If you’re looking to plant a shade tree in the desert that has beautiful fall colors, Arizona ash is one to consider. Here’s everything you need to know about planting and caring for this native, desert-adapted tree.
Arizona ash (Fraxinus velutina) is a large, deciduous shade tree that turns golden-yellow in the fall. It is native to parts of California, Arizona, Utah, Nevada, and Texas.
While this southwest native can withstand the desert’s extreme temperatures, it is not a desert tree. In the wild, it grows in canyons and along streams, and its presence usually indicates a stream or other permanent water source. Along with cottonwoods and willows, it is an indicator that there is water.
It can be found growing in areas with as little as 5” annual rainfall and as much as 62”.
So Arizona ash requires more water than typical desert trees, especially when young,
Arizona ash is a boon to wildlife. The flowers are inconspicuous to the human eye but attract bees and butterflies. The leaves provide larval food for dozens of species of moths and butterflies, and the seeds provide food for seed-eating birds.
Why I Like This Plant
- Beautiful large shade tree
- Provides golden fall color
- Withstands extreme temperature changes
- Grows relatively fast
- Beneficial for birds, bees, and butterflies
Things to Watch Out For
While Arizona ash is clearly a desirable shade tree, it does have some issues to be aware of.
- Arizona ash is considered a high-allergen tree, so you might want to skip this if you have tree allergies. It’s in the same family as olive trees (Oleaceae) which have been banned from growing in some parts of the southwest due to their highly allergenic nature.
- It’s a moderate (rather than low) water use tree. The Southern Nevada Water Authority only gives Arizona ash two stars out of five on “climate resiliency.”
- It is subject to several diseases and pests, which are discussed below.
Optimal Growing Conditions
If you’re thinking of adding an Arizona ash to your garden, you need to find a suitable place that will keep your plant healthy and looking good… while minimizing maintenance for you.
Here are the key factors to keep in mind.
Temperature
Arizona ash should be grown in USDA Hardiness Zones 6 – 11. It is very cold-hardy, surviving temperatures as low as -10℉.
Sun Exposure
Arizona ash can be grown in either full sun or part shade. It’s prone to trunk sunscald in hotter climates, so it is best to provide some relief from intense afternoon sun and keep it away from walls where it will get reflected heat.
Size and Growth Rate
Arizona ash is a moderately fast grower and can reach a mature size of 40 feet tall by 30 feet wide in its natural habitat. When cultivated, it often does not get quite this big, but it is still a substantial tree that needs plenty of room to grow.
Soil
Arizona ash is not fussy about soil type or pH. It grows equally well in all kinds of desert soil — sand, clay, or rocky. And while it needs a moderate amount of water, the soil needs to be well-drained or it can develop root rot.
Pests and Diseases
Arizona ash does face a few pests and diseases. If overwatered, it is susceptible to root rot.
Arizona ash is prone to a bacterial disease known as ash decline that is transmitted from plant to plant by sucking insects such as leaf hoppers, spittlebugs, and psyllids. Signs your tree has ash decline include pale or yellow leaves, sparse foliage, and dying branches.
Ash decline has no cure, but you can keep your tree alive longer by watering it well and giving it occasional fertilizer.
Arizona ash is vulnerable to sunscald when planted in hot, sunny climates. This non-infectious disease causes tree bark to discolor, split, and eventually peel away, leaving the tree susceptible to insect damage.
Other Location Considerations
Arizona ash has no thorns and is non-toxic, so you can feel comfortable planting it where it might come in contact with people and pets. However, it is highly allergenic, so if anyone in your household has springtime tree allergies, this might be one tree to skip.
Arizona ash ultimately becomes a very large tree that drops its leaves in late November to December, so don’t plant it where you don’t want debris, such as near a pool or near your house where its leaves can clog your gutters (if you have any).
Arizona Ash:
The Essentials
| Common Names | Arizona ash, velvet ash |
| Scientific Name | Fraxinus velutina |
| Origin | Southwestern US |
| Plant Type | Deciduous tree |
| USDA Zones | Zones 6 – 11 |
| Cold Hardy | To -10℉ |
| Flower Color | Inconspicuous |
| Flower Season | Spring |
| Mature Size | 40’ high x 30’ wide |
| Growth Rate | Moderate |
| Sun Tolerance | Full, part sun |
| Water Needs | Moderate |
| Pests & Diseases | Root rot, ash decline, ash borers |
| Garden Friendly | No thorns, non-toxic |
| Wildlife | Attracts birds, bees, butterflies Deer, rabbit resistant |
How to Plant
The rule of thumb when planting any shrub or tree in the desert is to dig a hole three times as wide as the root ball but no deeper. Amending the soil is not recommended. Counterintuitively, backfilling with the same native soil you just dug up helps your plant develop a stronger root system.
