The Texas ash tree and the Arizona ash tree share many similar traits. Both are deciduous trees that are hardy in two of the same zones. The Texas ash tree is hardy in zones 5 -- 9A, while the Arizona ash tree is hardy in zones 7 and 8. When comparing trees there are several important factors to consider, such as size (height and spread), growth rate, flowers and fruit, structural concerns, and any known disease or pest problems.
When it comes to size the Arizona ash tree has a larger spread than does the Texas ash. A mature Arizona ash tree can have a spread of 45 to 60 feet, whereas a mature Texas ash tree can have a spread of 25 to 35 feet. Both trees will reach similar heights, with the Texas ash tree reaching a height of 30 to 40 feet, and the Arizona ash tree reaching a height of 30 to 50 feet. So, if you are limited in space (when it comes to the width) then it would appear that the Texas ash would be the tree of choice.
The Arizona ash is known for its fast rate of growth, while the Texas ash's growth rate is slow. Since both trees are used as shade trees in landscape design, then the Arizona ash would grow quicker and provide shade faster than the Texas ash tree.
Flowers and Fruit
Flowers and fruit may or may not attract a variety of wildlife. Flowers can provide beauty to the tree, and both flowers and fruit can become a litter problem. The flowers and fruits of both trees are not known to attract wildlife. However, the flowers of the Arizona ash tree are quite showy as compared to the Texas ash. Litter from the fruit, twigs, and foliage can be a problem with the Arizona ash tree -- this creates a high maintenance situation for the homeowner.
When comparing both trees the Arizona ash has serious structural concerns. The tree develops several upright trunks, all the trunks stem from the main trunk, originating from the same location -- this makes the tree very weak, which leads to a shorter life expectancy. The Texas ash tree does not have these structural concerns. Although it can grow with multiple trunks, they do not weaken the structure, and they can be trained to grow with a single trunk.
Diseases and Pests
Both trees are susceptible to verticillium wilt, which is a systemic disease caused by a soil-borne fungus. This disease is serious and is comparable to Dutch Elm disease. Verticillium wilt can cause minor or major damage to a tree, depending upon its severity, and it strikes at anytime during the growing season. A severe case of verticillium wilt will kill the tree in its completely. The Texas ash tree is generally not affected by pests. However, the Arizona ash tree is very sensitive to pests such as borers, which can be a very serious problem.
All factors taken into consideration, the Texas ash tree appears to be a better choice, although it grows slower than the Arizona ash tree it is not riddled with the structural, litter, or pest problems that the Arizona ash tree is known for.