Washingtonia filifera (Linden) Wendl., Arecaceae

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Present on Pacific Islands?  no

Primarily a threat at high elevations?  no

Risk assessment results:  High risk, score: 11.5 (Go to the risk assessment)

Common name(s): [more details]

English: California fan palm, California washingtonia, Washington palm, cotton palm, desert fan palm, northern fan palm, petticoat palm

French: palmier évantail de Californie

Habit:  tree

Description:  "Sex: Hermaphrodite.  Trunk: To 50 ft. fall; thick, to 3 ft. diameter; not enlarged at base; upper part, or sometimes all the trunk, covered with a huge shag or petticoat of dead leaves.  If leaves are cut off, the leafbases form a covering for the trunk, compact, but with no regular pattern.  The gray surface of trunk, if exposed, is marked with vertical chinks or ridges that are more prominent than the rings.  Petiole: Long, to 6 ft.; 6 in. broad near base; margins armed with prominent teeth; green in color; leafbases are sometimes brown or reddish.  Leaf: To 6 ft. or more across; divided more than halfway to base; many long threads attached to segments and sinuses throughout life of tree.  Segments: 50 or more gray-green; not glaucous.  Flowerstalk: From lower leaves; 9-12 ft. long; erect at first, then hanging with fruit, and eventually becoming involved in the shag of dead leaves, of which it becomes a part.  Flowers: Small; numerous; white.  Fruit: 1/3 in. long, 1/4 in. broad; ovoid; lightly wrinkled.  Seed: Single; same shape as fruit, but trifle smaller" (McCarrach, 1960; p. 264).

Key to species of Washingtonia (from Oppenheimer & Bartlett, 2002; p. 3):
Trunk slender, tapered from a stout base; leaf blades bright green, hastula tawny beneath:  Washingtonia robusta.
Trunk stout without a broader base; leaf blades gray-green, lacking a tawny patch beneath the hastula:  Washingtonia filifera.

Habitat/ecology:  "Groves, moist places, seeps, springs, stream sides; to 1200 m" (Hickman, 1993; p. 1105). Adaptable to a wide range of soils and climates. Can grow in extreme alkaline soils that have a pH as high as 9.2.  Considered very disease and pest resistant and quite resistant to lethal yellowing disease. Prefers exposure to full sun but also grows well in part sun/shade. Drought tolerant and can withstand frosts and freezes as well as extreme heat (Floridata).

Propagation:  Seed

Native range:  "Southern California, western Arizona, northwestern Mexico" (McCarrach, 1960; p. 264).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced invasive cultivated	Atkinson, Rachel/Sawyer, John (2011)
Chile (offshore islands) Juan Fernández Islands	Isla Más a Tierra (Robinson Crusoe Island)	introduced cultivated	Danton, Philippe/Perrier, Christophe/Martinez Reyes, Guido (2006) (pp. 501-502, 547-548, 558) "Su reciente introducción en RC (Hotel Pangal en 2000) no permite hacerse una idea de su comportamiento en el futuro. Es una especie que debe ser vigilada de cerca. Un lote de plantas tamiento en el futuro. Un lote de plantas jóvenes llegó a la isla en 2005; fueron plantados en varios lugares del pueblo de San Juan Bautista. La Isla teniendo una palmera endémica (Juania australia), seria mejor fomentar su cultivo en lugar de introducir especies exóticas".
Guam Guam Island	Guam Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 89)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Oppenheimer, Hank L./Bartlett, Randal T. (2002) (p. 3) West Maui. Voucher cited: Oppenheimer H30016 (BISH)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive cultivated	Frohlich, Danielle/Lau, Alex (2010) (p. 5) Voucher cited: D. Frohlich & A. Lau 2008072401 (BISH)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia Australia (continental)	New South Wales		Palmweb (2013)
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Singapore Singapore	Singapore (Republic of)	introduced cultivated	Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. (2009) (p. 90) Cultivated only
United States (west coast) United States (west coast states)	USA (California)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)

Control:  If you know of control methods for Washingtonia filifera, please let us know.