Washingtonia robusta

W. robusta grows to 25 m (82 ft) tall, rarely up to 30 m (98 ft). The leaves have a petiole up to 1 m (3 ft 3 in) long, and a palmate fan of leaflets up to 1 metre (3 ft 3 in) long. The petioles are armed with sharp thorns. The inflorescence is up to 3 m (10 ft) long, with numerous small, pale orange-pink flowers. The fruit is a spherical, blue-black drupe, 6–8 mm (1⁄4–5⁄16 in) diameter; it is edible, though thin-fleshed.[6]

It is one of two species in the genus Washingtonia. The other is the close relative Washingtonia filifera, which occupies a more northerly distribution. Compared with W. robusta, W. filifera has a thicker trunk and dull green leaves.[7]

This palm is native to the Baja California peninsula and Sonora. On the peninsula, it occurs from the Sierra de La Asamblea and the Baja California desert south into the Vizcaino region and the Sierra de La Giganta, and into the southern cape.[8] In Sonora, it occurs in canyons in the western half of the state, particularly in the palm oases of the Sierra El Aguaje north of Guaymas. It is relatively restricted, and is suspected to be a relict population in Sonora. It has the least number of plants in the palm oases that are shared with two other more numerous species, Brahea brandegeei and Sabal uresana.[7]

The approximate range of cultivation of Mexican fan palms in the US with little to no winter protection

Like the closely related Washingtonia filifera (California fan palm), it is grown as an ornamental tree. Although very similar, the Mexican washingtonia has a narrower trunk (which is typically somewhat wider at the base), and grows slightly faster and taller; it is also somewhat less cold hardy than the California fan palm, hardy to about −8 °C (18 °F).

Field research conducted on W. robusta in its native habitat on the Baja California peninsula concluded that its potential longevity may exceed 500 years.[9]

Supporting research by Barry Tomlinson and Brett Huggett states that there is "evidence for extreme longevity of metabolically functioning cells of considerable diversity in palm stems."[10] Many of the iconic "sky dusters" of Los Angeles that have survived the chainsaws of progress are documented in photography from the 19th century.

The Mexican fan palm is normally grown in the desert Southwestern United States, in areas such as California, Arizona, southern Nevada, extreme southwestern Utah and Texas. It also cultivated in the coastal areas of South Atlantic states and the Gulf Coast, including extreme southern North Carolina, coastal South Carolina, southern Georgia, and Florida. Along the Gulf Coast, Mexican fan palms can be found growing along the Florida west coast westward to South Texas.

Washingtonia × filibusta is a hybrid of W. robusta and W. filifera, and has intermediate characteristics of the two parents, especially greater tolerance of wet cold.[11]

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  Flowering palm in Chandler, Arizona
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  Infructescence
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  Inflorescence
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  Arizona State University's Palm Walk
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  Species in Venice Beach, California
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  W. robusta growing in Saint Simons Island, Georgia
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  W. robusta and Canary Island date palms are commonly seen lining many streets throughout San Jose, California.
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  Palm trees lined up at S. Occidental Blvd between Koreatown and Westlake of Los Angeles, California
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  Species line Santa Clara Street in San Jose, California
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  Oldest palms in Los Angeles, planted circa 1875
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  A Mexican fan palm tree in Enterprise, Alabama

• Flora of North America Vol. 22 Page 106 Mexican fan palm, palmier évantail du Mexique Washingtonia robusta H. Wendland, Garten-Zeitum (Berlin). 2: 198. 1883.
• Scanpalm - Washingtonia robusta