Fraxinus velutina, also called Arizona ash or velvet ash, is a deciduous tree native to Texas, Arizona, New Mexico, California, Nevada and Utah, where it grows in canyons, along desert stream banks and near moist washes. Arizona ashes are commonly planted as shade trees in residential lawns and parks, in parking lot islands, and along highway medians or roadsides.
Arizona ash trees vary in height from 30 to 50 feet, with a 45- to 60-foot spread depending on their growing conditions. They have spreading, open crowns and single or multiple trunks with deeply furrowed bark. Their opposite green leaves turn yellow in the fall; the leaf shapes vary depending on the tree. Arizona ash trees produce ornamentally unimportant green or greenish yellow flowers, according to Edward F. Gilman and Dennis G. Watson from the University of Florida IFAS Extension; tan or green winged seed pods replace the flowers.
Cultivating Arizona Ash
Arizona ash trees can grow in a variety of soil types. These trees have a high tolerance for drought, but they can also grow in wet or poorly-drained soils. They propagate easily by seeds, as well as grafts and cuttings. They can tolerate desert and alkaline soil. Several Arizona ash cultivars include Modesto and Rio Grande fantex ash. They prefer full sunlight, although trunks may be susceptible to sun scald in harsh desert environments if they have light canopies.
Arizona ash trees have a rapid growth rate. This encourages the development of surface roots that damage surface structures, such as sidewalks and walkways. The trees are difficult to maintain because multiple trunks often form from the main trunk. This creates weak trees that break easily at the base. They also require regular pruning to keep their branches from breaking or dying. They tend to be messy, and leave seed pods and leaves on the lawn. Arizona ash trees only survive for 25 to 30 years before dying.
Pests and Diseases
Arizona ash trees are susceptible to attacks from aphids and scale insects. Aphids have small, pear-shaped bodies, and vary in color depending upon the species and what the insect has been eating. Scale insects have round or oval-shaped protective coverings over their bodies. These insects drain sap from plants but rarely cause serious damage. The Verticillium dahliae and Verticillium albo-atrum fungi cause verticillium wilt in ash trees. The fungus attacks the roots and releases toxins that clog up the tree's water transport system, causing discoloration in the sapwood, branch dieback and tree death.