Washingtonia H.Wendl.
  • Bot. Zeitung (Berlin) 37: 68 (1879) 

Notes: , nom. cons. Distribution: SW. U.S.A. to NW. Mexico

General Description

Robust, tall, solitary, armed, pleonanthic, hermaphroditic tree palms. Stem erect, usually partly or wholly covered with persistent dry leaves, ringed with close leaf scars, sometimes enlarged basally. Leaves induplicate, costapalmate, marcescent; sheath with a conspicuous abaxial cleft below the petiole, the margins disintegrating into a dark-brown fibrous network, the sheath densely caducous tomentose, margins becoming fibrous; petiole elongate, adaxially flattened to slightly concave, abaxially rounded, margins strongly armed with curved teeth, teeth becoming smaller and sparser distally; adaxial hastula large, membranous, triangular, irregularly margined and tattering, abaxial hastula a low ridge obscured by a mat of thick tomentum (in Washingtonia robusta); blade divided irregularly to ca. 1/3 its length into linear single-fold segments, bifid at their apices, pendulous at maturity, filamentous at the tips, interfold filaments conspicuous, midribs prominent abaxially, transverse veinlets obscure. Inflorescence interfoliar, ascending, branched to 3(–4) orders, equalling or generally exceeding the leaves, curved, slender; peduncle short; prophyll tubular, closely sheathing, 2-keeled, irregularly tattered at the tip; peduncular bract 1, like the prophyll but with a single keel; rachis much longer than the peduncle; rachis bracts tubular basally, splitting longitudinally, becoming flattened and sword-like, very coriaceous; subsequent bracts minute or lacking; rachillae numerous, short, very slender, glabrous. Flowers solitary, elongate, spirally inserted, briefly pedicellate; calyx chaffy, tubular proximally with 3 irregularly tattered, imbricate lobes, persistent in fruit; corolla tubular for ca. 1/3 its length, distinct lobes valvate, narrowly ovate, tapering to a point, reflexed at anthesis, thin, almost chaffy; stamens 6, borne at the mouth of corolla tube, filaments elongate, gradually tapering from a fleshy base, anthers elongate, medifixed, versatile, latrorse, connective narrow; gynoecium top-shaped, carpels 3, distinct basally, united through the long slender styles, ovule basal, erect, (?)anatropous. Pollen ellipsoidal, with slight to extreme asymmetry; aperture a distal sulcus; ectexine tectate, rugulate or reticulate, aperture margin slightly finer; infratectum columellate; longest axis 35–51 µm; post-meiotic tetrads tetrahedral, tetragonal or decussate, proportions not recorded [2/2]. Fruit small, broadly ellipsoidal to globose, often falling with the pedicel and unilaterally ruptured calyx tube attached, blackish, stigmatic and abortive carpel remains apical; epicarp smooth, thin, mesocarp thin, fleshy with a few flattened longitudinal fibres, endocarp thin, crustaceous, not adherent to the seed, smooth within. Seed ellipsoidal, somewhat compressed, hilum eccentrically basal, raphe extending 2/3 the length of the shining red-brown seed coat, loosely branched laterally, seed coat intrusion very thin, endosperm homogeneous; embryo basal. Germination remote-ligular; eophyll entire, lanceolate. Cytology: 2n = 36.

Diagnostic Description

Striking solitary hermaphroditic tree fan palms native to desert oases in southwestern USA and northwestern Mexico, distinctive in the long inflorescences with bracts that split and open out, becoming almost sword-like, and the chaffy petals and sepals.


Leaf (Tomlinson 1961), roots (Seubert 1997), floral (Morrow 1965).


Desert palms occurring along streams and canyons, also about springs and seepages in more open areas.


Two closely related species: Washingtonia filifera occurs in southeastern California, western Arizona, and Baja California; W. robusta in Baja California and Sonora, Mexico.

Common Names

Washington palms, desert fan palm (Washingtonia filifera), Mexican washington (W. robusta).

Distribution Map

  • Native distribution
  • Introduced distribution
Found in
  • Australasia New Zealand New Zealand North
  • Northern America Mexico Mexico Northwest
  • Southwestern U.S.A. Arizona
  • California
Introduced into
  • Africa Macaronesia Canary Is.
  • Western Indian Ocean Réunion
  • Australasia Australia New South Wales
  • Europe Southwestern Europe Spain
  • Northern America Southeastern U.S.A. Florida
  • Southwestern U.S.A. Nevada
  • Pacific North-Central Pacific Hawaii


  • 1 J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008
  • 2 Govaerts, R. & Dransfield, J. (2005). World Checklist of Palms: 1-223. The Board of Trustees of the Royal Botanic Gardens, Kew.

 Information From

Palmweb - Palms of the World Online
Palmweb 2011. Palmweb: Palms of the World Online. Published on the internet http://www.palmweb.org. Accessed on 21/04/2013
  • A Content licensed under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License
  • B http://creativecommons.org/publicdomain/zero/1.0
eMonocot. (2010, 1st November). Retrieved Wednesday, 8th February, 2012, from http://e-monocot.org.
  • C Content licensed under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License
World Checklist of Selected Plant Families
WCSP 2014. 'World Checklist of Selected Plant Families. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; http://apps.kew.org/wcsp/ Retrieved 2011 onwards
  • D See http://kew.org/about-kew/website-information/legal-notices/index.htm You may use data on these Terms and Conditions and on further condition that: The data is not used for commercial purposes; You may copy and retain data solely for scholarly, educational or research purposes; You may not publish our data, except for small extracts provided for illustrative purposes and duly acknowledged; You acknowledge the source of the data by the words "With the permission of the Trustees of the Royal Botanic Gardens, Kew" in a position which is reasonably prominent in view of your use of the data; Any other use of data or any other content from this website may only be made with our prior written agreement.