Washingtonia filifera
California fan palm, Washingtonia filifera, is the perfect accent plant for arid gardens, endowed with all the appealing traits we love about native species.
From wildlife value and climate resilience to fire resistance, this species has got the good stuff in spades.
With its towering trunk, dense crown of pleated fronds, and threadlike filaments, the California fan palm is both distinctive and surprisingly low maintenance.
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It supports a wide range of wildlife and offers an important connection to the cultural and ecological history of the southwestern US.
Indigenous groups relied on this species for food, tools, and shelter, and remnant stands remain ecologically and archaeologically significant today.
In our guide to growing fan palms we provide an overview of the species typically referred to by this common name.
Read on to learn more about growing California fan palm, a long and leggy native of the western United States.
What You’ll Learn
A member of the palm family, Aracaceae, this species is the only palm native to the western United States.
It’s also commonly known as the Arizona or desert fan palm, and American cotton or petticoat palm.
Ranging from Baja California to southern California, east through the Mojave Desert, and into Arizona, W. filifera is found growing wild in oases, seeps, and stream edges.
Widely grown in arid and semi-arid regions around the world, California fan palm has naturalized in other locations such as the warm springs area near Death Valley, California.
Growing up to 59 feet tall and occasionally, under optimal conditions, as tall as 82 feet, this enormous species has a thick, columnar trunk often covered by a shag of dead leaves.
The large leaves sit at the apex of the trunk, crowning the tree with gray-green foliage.
Leaves can grow up to five feet long, are deeply pleated, and sport small, white filaments along each leaf segment’s margin, giving the species its latin name “filifera.”
In summer, profusions of creamy yellow and white blossoms are produced from the center of the crown. The individual blossoms are small and tubular in shape.
Quick Look
Common name(s): California, Arizona, or desert fan palm, petticoat palm
Plant type: Evergreen monocotyledonous perennial
Hardiness (USDA Zone): 8-11
Native to: Southwestern United States, Baja California
Bloom time / season: Summer
Exposure: Full sun
Soil type: Loose, well draining
Soil pH: 6.0-8.0, slightly acidic to alkaline
Time to maturity: 19 years
Mature size: 60-82 feet tall, up to 20 feet wide
Best uses: Accent plant, desert landscapes, wildlife gardens, large-scale plantings
Taxonomy
Order: Arecales
Family: Arecaceae
Genus: Washingtonia
Species: Filifera
After pollination, which is typically performed by insects, clusters of single-seeded black drupes ripen into fall.
Hardy in USDA Zones 8 to 11, W. filifera likes it hot. In its native desert climes, summer temperatures often climb to over 100℉. However, although rainfall is not necessarily bountiful, this species is a sure fire indicator of the presence of water.
The native people that once occupied its native range settled amongst groves of California fan palms as an assurance that they too could find the hydration they needed.
True to its sunbaked roots, W. filifera
appreciates hot, dusty soils. Although this species is found in nutrient-poor substrates in the wild, it does remarkably well in a wide range of soil types and, like most plants, loves an occasional dose of fertilizer.
Historically, the Cahuila and Kami people utilized W. filifera in numerous important ways.
The fruits, similar in taste and appearance to dates, were dried and eaten, as were young buds and flowers. Sandals, baskets, and thatching for roofs were made from leaf fibers, and hunting bows were made from the tough, woody petioles.
Natural California fan palm oases are considered important archeological sites as a result of their close association with these people.
How to Grow
Although W. filifera naturally occupies just a small corner of North America, this species is actually fairly adaptable.
It prefers a hot, arid environment and is hardy in Zones 8 to 11.
Though it’s accustomed to scorching summers in its native range, with temperatures above 100°F, it can tolerate brief cold snaps down to about 13°F.
That said, temperatures that linger below freezing can cause tissue damage, particularly to young plants or those in exposed areas.
If you’re gardening in Zone 8, it’s wise to plant near a south-facing wall or other thermal mass to take advantage of reflected heat.
