Trees help to increase oxygen levels in the air, provide windbreaks, reduce soil erosion and shape the landscape. To commemorate the importance of trees, Texas observes Arbor Day on the last Friday in April, although individual cities in the state commemorate the day when it suits their climate best. The state geography is very diverse and there are many different types of trees that grow in Texas.
The pecan (Carya illinoinensis) is Texas's state tree. It is a large deciduous shade tree that can grow to 90 feet high and 75 feet across. Pecan trees perform best in rich bottomland soils, but will adapt to all areas in Texas. The pecan tree produces an edible nut that is enclosed in a thick leathery husk. The United States National Arboretum notes that Texans chose the pecan as their state tree in 1919 because in 1906, then-governor James Hogg made a deathbed request to have a pecan tree planted at his grave in place of a headstone.
Live oak (Quercus virginiana) grows to be 30 to 50 feet high but much wider, averaging 50 to 80 feet across. Live oak limbs grow first by sweeping close to the ground, and then upward. Live oaks are evergreen, losing and then growing leaves during a period of a few weeks in the spring. A live oak stands at the exact geographical center of the State of Texas, according to Texas A&M's guide to Famous Trees of Texas: "the Heart O'Texas Oak...stands at a point whose coordinates divide the second largest state in the Union into four equal areas."
The pinyon pine (Pinus edulis) grows in west Texas. It is a slow-growing evergreen with curved green needles. Wildlife eat the thin nuts that it produces. The Texas Tree Planting Guide characterizes the pinyon pine as a "living Christmas tree." It is relatively small, growing to between 10 and 30 feet high in a pyramid shape. Pinyon pines fare well in dry and rocky soils that are characteristic of high desert areas.
Texas ebony (Pithecellobium flexicaule) is a slow grower that attains a height of only 15 to 30 feet. During the summer months dense white and yellow blossoms cover the tree. The flowers are fragrant and appear to have a feathery spike. The tree bears small dark green leaves that fold up at night. Once established, Texas ebony requires very little water, making it a good specimen for drought-prone regions. The tree provides shelter for small mammals and birds. Birds eat its fruit and seeds. A Texas ebony, the Las Cuevas Ebony, stands at a popular border crossing between Texas and Mexico.