Washingtonia

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Washingtonia is a genus of palms, native to the southwestern United States (in southern California, and southwest Arizona) and northwest Mexico (in Baja California and Sonora).<ref name=r/><ref>Jon P. Rebman, Judy Gibson, and Karen Rich. Annotated checklist of the vascular plants of Baja California, Mexico. 2016. Proceedings of the San Diego Society of Natural History. number 45. page 275. </ref> Both Washingtonia species are commonly cultivated across the Southern United States, the Middle East, southern Europe, and North Africa, where they have greatly hybridized.

Description

They are fan palms (subfamily Coryphoideae), with petioles armed with sharp thorns terminating in a rounded fan of numerous leaflets. The flowers are in a dense inflorescence, with the fruits maturing into a small blackish-brown drupe 6–10 mm diameter with a thin layer of sweet flesh over the single seed.<ref name=riffle>Riffle, Robert L. and Craft, Paul (2003) An Encyclopedia of Cultivated Palms. Portland: Timber Press. Template:ISBN / Template:ISBN</ref>

Extant species

There are two recognized species in the genus Washingtonia: W. filifera and W. robusta. The commonly cultivated W. × filibusta is a hybrid between the two. Some recent research has suggested that these taxa may instead represent a single species with a gradient of subspecies.<ref>https://escholarship.org/uc/item/8w96266q</ref>

Species	Description	Current distribution
California fan palm or desert fan palm Washingtonia filifera (Lindl. ex André) H.Wendl. A grove of Washingtonia filifera in Castle Creek, Arizona	Tree to 23 m tall; leaves large, with petiole up to 2 m long, and leaflets up to 2 m long. Inflorescence to 5 m long; flowers white; fruit oval. Palms are often found at the base of mountains, hills and form around desert oasis in the southwest. They are used in landscaping, particularly in southern counties of California.	Southwestern USA, just into extreme northwest Mexico.
Washingtonia × filibusta	This Washingtonia is a hybrid between the robusta and filifera
Mexican fan palm or skyduster palm Washingtonia robusta H.Wendl.	Tree to 25 m tall; leaves smaller, with petiole up to 1 m long, and leaflets up to 1 m long. Inflorescence to 3 m long; flowers pale orange-pink; fruit spherical.	Northwest Mexico. (Teresa Ribeiro et al.).

The fruit is edible, and was used by Native American people as a minor food source. They are also eaten by birds, which disperse the seeds in their droppings after digesting the fruit pulp. Washingtonia species are also used as food plants by the larvae of some Lepidoptera species, including Paysandisia archon.

Both species are cultivated as ornamental trees, widely planted in California, Florida, Texas, extreme southwest Utah, Arizona, southern New Mexico, South Carolina, and southern areas of North Carolina. It is also cultivated in the Mediterranean region in southern Europe and north Africa, parts of Australia, and the leeward sides of the Hawaiian Islands. W. filifera is modestly hardy in drier climate and able to survive brief temperatures in the vicinity of -15 °C (10 °F), provided the air and soil are not too wet, and the afternoon temperatures are not too cold. Intolerance of wet, prolonged cold is the main reason the filifera species cannot grow in temperate climates. W. robusta is less sensitive to moisture than filifera, but far more easily damaged by cold.