When to Plant
The best time to plant Arizona ash is in the fall. This gives your tree three seasons to grow roots and get established before the following summer.
The second best time is in spring, the earlier the better. This still gives your plant time to get established before the intense heat of June arrives.
How to Care for Arizona Ash
Whether you’ve recently planted a new ash tree or have an existing one in your yard, here’s how to take care of it to keep it healthy and looking its best.
How to Water New Plants
Once you’ve got your ash tree in the ground, watering is your most immediate concern.
Here is the recommended watering schedule for new trees planted in the spring or fall.
| Weeks 1 & 2 | Every 3 – 4 days |
| Weeks 3 & 4 | Every 6 – 7 days |
| Weeks 5 & 6 | Every 7 – 10 days |
| Weeks 7 & 8 | Every 10 – 14 days |
After week 8, gradually extend the time between waterings.
How to Water Established Plants
As your tree becomes established, there are two watering factors to consider.
- First is how often to water. This will vary with the seasons.
- Second is how much water to give your tree with each watering. This depends on its current size.
To determine the ideal watering schedule for any desert tree, you’ll find everything you need to know, including easy-to-use charts, at How to Water Desert Trees: How Often? How Much?
Once your tree is established, it should not need supplemental water during the winter when it’s dormant.
Should You Fertilize?
In general, native trees don’t require fertilizer. However, if you notice your ash tree’s leaves are turning yellow, consider treating it with iron chelate fertilizer in the spring to prevent iron chlorosis.
How to Prune
If you’re unsure about how to shape your tree as it grows, I strongly urge you to hire a professional. Hiring an arborist (not a so-called “landscaper”) to get your tree off to the right start is an excellent investment that will result in a beautiful tree that will grace your yard for decades to come.
Note that pruning is not recommended for the first two to three years after you plant your tree. Waiting can be hard!
And be careful not to remove too much of your tree’s canopy, which could make it more susceptible to sunscald.
Arizona Ash Cultivars
There are several Arizona ash cultivars on the market. Here’s a quick look at a few of the most popular.
Fraxinus velutina ‘Fan Tex’ is considered the best variety for residential landscapes. This hybrid performs better in hot, dry conditions than the parent plant and has a longer growing season. The leaves arrive earlier in the spring and die later in the fall. It is a clone of a male plant and so will produce no seeds. It’s also known as Fraxinus velutina ‘Rio Grande’.
Fraxinus velutina ‘Modesto’ is another seedless male clone. It’s fast-growing, quickly providing shade with lime green leaves. It tends to be somewhat smaller than the parent plant.
Fraxinus velutina ‘Bonita’ is another male seedless variety that is somewhat smaller yet. It is drought-tolerant and a fast grower with strong wood, making it a good choice to withstand high winds. (Wind is a rarely considered factor, but I have lost several plants, including trees, to wind.)
Don’t Confuse Arizona Ash With…
In Texas, there’s a tree sold as either Mexican ash or Arizona ash (Fraxinus berlandieriana), but this is not the same tree as the true Arizona ash discussed in this article. This common name is puzzling considering that Fraxinus berlandieriana is a riparian native to south Texas!
Plant Lover Facts
Arizona ash (Fraxinus velutina) goes by many common names including desert ash, leather leaf ash, and smooth ash.
But its most common alias is velvet ash. Velutina, the species name, means velvety in Latin. The undersides of the leaves are often covered with velvety hairs.
Native Americans found the branches of the Arizona ash to be suitable for tool making. They used them to make hunting bows, walking sticks, and tools for gathering saguaro cactus fruit, pinyon pine nuts, and mezcal agave.
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Author Bio
Deane Alban is the creator of Southwest Gardener. She is a science writer with a bachelor’s degree in botany from the University of South Florida. Gardening is her lifelong passion. She’s been gardening in Tucson for 15 years.
