Desert Willow (Chilopsis linearis)

The desert willow is a little tree that adds color and fragrance to your backyard, provides summer shade, and attracts birds, hummingbirds, and bees. The long, slender leaves make you think of willow, but once you learn some desert willow tree facts, you’ll see that it is not in the willow family at all.

I. Appearance and Characteristics 

Chilopsis is a monotypic genus of flowering plants containing the single species Chilopsis linearis. It is known commonly as desert willow or desert-willow because of its willow-like leaves, but it is not a true willow – being instead a member of the catalpa family.

It is a shrub or tree native to the southwestern United States and Mexico. It is commonly seen in washes and along riverbanks.

Ranging from 1.5 to as much as 8 meters in height, it can take the form of a shrub or small tree. The linear, curved, deciduous leaves are 10 to 26 cm long and just a few millimeters wide.

The generic name is derived from the Greek words χεῖλος, (cheilos), meaning “lip,” and ὄψις (opsis), meaning “resembling,” referring to the flowers. They occur in a terminal panicle or raceme, blooming in May through September. About two to four flowers at a time are open in each inflorescence. The calyx is about 8–14 mm, slightly inflated, and varying shades of purple, while the corolla is 2–5 cm, and with colors ranging from lavender to light pink. The throat and lower lip has a pattern of yellow ridges and purple lines, and the margins are crinkled. It is pollinated primarily by large bees in the family Apidae, such as carpenter bees, bumblebees, Anthophora, and Centris. The flowers are popular with hummingbirds as well. The fruit is a linear pod up to 35 cm (14 in) long, containing numerous winged seeds.

There are two subspecies:

• Chilopsis linearis subsp. linearis. Utah, Arizona, New Mexico, western Texas, Mexico.
• Chilopsis linearis subsp. arcuata. Nevada, California, Baja California.

Chilopsis linearis is cultivated for its large, showy flowers, and tolerance of hot, dry climates. Although the natural growth is a very irregular shape, it can be readily pruned into a conventional tree shape. A number of cultivars have been selected. Some, such as ‘Rio Salado’, have dark purple or magenta flowers.

Chilopsis may survive temperatures as low as 10 degrees F (-12 °C).

Chilopsis is closely related to the genus Catalpa and hybrids can be made between the two genera. The nothogeneric hybrid between Chilopsis linearis and Catalpa bignonioides has been named × Chitalpa tashkentensis. It originated in a botanic garden at Tashkent in Uzbekistan.

II. How to Grow and Care

Sunlight

The desert willow’s natural habitat gets plenty of sunlight, so it naturally loves its rays and thrives in nothing less than full sun. To get the best bloom production, ensure that you place it in an area that receives a full six hours of direct sunlight per day. You will notice a marked lack of blooms in shady conditions.

Temperature and Humidity

As this desert shrub does best in hot, dry regions, it will do better in microclimates that mimic those conditions in your landscape even if your yard doesn’t exactly fit that bill. Consider mimicking these conditions with the use of pavers, stone, boulders, and soilless growing medium. Areas north of USDA region seven will have a tough time with desert willows, but if you are set on giving it a try, some hardier cultivars are available. 

Watering

Once established, the desert willow can readily tolerate dry conditions and droughts with ease. It will look as if it is suffering then rebound after the next storm or watering. Watering then is advised times per month, but if it’s a particularly rough period and watering is restricted, your desert willow can make it through. This shrub is a great selection for xeriscaping.

Soil

It grows almost effortlessly in dry- to medium-moisture soil that is well-draining with a slightly higher pH; you can test your pH at home and amend the soil as necessary. When your desert willow establishes itself, it will become even more adaptable and tolerate a wider range of soil conditions, particularly when it comes to soil moisture.

Fertilizing

Desert willow is one plant that you should not fertilize. Often when it comes to fertilizer, the advice is something like, “it’s not needed, but you can if you want”—this is not one of those situations. Giving your desert willow fertilizer may sound like a great idea to boost bloom production, but what will happen is it will increase vigor and speed up the growth of the limbs. Supplemental feeding on this shrub creates soft, brittle wood that is susceptible to breakage, especially with strong winds.

