| Washingtonia robusta | |
|---|---|
 | |
| Washingtonia robusta growing wild at Las Flores, Todos Santos, Baja California Sur, Mexico | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Monocots |
| Clade: | Commelinids |
| Order: | Arecales |
| Family: | Arecaceae |
| Tribe: | Trachycarpeae |
| Genus: | Washingtonia |
| Species: | W. robusta |
| Binomial name | |
| Washingtonia robusta | |
| Synonyms[2] | |
Synonymy
| |
Washingtonia robusta, known by common name as theMexican fan palm,Mexican washingtonia, orskyduster is apalm tree native to theBaja California peninsula and a small part ofSonora in northwesternMexico. Despite its limited native distribution,W. robusta is one of the most widely cultivatedsubtropical palms in the world.[3] It is naturalized across the southernUnited States, Mediterranean, and Middle East.[4][5][citation needed]
W. robusta grows to 25 m (82 ft) tall, rarely up to 30 m (98 ft). Theleaves have apetiole up to 1 m (3 ft 3 in) long, and a palmate fan of leaflets up to 1 m (3 ft 3 in) long. The petioles are armed with sharpthorns. Theinflorescence is up to 3 m (10 ft) long, with numerous small, pale orange-pinkflowers. Thefruit is a spherical, blue-blackdrupe, 6–8 mm (1⁄4–5⁄16 in) diameter; it is edible, though thin-fleshed.[6]
It is one of two species in the genusWashingtonia. The other is the close relativeWashingtonia filifera, which occupies a more northerly distribution. Compared withW. 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 theSierra de La Asamblea and theBaja California desert south into theVizcaino region and theSierra de La Giganta, and into the southern cape.[8] InSonora, it occurs in canyons in the western half of the state, particularly in the palm oases of the Sierra El Aguaje north ofGuaymas. It is relatively restricted, and is suspected to be arelict population in Sonora. It has the fewest plants in the palm oases that are shared with two other more numerous species,Brahea brandegeei andSabal uresana.[7]
Like the closely relatedWashingtonia filifera (California fan palm), it is grown as anornamental 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).[citation needed]
Field research conducted onW. 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.[citation needed]
The Mexican fan palm is normally grown in the desertSouthwestern United States, in areas such asCalifornia,Arizona,southern Nevada, extreme southwesternUtah andTexas. It also cultivated in the coastal areas of South Atlantic states and the Gulf Coast, including southernNorth Carolina, coastalSouth Carolina, southernGeorgia, andFlorida. Along the Gulf Coast, Mexican fan palms can be found growing along the Florida west coast westward toSouth Texas.[citation needed]
Washingtonia × filibusta is ahybrid ofW. robusta andW. filifera, and has intermediate characteristics of the two parents, especially greater tolerance of wet cold.[11]
Like the relatedW. 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, whenW. robusta is cultivated, its skirt of heavy, dry, dead leaves is typically cut ("trimming"), and then the leaf bases are removed to give the trunk a relatively smooth, uniform appearance ("skinning") 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, theCalifornia Department of Public Health developed a series of reports and training materials to prevent accidents while trimming tall skirt-bearing palms such asW. robusta.[12]
