| Washingtonia filifera | |
|---|---|
| Washingtonia filifera in native grove near Twentynine Palms, California. | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Monocots |
| (unranked): | Commelinids |
| Order: | Arecales |
| Family: | Arecaceae |
| Genus: | Washingtonia |
| Species: | W. filifera |
| Binomial name | |
| Washingtonia filifera (Lindl.) H.Wendl. |
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Washingtonia filifera (filifera - Latin "thread-bearing"), with the common names California Fan Palm [1], Desert Fan Palm, Cotton palm, and Arizona Fan Palm. It is a palm native to southwestern North America between an elevation range of 100–1,200 metres (330–3,900 ft), at seeps, desert bajadas, and springs where underground water is continuously available. [2]
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Washingtonia filifera is the only palm native to the Western United States, including Texas, and 'palm iconic' California. [3][4] [5] It is the largest native palm in the contiguous United States. The primary populations are found in desert riparian habitats at spring fed oases in the Colorado Desert (Low Desert) of Southern California; with important isolated populations in the Sonoran Desert along the Gila River in Yuma and Yavapai counties in Arizona, and in northern Baja California of Mexico. [2] [6] It has locally naturalized in the Mojave Desert at warm springs near Death Valley and southern Clark County, Nevada, in extreme northwest Sonora Mexico, and also in Florida and the U.S. Virgin Islands. [2][7] As an ornamental tree it is cultivated in suitable temperate climates worldwide.
The Washingtonia filifera palm grows to 18 metres (59 ft) in height (occasionally to 25 metres (82 ft)) in ideal moisture and microclimate conditions. "
The leaf fronds are up to 6 feet (1.8 m) long, made up of a petiole up to 2 metres (6.6 ft) long, bearing a fan of leaflets 1.5–2 metres (4.9–6.6 ft) long. They have long thread-like white fibers, filifera-filaments, between the segments. When the fronds die they remain attached and drop down to cloak the trunk in a wide skirt. The shelter that the skirt creates provides a microhabitat for many small birds and invertebrates.
Washingtonia filifera can live from 80 to 250 years or more. The genus name honors George Washington, the first President of the United States. The plant is popularly honored by its common name and habitat used in naming communities and landforms, such as Palm Springs, California.
Fan palms provide a habitat for Desert Bighorn Sheep and the California endemic Peninsular Bighorn Sheep, Hooded Oriole, Gambel's Quail, Coyotes, and a rare bat species (Lasiurus xanthinus) that is especially fond of W. filifera groves. Hooded Orioles rely on the trees for food and places to build nests. Both Hooded Orioles and coyotes play an integral part in seed distribution.
Joshua Tree National Park preserves and protects healthy riparian palm habitat examples in the Little San Bernardino Mountains section, and westward where water surfaces up through the San Andreas Fault on the east valley side. In the central Coachella Valley the Indio Hills Palms State Reserve and nearby Coachella Valley Preserve a large oasis is protected and accessible. In the Santa Rosa Mountains on the west side of the valley, at 'Palm Canyon' in the Santa Rosa and San Jacinto Mountains National Monument, and in Anza-Borrego Desert State Park, both parks have large and diverse Washingtonia filifera canyon oases habitats.
The palm boring beetle Dinapate wrightii (Bostrichidae) can chew through the trunks of the trees. Eventually a continued infestation of beetles can kill various genera and species of palms, including this one. The recent discovery of the red palm weevil (Rhynchophorus ferrugineus) in Southern California may pose a threat to many palms, with coastal garden Washingtonia filifera trees already a known host.[8]
Today due to urbanization and ground water depletion, palm oases are retracting and disappearing. Increased agriculture irrigation needs of well water has lowered aquifers which decreases or stops water availability at seeps and springs in palm oases. This creates a threat not only to the only native palm of the western United States, but also all the organisms which rely on the riparian palm oases habitat to survive.
Fossils of this palm are known to exist as far north as Colorado, Wyoming and Oregon. The palm apparently reached its current form by at least 50 - 70 million years BP.
Natural oases environments are mainly restricted historically to the area surrounding warm or hot springs, near the source, or shortly downstream from the source.
Grazing animals including deer and cattle and in more ancient times, Giant Sloths and other extinct herbivores, can kill young plants through trampling, or by eating the terminus at the apical meristem, which is the growing portion of the plant. This may have kept these palms restricted to a lesser range than would have been expected if one simply considers the availability of water sources.
Typically, the oasis environment found today is one which may have been protected from colder climatic changes over the course of its evolution. Thus this palm is restricted by both water and climate to widely separated relict groves. The trees in these groves show little if any genetic differentiation, which suggests that this species is genetically very stable.
The fruit of the fan palm was used by Native Americans. It was eaten raw, cooked, or ground into flour for cakes. The Cahuilla tribe used the leaves to make sandals, thatch roofs, and for making baskets. The fan palm was a valuable resource and the stems were used to make utensils for cooking. The Moapa band of Paiutes as well as other Southern Paiutes have stated memories of grandparents also using this palm's seed, fruit or leaves for various things. [9] [10] The Southern Paiutes are related linguistically and by ancient trade routes to the Cahuilla.
Washingtonia filifera is widely cultivated as an ornamental tree. It is one of the hardiest of Coryphoidiae palms, is tolerant of considerable frost, and is rated as hardy to USDA hardiness zone 8. It will survive temperatures of −10 °C (14 °F) with minor damage, and established plants have survived, with severe damage to the foliage, brief periods of temperatures as low as −12 °C (10 °F). It is a favorite of cold-hardy palm enthusiasts. The plants grow best in warm temperate climate with dry summers and wetter winters. Specimens outside of Mediterranean climates do not grow as large, rarely exceeding 15 metres (49 ft). It is often seen in California with the closely related species Mexican Fan Palm (Washingtonia robusta) - a less hardy palm needing slightly milder winters, that may be visibly damaged at −7 °C (19 °F) and is more amenable to humidity making it more favored along the Gulf Coast. [11]
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