Types of Palm Species:

Cotton Palm (Washingtonia robusta)

http://itp.lucidcentral.org/id/palms/palm-id/Washingtonia_robusta.htm

Common Names: Mexican Fan Palm, Washingtonia Palm, Skyduster Description

Stems: Single Taper trunk upright to 22 m tall and 80 cm diameter, covered with a skirt of dead leaves (unless removed for landscape appeal). Old leaf bases usually fall away after many years, to leave a smooth gray stem with closely spaced leaf scar rings.

Leaves: Costapalmate, induplicate, split about half the blade length into numerous segments with stiff tips and threads (marginal fibers) hanging between segments. Many bright green leaves form a full crown.

Petioles: Armed with curved teeth along orange-colored margins. The adaxial hastula is prominent with tattered, papery margins. The base of the lower surface of the leaf blade densely covered with near white pubescence.

Reproductive characters: Inflorescences are numerous, branched to at least three orders, and project from the crown extending beyond the leaves. Individual flowers are bisexual, white. Fruits are spherical to pear-shaped, up to 1 cm in diameter, and brownish-black to black when ripe.

Diagnostic Features:

Tapered stem, roughly twice as wide at the base as the crown, and bright green leaves forming a dense crown May be confused with:Washingtonia filifera, but that species has a massive, columnar stem and grayish-green leaves forming an open crown while W. robusta has tapered stems, bright or somewhat olive green leaves with shorter petioles forming a dense crown

Distribution:  Native to northwestern Mexico  

California Fan Palm (Washingtonia filifera)

Common Name: California Fan Palm, Desert Fan Palmhttp://itp.lucidcentral.org/id/palms/palm-id/Washingtonia_filifera.htm   

Description:

Stems: Solitary, columnar, upright to 15 m tall and 100-150 cm diameter, covered with a skirt of marcescent leaves (unless removed for landscape appeal). Old leaf bases usually fall away after many years, to leave a smooth gray stem with closely spaced leaf scar rings. Leaves: Several grayish-green leaves form an open crown. Petioles split, armed with curved teeth. The base of the lower surface of the leaf blade scantly covered with near white pubescence. The adaxial hastula is prominent with tattered margins.

Flowers and fruits: Inflorescences are numerous, branched to at least three orders, and project from the crown extending beyond the leaves. Individual flowers are bisexual, white. Fruits are spherical to pear-shaped, up to 1 cm in diameter, and brownish-black to black when ripe. 

Diagnostic Features in the Field: Solitary, columnar, upright to 15 m tall and 100-150 cm diameter, covered with a skirt of marcescent leaves. Washingtonia filifera has an open crown of grayish green, costapalmate leaves with armed petioles split at the base. 

May be confused with:  Washingtonia robusta, but that species has a tapered stem, roughly twice as wide at the base as the apex, and bright green leaves forming a dense crown, rather than the columnar stemmed W. filifera, with grayish-green leaves and long petioles forming an open crown.