Arizona AshFraxinus velutina) are quite common in Arizona and adapt well to sunny weather here. In fact, many other types of ash grow in Arizona as well. There are more than 65 species of ash trees. Wikipedia lists many ash trees according to the regions where they are found. Note that there are other woody plants that have “ash” in their name (such as mountain ash and prickly ash), but they are not of the genus Fraxinus, so they are not varieties of ash at all. Below is a list of some of the Arizona ash varieties, which is by no means complete:
- Green ash (Fraxinus pennsylvanica) – also called ‘swamp ash’ or ‘water ash’
- Raywood Ash (Fraxinus oxycarpa)
- Shamel ash, (Fraxinus uhdei) – also called ‘tropical ash’
- Fresno Fantex, (Fraxinus velutina) – also called ‘Fresno de Río Grande’
- Small leaf ashFraxinus greggii)
- Arizona AshFraxinus velutina) – commonly known as ‘velvet ash’ or ‘modest ash’
- One-leaf ash (Fraxinus anomala)
- Goodding ash (Fraxinus gooddingii)
- Fragrant ash (Fraxinus cuspidata)
- Chihuahua ashFraxinus papillosa)
Arizona ash has many positive characteristics, but along with them come some drawbacks. Horticulturist Calvin R. Finch, Ph.D., has labeled the Arizona ash a ‘garbage tree’ due to its lifespan of only about 25-30 years, among other reasons.
Ash trees are deciduous, which means they lose their leaves at the end of the growing season. Many types of trees are considered cluttered and ash is no exception. Fortunately, most ash trees limit their leaf drop to a period of two weeks. Most ash trees also produce seedlings, either year-round or just once a year, but in large numbers depending on their genus and species. With an ash tree, you should learn to enjoy raking at least once in a while if you prefer a neat garden.
Most species of ash are fast-growing trees. While rapid growth creates a quick shade, it also has drawbacks. Fast-growing trees tend to develop shallow roots. Although ash roots often grow close to the surface, they are generally tolerant of both alkaline and rocky soils.However, as Watson and Gilman describe in their fact sheet on green ash, these shallow roots they can “become a nuisance as they raise curbs, sidewalks and make mowing difficult.” Finch is quick to point out another drawback to the rapid growth typical of most ash trees: “Unless you prune it regularly, it can become a mess with frequent branch dieback.” Plan to prune ash trees at least every few years to promote a healthy branch structure and prevent your canopy from becoming too dense. Otherwise, there may be weak growth that is prone to breakage. It is not a good idea to allow multiple trunks as this will eventually lead to structural failure. It is best to establish a central trunk while the tree is still young. Before planting a new ash tree, make sure your garden is large enough. Ash trees are large trees. While most mature ash trees reach around 40 to 50 feet tall, some can be over 80 feet tall and all tend to have a full, round canopy.
Arizona ash trees, like many other plants, are susceptible to various pests and diseases. These include canker, mildew, and various fungal infections, leaf burns, rust diseases, and pests such as spider mites, fabric worms, woodworms, and borers. Ash trees are particularly vulnerable to Verticillium wilt, which is a soil-borne fungus. In some parts of the country (primarily the Midwest), the emerald ash borer has killed many tens of thousands of ash trees. Fortunately, Arizona ash varieties have yet to be affected by the destructive emerald ash borer (read more about this pest at http://www.emeraldashborer.info). Trees that endure poor environmental conditions are more vulnerable to these problems, so it is important to keep the tree’s defenses high by watering and fertilizing properly.
In your effort to maintain your Arizona ash, I encourage you to do your research by species, because there is a surprising variety of unique qualities attributed to each one. There is a series of several hundred fact sheets on tree and shrub species, written by Edward F. Gilman and Dennis G. Watson, both professors at the University of Florida. These are a good source of basic information on the specific trees that you may want to learn more about. They are provided in part by the Forest Service and the US Department of Agriculture.
If kept well, ash trees are very lush and beautiful. On the other hand, ash trees that are not easily cared for become an eyesore and are much more likely to harbor various tree pests and diseases. While certain varieties of ash are quite resistant to drought, most require a lot of water. Flood irrigation will provide the best setting for an ash tree. If your garden is not watered, it is best to mimic flood irrigation with your garden hose by watering it deeply once or twice a month. If you live in Arizona and have an ash tree in your yard that you hope to keep healthy and looking good, be prepared to shrink when you look at your monthly water bill. You may also want to fertilize your ash trees regularly. Mulching around the tree is also beneficial for two reasons: Not only will it enrich the soil as organic matter breaks down, but the mulch will also retain moisture from irrigation to keep the soil moist longer.
Although they are not especially easy to care for, it is worth the effort to keep every ash tree in your yard healthy. In exchange for your service, they will provide you with plenty of lovely shade. A healthy Arizona ash is sure to enhance the beauty of your garden.