Protecting the plant from winter winds can also help reduce stress when the mercury drops.
Light
This species performs best in full sun, ideally six or more hours of direct light daily.
While it will tolerate partial shade, growth slows and fronds can become elongated and sparse.
Soil
In the wild, W. filifera thrives in coarse, well-draining soils that are often alkaline and nutrient-poor.
But it’s not particularly fussy in cultivation. It will tolerate a wide range of soil conditions so long as drainage is excellent.
Sandy, gravelly, or rocky substrates are ideal. Avoid heavy clay or any site that retains moisture, as the plants will not tolerate soggy roots.
As with most desert dwellers, an excess of water is the number one enemy.
Water
In the wild this species is found near seeps, rivers, and oases.
If your area experiences little to no rainfall over the course of a week or two, make sure to water deeply, paying particular attention to young specimens.
I like to turn the hose on to a trickle and leave it at the base of the trunk for a few hours.
Once established, this species is drought-tolerant but will appreciate water during extended dry spells.
Fertilizing
Although these tenacious plants live in nutrient poor soils in their natural habitat, they do very well if fed throughout the growing season.
I personally prefer to top dress my plants with several inches of compost around the trunk.
However, a slow-release fertilizer formulated for palm trees will do the trick too.
If you need a recommendation, I use Jobe’s Organics granular fertilizer. It has an NPK ratio of 4-2-4 which is ideal for palms.
Jobe’s Organics Palm Fertilizer
This product is available from Jobe’s Organics via Amazon.
Follow the application instructions on the package and make sure to water after fertilizing so the nutrients reach the roots.
Where to Buy
You can generally find California fan palms available in nurseries in their native range.
In other regions, you may need to go to a retailer that has a good selection of palms or desert-adapted plants.
When shopping, make sure you select the correct species rather than the Mexican fan palm, W. robusta.
Maintenance
When W. filifera is established, there’s very little to do to keep it thriving.
Pruning is not necessary unless you dislike the gorgeous, textured shaggy skirt of dead leaves.
Keep in mind, these leaves provide habitat to many creatures, such as tree frogs, rat snakes, and numerous birds.
If you live in a fire-prone area, it may be a relief to know that California fan palm is moderately fire resistant.
However, the dead fronds are highly flammable. If keeping this kind of natural fuel close to the house concerns you, use a pair of sharp, clean pruners to snip away dead leaves at the base of the petioles every year.
Propagation
The easiest way to get started is to purchase a bare root or potted plant from the nursery for transplanting. If you’re a bit more patient, you can also propagate this species from seed.
From Seed
Seeds can be purchased or collected from ripe fruit if you live in an area where these plants grow natively.
When ready, the fruit turns jet black, which typically happens by late autumn or early winter.
Soak the small, black drupes in warm water for three to four days to loosen the pulp and speed up germination. Setting the container on a heat mat will help maintain a consistent temperature.
After soaking, remove the outer rind using the rough side of a sponge or fine sandpaper. Fill several four-inch pots with moistened, well-draining potting mix formulated for palms.
Sow one seed in each pot just below the surface of the soil. Keep the soil moist, but not soaking.
Move your pots somewhere with lots of sunshine and consistently warm temperatures. Using a heat mat set to 80℉ will help encourage germination.
The seeds should sprout within a few weeks. At this point you can ease up on watering and allow the surface of the soil to dry out between applications.
When seedlings reach six inches tall, transplant them into six-inch containers using the same soil mix. Once they’re large enough to withstand competition from weeds, they can be hardened off and planted out in the garden.
Transplanting
If you’ve purchased a plant from the nursery or your seedlings are ready, dig a hole the same depth and width as the container the plant is currently growing in.
Remove the specimen carefully from its pot, set it into the hole and backfill to fill in any gaps. Tamp the soil down before watering in well.
While your California fan palm is small, make sure to protect it from nibbling herbivores such as deer and rabbits.