Pruning

Pruning your desert willow is a matter of keeping it tidy and cutting off dead growth to stimulate new growth. Leaving it unkempt is a possibility as well and would be much appreciated by wildlife, especially small mammals and birds who use it for shelter. The choice is all about the shrub’s intended function and your desired aesthetic.

Propagation

You can propagate desert willows by cuttings or seeds.

Propagating Desert Willow by Seed

Propagating desert willow by seed is the preferred and easiest method. It will take some time until you have seedlings ready for hardening off but it just takes a few steps. Here’s how:

• Soak your seeds in a glass containing a solution of 1/2 water and 1/2 vinegar for four hours.
• Prepare seed flats or pots and fill with soilless seed starting mix. A good recipe for this can be found here.
• Sow the seeds no deeper than ¼ inch in your pots or flats and moisten. Keep moist until germination.
• Transplant your seedlings to a larger pot once seedlings produce two sets of leaves and are four inches tall. This pot should be big enough to allow space to grow.
• Place outside for a month to harden up and allow it to acclimate to the outdoors. You can then plant or keep in the container to allow it to grow for the first year to plant the following year.

Propagating Desert Willow by Cuttings

While not as easy as the seed method the cutting method allows you to have plants that are already much more mature and exact clones of plants you already possess. This is great in cases of cultivars that do not produce seeds. Here’s how:

• Cut a small branch of softwood desert willow closest to a leaf node. 
• Dip your cutting in rooting hormone. Follow the instructions on your specific brand.
• Place your cutting in a jar of water and wait for roots to appear. If growth is slow, add rooting hormone to the water.
• Transfer into a pot of soilless potting mixture once roots have developed and there are three to five roots. Let it grow from here.
• Water the plant frequently and keep soil well-drained. After two-three months your plant should have established a healthy root system that will be able to survive planting.

How to Grow From Seed

Desert willow seeds will lose their viability quickly, so it’s best to get them in soil while their fresh to give them the best chance at success.

• Soak the seeds in a bit of water for a few hours prior to sowing to help the process along.
• Plant them about 1/4 inch deep in garden flats or pots.
• Keep the soil moist until germination occurs hopefully in between one to three weeks.
• Transfer to one-gallon pots full of potting mix once you see a set or two of leaves.
• Place the pots in direct sunlight until the spring season when the conditions are right for them to be moved to the ground.

Pests and Diseases

Common Pests and Plant Diseases

One of the truly wonderful things about the desert willow is that it is not particularly susceptible to many diseases or pests. Any ailments it does suffer from are not serious and will most likely not threaten the life of your shrub. The worst Insects that bother your shrub will be aphids, and they can easily be guarded against with a good burst of a hose. You will want to consider pesticide use carefully around the desert willow due to its importance as a source of food for pollinators and wildlife.

Common Problems 

The hardiness of this shrub results in very few problems. If a desert willow is struggling it’s normally related to watering issues.

Wilting and Yellowing Leaves

This is a telltale sign that the shrub is receiving too much water. The soil should be dry to the touch and not holding water. This can lead quickly to root rot, so check for softening or darkening of the roots and any unpleasant odors. Allow the plant to dry completely before irrigating again and add compost around the roots to increase drainage going forward.

III. Uses and Benefits 

• Ornamental uses

An attractor of bees and hummingbirds, desert willow is a good choice for a specimen shade tree or as an ornamental in a smaller garden. Planted in a row, they make a tall, pretty screen, or they can be pruned annually as a hedgerow, which provides more significant quantities of flowers. This tree combines well with Agave, Aloe, or Prickly pear.

• Medicinal uses

Parts of the plant have been used in traditional medicine. It has been used to treat fungal infections such as candidiasis and athlete’s foot, as well as wounds and coughs.

• Other uses

The wood was used to make bows and baskets.