What Is Desert willow?
The desert willow (Chilopsis linearis), also known as the Arizona rosewood, is a small tree or large shrub that belongs to the botanical family Bignoniaceae. There are about 80 species of Chilopsis in tropical and subtropical regions worldwide, including South America and Australia.
The desert willow was introduced to the U.S. by Spanish missionaries in the 1700s, and it was used extensively on mission properties in California, Arizona, Texas, and New Mexico as a decorative landscape plant. Today the desert willow is widely cultivated in areas of warm climates.
Care & Maintenance
Desert willow care is relatively easy. The plant thrives in most well-drained soils, including clay. It prefers full sun but can also tolerate partial shade, and it requires little supplemental water once established.
However, desert willow is very slow growing (3 to 6 inches per year), so be prepared for a long wait before you see any significant growth from your plant.
This tree or shrub grows up to 18 feet tall when mature, but it’s often pruned as a smaller ornamental hedge or screen. Desert willow trees are relatively tolerant of drought conditions and grow quickly when watered regularly during their first few years of growth; however, if they’re grown in areas with moist winter weather (Upper South, Gulf Coast), they may develop winter burn.
Desert willow trees are relatively pest-free but can be scratched or stained by rodents such as deer or rabbits.
Deer also enjoy eating the seedpods of desert willow shrubs and trees. In some areas, this plant is considered a noxious weed, because it grows so easily and can quickly crowd out native plants in an area.
The plant has become naturalized in parts of the Southwest, and its range continues to expand.
It’s a common landscape ornamental throughout southern Arizona (where it was first introduced) as well as Texas, New Mexico, California, and southern Nevada. It’s hardy from USDA plant hardiness zones 5 through 9—perhaps as low as zone 4 in the colder parts of its growing range.
Light Requirements
The desert willow is a slow-growing, shade-tolerant tree or shrub. It prefers full sun but can also grow in partial shade.
Water Requirements
Desert willow can tolerate drought conditions once it’s established. However, for the first three or four years, you water your desert willow frequently. Deep watering is best because it encourages extensive root growth and prevents surface drying that can lead to powdery mildew problems. The more drought-resistant a plant’s roots are, the less likely it is to display foliar disease problems in times of stress (such as during droughts).
Soil Requirements
The desert willow grows best in well-drained soils with a pH between 6.0 and 7.0; it tolerates mildly alkaline soils such as those found in parts of California’s Central Valley. If your soil is naturally acidic (particularly if it’s sandy soil), make sure you add some lime to the planting hole to help the desert willow grow well.
Salt Tolerance
Desert willow is moderately salt-tolerant (about 4 dS/m or 1.8 dS/m in its native habitat). It can withstand occasional flooding but otherwise prefers well-drained soils that have good aeration and drainage.
But because desert willow branches are shallow, they’re prone to drying out more quickly than deep-rooted trees, so avoid using this plant on sites where irrigation water runs off rapidly—or else install and maintain an adequate drain system. If your climate has frequent cold winters, consider growing the tree as a smaller multi-stemmed shrub or hedge with a U-shaped form.
Propagation of the Desert Willow
The desert willow is relatively easy to propagate from cuttings taken in spring, and it also grows readily from seed. Be sure to allow the seeds to dry thoroughly before attempting to plant them—otherwise, they’ll rot in the ground.
If you’re going to store your seeds for more than several months, store them in sealed containers at room temperature. If you’re storing them for less than that time period, place your seeds between moist paper towels (or another suitable medium) in resealable plastic bags.
Once you’ve germinated your seeds, transplant the seedlings immediately into small pots. After planting check soil moisture daily until new seedlings are well established.
Temperature and Humidity Requirements
Desert willow is a very easy plant to grow indoors. It requires very little water or maintenance once established—in fact, it’ll slowly die if you overwater it during the winter.
The Desert Willow trees prefer cold temperatures between 45 and 55 degrees Fahrenheit but can survive temperatures as low as minus 30 F for brief periods of time. Soil should be kept moist during winter months – just barely damp, allowing the soil to dry before watering again (a few weeks).
In areas with warm winters, avoid planting your desert willow in spring because this may lead to fast growth that burns the leaves; early fall is best for planting desert willow trees in warmer regions.
Fertilizing Requirements
Desert willow requires very little fertilizer, but if you choose to fertilize it, use a balanced (20-20-20) or high phosphorus (10-30-10), low nitrogen (0.7%) material in early spring just before new growth starts.
During times of active growth, apply a second application after six weeks and a third application three months later – this is all the fertilizer most desert willows need for full establishment. These applications are sufficient for young trees (2 years old and younger). If you have an older desert willow that’s grown several feet tall, it might require fertilizer more frequently during the growing season; check with your local county extension agent or arborist first.
Potting and repotting Requirements
Desert willows can be grown in large ceramic pots or in shallow containers made from other materials. If you’re going to use a shallow container, however, the minimum pot size is two gallons in volume —and even that’s on the small side.
Some people like to place desert willow trees and shrubs in holes dug into garden beds—that way they get some root development into native soil and avoid having to water so frequently once the plant is established.
If your desert willow was previously planted growing in an asphalt driveway or patio, it might have extensive surface roots; if so, carefully remove as much of these roots as possible before planting your tree by hand-digging a hole for it (this keeps the roots from circling around the trunk).
Do not plant your desert willow in a hole deeper than its existing rootball and as wide or wider—make sure you don’t “root-bound” the roots. Before planting, add a couple of inches of native soil (or another growing medium) on top of the rootball.
We recommend repotting your desert willow every 1–2 years using only native soil or sand/perlite mixes with little organic matter (peat moss should not be used). This is based on a number of factors including size, age, vigor, pest presence and container quality. Larger trees may need to be transplanted more often —every 2–3 years during periods of rapid growth.
Pest Problems
We’ve found a few pests that will occasionally bother desert willows.
The most common is root mealybug, Thrips palmi. This pest can infest the twigs and branches—it causes yellowing of the foliage due to injury from the adult stage (which looks like a tiny flying insect); it also produces webbing around the trunk.
The larvae feed on the roots. Infested plants may be fed upon by insects in general and suffer from stunting, leaf drop, low vigor, or death; heavy infestation may kill seedlings. If you believe your plant has this pest, contact your local county extension office for cultural control techniques or treat with any labeled pesticide appropriate for removing scale insects.
A combination of horticultural oil and insecticides may be needed for severe infestations.
The second most common pest that we’ve found is the aphid, Sipha flava. This pest overwinters on desert willows as eggs in little bumps attached to the stem—they resemble a tiny black spot.
In spring they appear as small (less than 1/8″), greenish-colored insects feeding off of new growth. If not controlled, this pest can stunt or kill your desert willow by sucking out its juice —causing leaves to wilt and die.
If you have this aphid, treat with an insecticidal soap or any labeled pesticide appropriate for controlling plant-sucking pests like Japanese beetles and tent caterpillars.
If you have a desert willow, now you can grow it —but be sure to take good care of this plant during the summer months and you’ll enjoy watching your tree become larger each year.
