Washingtonia robusta


Washingtonia robusta, known by common name as the Mexican fan palm, Mexican washingtonia, or skyduster is a palm tree native to the Baja California peninsula and a small part of Sonora in northwestern Mexico. Despite its limited native distribution, W. robusta is one of the most widely cultivated subtropical palms in the world. It is naturalized across the southern United States, Mediterranean, and Middle East.

Description

W. robusta grows to tall, rarely up to. The leaves have a petiole up to long, and a palmate fan of leaflets up to long. The petioles are armed with sharp thorns. The inflorescence is up to long, with numerous small, pale orange-pink flowers. The fruit is a spherical, blue-black drupe, diameter; it is edible, though thin-fleshed.

Taxonomy

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.

Nomenclature

  • English: Mexican fan palm, Mexican washingtonia, skyduster
  • Spanish: abanico, ''palma colorado, palma real, palma blanca, palma negra
  • Seri: Zamij ctam''

    Distribution

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. 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 fewest plants in the palm oases that are shared with two other more numerous species, Brahea brandegeei and Sabal uresana.

Cultivation

Like the closely related Washingtonia filifera, it is grown as an ornamental tree. Although very similar, the Mexican washingtonia has a narrower trunk, and grows slightly faster and taller; it is also somewhat less cold hardy than the California fan palm, hardy to about.
Field research conducted on W. robusta in its native habitat on the Baja California peninsula concluded that its potential longevity may exceed 500 years. 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." 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 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.

Maintenance

Like the related W. filifera, W. robusta does not drop its older leaves but retains them firmly attached to the trunk as it grows. This is referred to as the beard or skirt of the tree. When growing in the wild, the tree's large, heavy skirt is a great asset for wasps, rats, mice, scorpions, birds, spiders, and other small animals, who can use the complex environment as a nest and habitat similar to the way small fish and invertebrates nest in a coral reef. However, in the context of a hotel, golf course or home, the proliferation of small animals can become a nuisance to human property owners. For this reason, when W. robusta is cultivated, its skirt of heavy, dry, dead leaves is typically cut, and then the leaf bases are removed to give the trunk a relatively smooth, uniform appearance by arborists. Due to the tree's great height, and the extreme weight of the skirt, this process has been extremely dangerous and potentially lethal to arborists. As a result, the California Department of Public Health developed a series of reports and training materials to prevent accidents while trimming tall skirt-bearing palms such as W. robusta.