If your young plant loses the top of its crown part to a hungry herbivore, it won’t recover.
Constructing a loose cage of chicken wire around the plant until it reaches about five feet tall should provide adequate protection.
Pests and Disease
When sited correctly, in the hot, sunny conditions they love, California fan palms are a delight to grow and care for. There are, however, a few worrisome conditions to keep an eye out for.
Pests
Many beneficial insects will use the flowers, fruits, and foliage of California fan palm for food and cover.
There are two insects that can be very destructive:
Red Palm Weevil
Red weevils (Rhynchophorus ferrugineus) are large black and red insects measuring up to one and a half inches long.
These invasive insects from tropical Asia have spread throughout the world and they tunnel into trunks and crowns, causing rot, wilting, and collapse.
The larvae are pale yellow with brown heads and can reach up to two inches in length.
Fortunately W. filifera has demonstrated some resistance to these pests. If you discover piles of insect frass at the base of the plant, inspect the trunk for tunnels and the foliage for adult weevils.
Be sure to report this invasive pest to your local extension agent if you find it as efforts are underway to eradicate red palm weevils from anywhere outside their native range in Asia.
Trunk injections of systemic insecticides are the best way to control these pests but applications can only be administered by a professional.
Palm Leaf Skeletonizer
A small, silvery brown, unremarkable looking moth, the palm leaf skeletonizer (Homaledra sabalella) can cause trouble for California fan palms.
Native to the southern United States, this night-flying insect lays eggs on the foliage. The transparent larvae that hatch create silken webs and feed on the softer foliage between the veins, skeletonizing the leaves.
Although these pests can create unsightly damage to California fan palms, it is primarily a cosmetic problem.
In years with high numbers of larvae, infested foliage can be pruned out and burned, or sprayed with a high pressure hose. Most insecticides are ineffective as the larvae are protected by their silken webbing.
Disease
An excess of moisture spells doom for many types of fan palms.
Most of the diseases that are really troublesome for this species are the result of overwatering or excess humidity. When sited properly in hot, dry, sunny conditions, these issues are rare.
Bud Rot
The black lesions caused by bud rot are the work of insidious water molds in the Phytophthora genus.
This pathogen enters through wounds in plant tissue, often after heavy, prolonged rainfall and causes the crown to turn soft and mushy.
Early signs include drooping, yellowing, or prematurely dropping leaves.
Unfortunately, there is no cure for bud rot. Affected trees must be cut down and discarded to limit the spread.
Butt Rot
Caused by the soilborne fungus, Ganoderma zonatum, butt rot causes soft brown spots on the trunks of infected trees.
As the disease progresses, the crown may start to rot, causing wilting, yellowing foliage. Eventually, mushrooms may appear at the base followed by trunk rot.
There is no effective treatment so you’ll have to remove and discard affected specimens and avoid planting any type of fan palm in the same location, as the fungus persists in the soil.
An Agreeable All-Rounder
Fire-resistant, drought-tolerant, cold-hardy, and supportive of local wildlife, California fan palm is a standout choice for sunny, arid landscapes.
With its towering height, long lifespan, and crown of finely divided fronds, it brings both beauty and ecological value to the garden.
If you’re interested in adding plants to your garden that can handle the stresses of a changing climate while offering food and shelter for wildlife, this species fits the bill.
Do you grow California fan palm? Have you ever seen it growing in the wild? Please let us know in the comments section below!
And for more information about growing palms, check out these guides next:
We’ve raised these beautiful Washingtonia filifera for 13 years. The builder planted numerous Mexican fan palms in our development, but as our California fan palms matured, neighbors asked what type of Palm we were growing. Now I see them being grown throughout our neighborhood. We’re currently raising about 35 seedlings to share with more neighbors. They are a beautiful, minimal maintenance tree here in Palm Springs.
Thanks for sharing, Gloria! Those are beautiful, healthy trees!