Washingtonia filifera

Washingtonia filifera
Washingtonia filifera growing wild near Twentynine Palms, California
Conservation status
Near Threatened (IUCN 2.3)
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.

Washingtonia filifera (filifera - Latin "thread-bearing"), common names Desert Fan Palm, American Cotton palm, Arizona Fan Palm, or California Fan Palm) is a palm native to the desert oases of Central, southern and southwestern Arizona, southern Nevada, extreme northwest Mexico and the inland deserts of Southern California.

This palm grows up to 23 m (exceptionally 30 m) in good growing conditions. It is the only palm native to the contiguous United States west of the Balcones Fault Zone in Texas^[1] (except for isolated stands of Sabal minor in the Texas Hill Country [ Clover, E. U., 1937. Vegetational survey of the lower Rio Grande valley, Texas. Madrono 4:41-72 ].

The leaves have a petiole up to 2 m long, bearing a fan of leaflets 1.5-2 m long, with white, thread-like fibers between the segments. When the leaves die they bend downwards and form a skirt around the trunk. The shelter that the skirt creates provides a microhabitat for many 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.

Ecology

Fan palms provide a habitat for Bighorn Sheep, Hooded Oriole, Gambel's Quail, Coyotes, and the palm boring beetle Dinapate wrightii (Coleoptera: Bostrichidae), and a rare bat species, Lasiurus xanthinus 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.

Dinapate beetles can be problematic and chew through the trunks of the trees. Eventually a continued infestation of beetles can kill a palm, opening up space for a new palm to grow.

Today due to urbanization, palm oases are disappearing. Increased agriculture has lowered ground water supplies which decreases the amount of water available in palm oases. This creates a threat not only to the far western United State's only native palm, but also all the organisms which rely on these trees in order 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.

Cultivation and uses

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. It should be noted that The Southern Paiutes are related linguistically and by ancient trade routes to the Cahuilla.

It is widely cultivated as an ornamental tree. (It is not as widely cultivated as the Mexican Fan Palm Washingtonia robusta - a close cousin which is grown throughout the lower elevations of Nevada, California, Arizona, Texas, New Mexico and extreme southwestern Utah. W. filifera is one of the hardiest of Coryphoidiae palms, and repeatedly survives dips into the teens and even several inches of snow, making it a favorite of cold-hardy palm enthusiasts.

The less hardy cousin W. robusta needs slightly milder winters and may be visibly damaged at 20 degrees Fahrenheit and is also more amenable to humidity making it more favored along the Gulf Coast, in states such as Texas, Louisiana, and Florida, and the Mediterranean region. It is widely grown in interior Texas, as it is sufficiently hardy in such places as San Antonio, Austin, Midland, Odessa, and El Paso.^[2]

The plants grow best in warm temperate climate with dry winters and wetter summers. Specimens outside of Mediterranean climates do not grow as large, rarely exceeding 15 m. The plants are tolerant of considerable frost and the species is rated as hardy to USDA zone 8; it will survive temperatures of -10 °C with minor damage, and established plants have survived brief periods of temperatures as low as -12 °C but with severe damage to the foliage.

^[3]

Gallery

Washingtonia filifera used in landscaping, St. George, Utah.

Fibrous threads on leaf segments, especially pronounced in Washingtonia filifera.

Notes

References and external links

Wikimedia Commons has media related to: Washingtonia filifera

• Johnson (1998). Washingtonia filifera. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006.
• Washingtonia filifera at Floridata
• C. Michael Hogan. 2009. California Fan Palm: Washingtonia filifera, GlobalTwitcher.com, ed. Nicklas Stromberg
• Washingtonia filifera in Flora of North America
• Scanpalm - Washingtonia filifera
• http://www.nps.gov/jotr/nature/features/oases/oases.html
• http://www.xeri.com/Moapa/wf-hr-part1.htm
• http://www.livingdesert.org/plants/california_fan_palm.asp
• http://www.xeri.com/Moapa/wf-hr-foreword.htm