BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Fouquieria splendens | Ocotillo 



GENERAL BOTANICAL CHARACTERISTICS : 
Ocotillo is a drought-deciduous shrub with 6 to 100 wandlike branches
that arise from the root crown.  Stems are 9 to 30 feet (2-9 m) tall
with spines to 1.5 inches (4 cm) long.  Leaves grow to 2 inches (5 cm)
long and are thick and leathery.  Leaf abscission occurs under water
stress so ocotillo appears leafless most of the year, but it quickly
refoliates after rain [24,29,43,49,69].  Four or five crops of leaves may
be produced annually [33,36].  The leaves mature within a few weeks and
are then shed [36,49].  Ocotillo is dormant when leafless and is
protected from further water loss by its waterproof bark [36].  The
bisexual scarlet flowers are clustered at the stem tips in a panicle and
often appear before the leaves in spring.  The fruit is a capsule that
contains numerous, winged seeds [24,43,49,69].

The root system of ocotillo is shallow with a few laterals branching
from the main taproot just below the soil surface [11,36,76].  Taproots
penetrated to a depth of 3 to 6 inches (8-15 cm) on adobe clay underlain
by caliche on the bajada of Tumamoc Hill near Tucson, Arizona [11].

Ocotillo has the physical capacity to produce leaves without the
concurrent movement of nutrients or hormones from the roots, and without
addition of exogenous nutrients or hormones.  The process is dependent
of water availability.  Cut ocotillo stems decoupled from root activity
began to refoliate within 24 hours after being placed in water, even
after months of dry storage.  The largest leaves were approximately 1
inch (2.4 cm) long within 8 days.  The cut stems did not produce roots
[31], although stem cuttings are known to sprout [29,69].

Ocotillo has extrafloral nectaries (nectar-secreting glands) located on
the flower buds that may promote mutualistic interactions with insects.
Insects gain nutrients and water while ocotillo gains decreased
herbivory [48], particularly during the reproductive period


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Ocotillo reproduces by basal sprouting [73,78] and sprouting from stem
cuttings [29,69].

Ocotillo flowers produce nectar and are pollinated by hummingbirds and
bees.  Ocotillo may self pollinate to a limited extent.  In southern
Arizona flowering coincides with the northward migration of
hummingbirds.  Seed set per flower is greater for plants flowering
during migration than for plants flowering after hummingbirds have
migrated [50,72].

Freeman [16] stated that each ocotillo plant produces at most a few
hundred highly viable seeds (viability of 90%) per year that are known
to germinate after rain.  Germination remains relatively high (about
40%) even after 8 days of exposure to temperatures of 104 degrees
Fahrenheit (40 deg C) for 12 hours each day.  This lack of sensitivity
to high temperatures suggests that ocotillo can germinate readily after
late summer rains.  Ocotillo seeds probably do not survive for long in
the soil.  Ocotillo probably requires a sequence of favorable conditions
to regenerate well, such as heavy winter rain for seed production
followed by heavy summer rain for seedling establishment [78].  Shreve
[55] reported that ocotillo had low and erratic seedling establishment
and a large amount of seedling mortality due to moisture stress.  After
summer rains extremely high densities of seedlings (more than 100/sq m)
were observed, but less than 1 percent of those survived to 1 year of
age.  Survival from year 1 to 7 was approximately 27 percent.  No
ocotillo seedlings were found in the months following heavy September
rainfall in a desert community in San Diego County, California [78].

The winged seeds of ocotillo are probably wind dispersed.

Ocotillo recruitment has a positive significant (p<0.05) association
with triangle bursage (Ambrosia deltoidea) in desert shrub communities
in Arizona [39].


SITE CHARACTERISTICS : 
Ocotillo is found on dry, well-drained, rocky slopes, mesas, bajadas,
outwash plains, and valleys in desert shrub and desert grassland
habitats [8,13,23,26,29,69,71].  Soils are generally rocky, shallow, and
of limestone or granitic origin and are often underlain by caliche
[26,40,71].  Ocotillo generally occurs from sea level to approximately
5,200 feet (1,600 m) elevation [16,26,72].  It may reach its upper
elevational limits 900 to 1,500 feet (270-450 m) higher on limestone
than on granitic soils [56].  In the Guadalupe and Del Norte mountains
of the Trans-Pecos region of Texas, ocotillo is found on limestone
ridgetops, outcrops, and slopes, at elevations as high as 6,700 feet
(2,050 m) [10,12,32].  Ocotillo may also occur at higher elevations in
oak woodlands above desert grassland communities [37,45].  Aspect is
generally south or southeast, where surface temperatures allow daily
thawing even with freezing air temperatures above the surface layer
[10].

In the Sonoran Desert ocotillo is found from the valley plains to upper
bajadas at elevations up to 2,300 feet (700 m).  It is probably more
abundant on the upper bajadas due to rapid infiltration and thus greater
available soil moisture in the coarse rocky upland soils than in the
heavy silt loams of the valley plains [70].


SUCCESSIONAL STATUS : 
Little information is available on the successional status of ocotillo.
Seedlings are rarely found on disturbed soils [76] but are found under
the canopy of mature plants [39,77].  Zedler [78] stated that ocotillo
is a long-lived stable element of desert vegetation with specialized
requirements for seed germination that limit its capacity to exploit
opportunities for population expansion.  Shreve [58] reported that the
rate of growth and mortality of ocotillo are high and that its life span
probably does not exceed 60 years.  Others have observed ocotillo plants
that were 72+ years old [20].

Ocotillo persisted on eroded clay beds on a few inches to 1 foot (30 cm)
of soil in the early stages of erosion at the Tornilla Clay Beds, Texas
[42].  


SEASONAL DEVELOPMENT : 
Ocotillo generally flowers from March to June depending on latitude
[29,43,49].  In southern Arizona ocotillo produces flowers from March to
May and flowering generally lasts 50 to 60 days.  Seed drop occurs from
May to mid-June [72].

The following phenological pattern was observed in ocotillo on an upper
bajada in the Chihuahuan Desert in New Mexico between July 1978 and June
1980 [30]:
             
  September-October, 1978 --growth of new leaves
   October-November, 1978 --leaf abscission
              April, 1979 --initiation of flower buds
          April-May, 1979 --flowering
                May, 1979 --growth of new leaves
          June-July, 1979 --mature fruits
        July-August, 1979 --leaf yellowing
   August-September, 1979 --growth of new leaves
            October, 1979 --leaf abscission
              April, 1980 --initiation of flower buds
          April-May, 1980 --flowering
                May, 1980 --growth of new leaves
               June, 1980 --mature fruits

Related categories for Species: Fouquieria splendens | Ocotillo