BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Washingtonia filifera | California Palm 



GENERAL BOTANICAL CHARACTERISTICS : 
California plam is a native evergreen monocot from 30 to 50 feet (9-15
m) in height and 1 to 2 feet (0.3-0.6 m) in diameter.  The crown is a
rosette of large leaves.  It is supported by a columnar trunk.  Unburned
trunks are covered by a mass of pendent dead leaves called a shag or
skirt.  Outer trunk tissue consists of a thick, barklike rind.  The
inflorescense is a spadix.  The fruit is a drupe containing a single
large seed [28,32,33].  California palm is a phreatophtye [40].  Roots
are variously described in the literature as shallow [1] or deep [28].
Presumably, root depth varies with depth of the water table, with palms
growing near seeps and springs having the more shallow root systems.
Determining the exact age of palms is difficult because tree-ring counts
cannot be made on monocots.  The maximum age attained by this species is
estimated to be 200 years.  Mature trees typically live about 150 years
[40].  California palm can withstand about 22 hours of subfreezing
temperature [9].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
California palm regenerates from seed [12]; vegetative reproduction does
not occur (J. W. Cornett, in [22]).  Cultivated trees have flowered at
age 19 [26], but the age at which trees growing under natural conditions
first flower is unreported.  Pollination is predominantly
insect-mediated (J. W. Cornett, in [22]), but self-pollination may also
occur [22].  Natural populations of California palm are reseeding well
[23].  A heavy crop for an individual tree probably approaches 10,000
fruits.  In the southern Anza-Borrego region of California, 11 percent
of trees fruited 1 year, followed by 57 to 59 percent of trees fruiting
in the following 3 years [6].  Seeds are disseminated primarily by the
coyote [7,40].  Because of its fruit-eating habit and broad range of
travel between water sources, coyote often transport seeds over
considerable distances [32].  The four California palm groves of
southern Nevada probably established from seed in coyote scat [7].  A
comparison of seed collected from the ground surface and seed collected
from coyote scat showed that the pericarp was missing from 94 percent of
coyote-consumed seed.  Removal of the pericarp increases the probability
of germination.  Sixty-three percent of coyote-consumed seed tested in
this study germinated, as compared to 34 percent of that in the control
group [8].  Seed in coyote scat are rarely comsumed by passing animals
[7].  Gray fox also consume and disseminate seed.  Birds generally
consume only the fruit, not the seed [32].  The western and mountain
bluebird and the cedar waxwing, however, eat both fruit and seed,
disseminating the seed in droppings.  Seed in bird droppings are usually
disseminated within or close by the grove of the parent tree.  The seed
appears to be difficult for these birds to digest, and are often
regurgitated.  Regurgitated seed may still be partially covered by fruit
fragments, which reduces germination rates.  Rodent predation of seed in
bird droppings or vomit is high [6].  Seed remains viable in seedbanks
for up to 6 years [19].  Germination is hypogeal [36].  Seedlings
require a moist mineral seedbed and partial shade to full sun.  They
cannot establish on highly alkaline soils [39].  Seedling recruitment
frequently occurs in a flush during wet years [40].

California palm fruit allelopathically inhibits germination and growth of
other species under laboratory conditions [7].


SITE CHARACTERISTICS : 
Topography and soils:  California palm occurs at elevations below 3,500
feet (1,067 m) [24].  It serves as an indicator species, denoting
sources of year-round surface water in desert [22,33]; it is found near
seeps, springs, and streams [33].  It also occurs in canyons where water
is channeled from nearby mountains, in alluvial fan edges where
groundwater is trapped by bedrock, and where water percolates through
rock fractures caused by earthquake faulting [32].  Soils are generally
undeveloped and low in organic matter except in densely vegetated oases.
Hillside oases soils consist of lacustrine sediments of mud and rock,
while wash oases soils also contain sand.  Seep oases have fine,
flocculent soils and are frequently covered by a thin crust of salts,
which tends to minimize soil erosion.  If such soils are thickly
crusted, undergrowth is sparse or absent.  Most soils supporting
California palm are high in pH (average pH 9.2) [40].  Soils in its root
zone, however, are generally less alkaline than topsoils [33].

Climate:  California palm grows in a semiarid climate.  Temperatures are
typically hot in summer (average 107 degrees Fahrenheit [42 deg C]) and
below freezing in winter.  Temperature extremes recorded near one
Colorado Desert oasis are 13 and 125 degrees Fahrenheit (-17 and 52 deg
C).  Oases temperatures are generally more moderate than the open
desert, being cooler in summer and warmer in winter.  Average annual
precipitation ranges from 3 inches (8 cm) at the lowest to 8 inches (20
cm) at the highest elevations of California palm's range.  Most
precipitation falls from December to March, but locally beneficial rains
occur from July through September.  Lightning is common during such
storms [40].

Plant associates:  Overstory associates not listed under Distribution
and Occurrence include Fremont cottonwood (Populus fremontii),
saltcedar, paloverde (Cercidium floridum), and California sycamore
(Plantus racemosa) [7,30,40].  Understory associates include cattail
(Typha spp.), reed (Phragmites australis), cane (Arundinaria spp.),
Olney bulrush (Scirpus olneyi), Torrey seepweed (Suaeda torreyana),
desert willow (Salix gooddingii), arrowweed (Pluchea sericea), saltgrass
(Distichlis spp), mesquite, alkali sacaton (Sporobolus airoides), alkali
goldenbush (Haplopappus acradenius), desert holly (Atriplex
hymenelytra), and allscale saltbush (A. polycarpa) [1,7,24,30,40].


SUCCESSIONAL STATUS : 
Obligate Initial Community Species

California palm is moderately shade tolerant when young, becoming
intolerant with age [28,40].  California palm communities require moist
pioneer conditions [40].  They are invaded by shrubs in the absence of
fire, creating environmental conditions which eventually kill the palms
[1,40].  (See Management Considerations and Fire Management
Considerations.)


SEASONAL DEVELOPMENT : 
Flowering occurs in May and June [32].  The leaves die at the end of the
summer growing season, remaining attached to the trunk [33].  Fruits
ripen in September [23], and seeds ripen and drop from November to
January [19,6].

Related categories for Species: Washingtonia filifera | California Palm