak, live oak and bur oak - are all shade trees native to South Texas. Each of these oaks can reach a minimum height of 40 feet; the live oak and bur oak can grow as much as 50 feet tall and the Shumard up to 60 feet. Shade coverage provided by these drought-loving trees can span as much as 40 feet (Shumard red oak) to 100 feet wide (live oak).
The Shumard Red Oak can grow even in somewhat alkaline soil. According to Plant Answers, it is the Live Oak that is rated the best tree to plant for San Antonio and other southern Texas cities.
Drummond Red Maple
You can plant the Drummond red maple shade tree if you have acidic soil in your part of South Texas. This shade tree can reach between 50 to 70 feet (100 feet in the wild). Canopy spread width can reach as much as 60 feet, making the Drummond red maple a good shade tree choice for his part of the state. According to Texas A&M, the Drummond red maple is the most common to the southeastern portion of Texas but doesn't handle drought very well.
South Texas green ash shade trees reach up to 70 feet tall and sports bright green leaves which turn yellow in the fall--and sometimes purple, according to the Texas Bayou Region Tree Guide. This tree can be planted if you have clay, sandy or silty soils and is considered the most adaptable of the ash trees.
If space is a limitation in your landscape but you still want a shade tree, choose a Texas olive tree. The Texas olive tree produces flowers almost year-round, with large attractive blossoms. Your tree will not grow more than approximately 15 feet, but the shade span is up to 10 feet, making it ideal for those with limited space in the landscape.
Well-drained soil is a necessity with this tree, and it is becoming more rare to see a Texas Olive Tree in Texas, according to the San Antonio Express News