DescriptionStately and distinctive, the California fan palm is one of the most widely grown palms in subtropical climates. California fan palm can grow 60' tall with a crown spread of 15'. The massive gray trunk is barrel shaped and ringed with old leaf scars, and may reach over 3' in diameter at its widest point. California fan palm can have up to thirty gray-green palmate (fan-shaped) leaves, each 3-6' across. They spread out to form a loose and open crown. The petioles (leaf stems) of mature palms are armed along the margins with curved thorns; those of young palms are largely unarmed. The individual leaflets are pendulous and swing freely in the wind. Abundant cotton-like threads on and between the leaflets persist even when the palm is mature. If old leaves are not removed, they form a continuous "petticoat" from the crown all the way to the ground. The California fan palm produces numerous branching flower clusters that project out and often downward from the leaf crown. The bisexual blossoms are white and yellow and give rise to oblong or round red-black fruit, each about a half inch in diameter. The fruits of California fan palm contain a single seed, approximately 1/4" in diameter.
The Mexican fan palm (Washingtonia robusta) and the California fan palm are closely related and quite similar. They differ in subtle characteristics, and even palm experts have trouble telling them apart. This table provides some distinguishing characteristics:
| Washingtonia filifera (California fan palm) |
Washingtonia robusta (Mexican fan palm) |
|
| Petioles (leafstems) of young palms | are green and relatively unarmed (no thorns) | are brown and distinctly thorny |
| Basal sheath (bottom of the base of the leaf blade) | does NOT have a bright tawny-colored patch | has a bright tawny-colored patch |
| Crown (of mature specimans) | has leaves in a loose and open arrangement | is dense and compact |
| Leaflets | are pendulous and swinging (not stiff), and the cottony threads persist | are stiff and their cottony threads fall off with age |
| Trunk | is barrel shaped and the palm rarely exceeds 60' in height | is slender (slightly swollen at the base) and can get 100' tall |
Location
California fan palm grows naturally in desert and arid regions, along
streams and canyons, and in open areas where groundwater is present in
southern California, western Arizona, and Baja California in Mexico.
Culture
This widely grown palm succeeds admirably in a wide range of soils and
climates. California fan palm can grow in extreme alkaline soils that have a
pH as high as 9.2. Even large California fan palms can be successfully
transplanted. California fan palms respond very well to fertilizer. A slow
release fertilizer may be used during the summer growing season. Some
growers fertilize their palms monthly with a general purpose plant food or a
plant food specifically formulated for palms. One enthusiast used a monthly
application of Miracle Grow fertilizer to grow a California fan palm with a
trunk diameter of 40" - the largest known. The vigorous and robust
California fan palm is considered very disease and pest resistant, and is
quite resistant to lethal yellowing disease. As with other palms, potassium
and magnesium deficiencies may occur in California fan palms and mineral
supplements should be administered in recommended amounts to prevent or
treat such deficiencies.
Light: California fan palm prefers exposure to full sun and even
quite small specimens will thrive in full sun. It also grows well in part
sun/shade.
Moisture: Once established, California fan palm is drought tolerant,
but it benefits greatly with regular watering. For optimal growth, soil
should be moist with good drainage.
Hardiness: USDA Zones 8B - 11. Established California fan palms can
withstand frosts and freezes. Reports of cold hardiness for the California
fan palm indicate the tree withstands 15-20 F with only minor foliage
damage. Many enthusiasts are now growing and recommending the California fan
palm in USDA Zone 8A. Mature and established plants have survived -11 F, but
such very low temperatures can be expected to cause major and significant
foliage damage. Palms in fast-draining soil are more cold hardy. During the
winter, leaves may become temporarily discolored by damp cold and frost.
California fan palms can withstand extreme heat, too, including temperatures
up to 127 F.
Propagation: California fan palm is easy to grow from seed. Even old
seeds are reported to germinate well. Germination is considered so easy that
young plants may become weeds under mature palms.
Usage
Plant California fan palm outdoors in a site that can accommodate the large
head of leaves, and is not directly under power lines or other structures.
Use the California fan palm in natural and formal groupings and in large
open areas. California fan palm is perfect for street, avenue and parkland
planting where it typically is spaced about 30' apart. Young California fan
palms also can be grown in pots or tubs on decks or in indoor areas, such as
conservatories or atriums that have bright light.
Features
The California fan palm has numerous fine attributes including cold
hardiness, fast growth and drought and salt resistance. This palm is
inexpensive, adapts to most soils, is easy to grow and transplant, and is
very hardy. The genus was named in honor of George Washington. The species
name, filifera, comes from both Latin and Greek words meaning
thread-bearing.