What Are the Differences Between Fan-Tex Ash & Arizona Ash Trees?

Arizona Ash

• The Arizona ash tree is sometimes called the velvet or desert ash. It is a fast-growing tree that can reach 50 feet tall when mature, with an equal or slightly smaller spread. It has a rounded crown, with 3- to 6-inch-long leaves made up of small leaflets that turn brilliant yellow in fall. Its inconspicuous green flowers, which appear in spring, are followed by winged fruits that persist on the tree, lasting for several months. The tree has smooth, gray bark when young, but its bark roughens and darkens as the tree ages. The Arizona ash tree grows in U.S. Department of Agriculture plant hardiness zones 7 through 11.

Fan-Tex

• The ash cultivar called "Fan-Tex" is also sometimes called "Rio-Grande." It's similar to the native tree in several respects, including its fast growth rate and mature size, which is usually about 40 feet with an equal spread. This cultivar has a slightly rounder and more broadly oval shape than the native tree, and its leaves are a bit glossier, but they also turn yellow in fall. "Fan-Tex" is a seedless cultivar so, unlike the Arizona ash, it doesn't drop winged seed pods during winter. The bark is nearly white, considerably lighter than the gray bark found on the native tree. Like the native tree, "Fan-Tex" grows in USDA zones 7 through 11.

Culture

• Both the native Arizona ash tree and the cultivar "Fan-Tex" thrive in full sun and tolerate a hot climate well. The trees do best when allowed to spread broadly, because a broad crown helps shade the trunk and protect it from sun scald, which can damage the bark in summer. A broad shape also helps slow evaporation of soil moisture and cools the tree's roots. These trees have good natural tolerance of dry spells or drought once well established, but grow best when given extra water during the first few years. They also grow in any type of soil, including alkaline desert soil, and can also grow in a moist spot but might be less vigorous under these conditions. If your soil is rich in clay and tends to drain slowly, mix in coarse sand at planting to improve drainage.

Problems

• Both types of ash trees have surface roots that can damage a foundation or lift paving, so they shouldn't be planted close to a building, patio or other paved area. They also tend to develop branches with narrow, weak angles of attachment, which can lead to branch breakage and decay of the resulting wound. This can shorten the tree's life, but pruning it every two or three years to remove potentially weak branches while they're still small can help prevent these problems. The trees are susceptible to scale, aphids and a bacterial disease called ash decline. You can treat for scale with horticultural oil spray, available pre-diluted at garden centers. Use insecticidal soap spray, diluted at a rate of 5 tablespoons per gallon, for aphids. Although ash decline is incurable, keeping a tree healthy and well irrigated helps prevent this disorder.