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Plants of Baja
Your guides will give
entertaining, informative presentations on desert plants and ecology. Trips
also carry an extensive library with books on plants.
Two-thirds of Baja
California is within the Sonoran Desert - the hottest, wettest and biologically
richest of North America's four arid ecosystems (the Chihuahuan, Great Basin
and Mojave deserts complete the set). The Sonoran Desert extends over 12
degrees of latitude, from roughly 23 degrees north, on the tip of Baja, to 35
degrees N, on the border between Arizona and California. Another portion covers
more than half the Mexican State of Sonora. It is a young desert and has
probably existed for no more than 10,000 years.
Here, two rainy seasons,
one in winter and the other in late summer, create North America's only
subtropical desert. "Rainy" is a relative term, since less than 10 inches fall
on average in Baja each year. Despite that, nearly 2500 plant species populate
this so-called wasteland, and the landscape is surprisingly lush and green,
brimming with palo verde trees and tangled mesquite shrubs. Tall-stalked agaves
and the waving tendrils of ocotillos add to the exotic aura. But cacti
dominate.
Columns of cardons
dominate the horizon, quivering in the hot thermals amid clustered stalks of
organ pipes and spiny cholla (pronounced Choy-a). Tiny clusters of round
hedgehog cactus peak from beneath sheltering tangles of creosote bush. Barrel
cactus usually leans to the south towards the most intense light, therefore its
name "compass cactus". All are arrayed at regular intervals, as competition for
water is fierce; each plant claims a small expanse of desert, and guards that
area jealously with root toxins.
Their prehistoric
appearance not withstanding, cacti haven't spent much time on this earth. Like
the Sonoran Desert itself, the cactus family is a recent phenomenon, having
evolved from tropical roses no more than 50,000 years ago. Modern cactus
species are strictly New World natives. On the evolutionary scale, they are a
family still in transition, colonizing and hybridizing rapidly. The ubiquitous
prickly pear with its signature flat, oval pads is the most widespread of the
cacti, thriving from the southern tip of South America and northward through
Canada to sand dunes rimming the Arctic Circle. Nowadays, the more productive
species of prickly pear are valued for their thin pads, called nopales, and are
raised commercially in Mexico for food.
To cope with aridity,
desert plants employ a variety of strategies. Waxy coatings and reduced leaf
size limits evaporation. Plants can respond to drought by going dormant or,
like the Ocotillo, they may shed and regrow leaves several times a year in
response to available moisture. Many desert plants are drought-escaping annuals
whose seeds only germinate when there is a rainy year. The perennials are often
slow growing, low in stature, and widely spaced, reducing competition for water
and light.
Structural modifications
for the collection, extraction, conservation, and storage of water allow desert
plants to survive. The most striking aspect of many cacti is their fleshy,
jointed trunk covered with a woody, green cuticle. A waxy evaporation resistant
layer over the cuticle helps protect the plant against dehydration. Cactus
spines are modified leaves that protect the plant from being eaten and serve to
break up the sun's rays. Pleated ribs also provide shade for 50 percent of the
stem's surface area. Some cactus species have a woody skeleton for internal
support.
Cacti have shallow,
spreading root systems that radiate far from the plant, but seldom penetrate
the soil more than a foot. During times of abundant rain, the primary roots
sprout additional rain roots that can emerge literally overnight. The funnel
shape of the agave channels water directly to its roots.
The pleated trunks and
oval pads of cacti and other succulent plants are designed to seize these
windfalls of moisture. Up to 95 percent of many cacti's total volume is water,
which is contained in a thickened mucilaginous substance that decreases the
rate of evaporation. Accordion pleats allow a cardon to expand and contract as
the rainy season gives way to long dry spells. After a drenching rainfall, this
stately giant could swell another 15 percent beyond its original diameter. By
late autumn, its shadow might be a third thinner. Some cacti can sustain a
60-70 percent moisture loss without damage and survive years with no
rainfall.
To survive in
inhospitable surroundings, a cactus holds it breath all day long. It opens
respiratory skin pores called stomates only at night, a neat evolutionary trick
that keeps the evaporation of precious fluid to a minimum. Carbon dioxide for
the day's photosynthesis is gathered then and stored for the day. Oxygen, a
by-product of photosynthesis, must be held in the plant's tissues until
evening's sigh of relief. Most photosynthesis occurs in the fleshy stems or
trunks.
Cacti require more than
a single season to mature. A cardon may not flower until its 50th year. Each
flower opens just one night and a day, thereby taking advantage of both night
pollinators such as nectar seeking bats and day pollinators. All flowers are
wheel- or funnel-shaped, and the resulting fruits contain numerous tiny seeds.
The fruits of all cactus species are edible.
This was important for
the early inhabitants of Baja, for cactus fruits form one of the Sonoran's only
late-summer food sources. The fruit of the organ pipe cactus (or pitaya dulce)
were once a staple food for the Indians. They even ate seeds picked from dried
feces, prompting Spanish missionaries to call it the "fruit of the second
harvest". It is still eagerly sought after in Baja for its sweet flavor, often
made into marmalades and wines.
The cardon blooming
overhead may produce 40 or 50 fruits each year once its brief, snow-white
blossoms have dried. Of the 22 million seeds a cardon produces in its lifetime,
few will have the opportunity to germinate because every creature in this harsh
world covets the nutrients stored within. Only seeds that land in the shade of
a nursery tree like ironwood or torote stand a chance of germinating, and for
those seedlings fortunate enough to break ground, the average lifespan still is
less than six weeks. Even these toughest of plants can't survive their youth
without shelter from the sun.
If conditions are right,
a cardon will live to 200 years and grow up to 60 feet tall, making it the
world's largest cactus. Cardon replaces Saquaro in Baja (the Saquaro is only
found north of the border); they resemble one another, but Cardon has more, and
longer, arms.
Contrary to popular
myth, cacti are not an efficient source of water for lost souls dying of thirst
in the desert. Barrel cacti, for example, do not give water, but an astringent,
unpalatable greenish-yellow jelly-like sap called mucilage. Any attempt to
drink this bitter alkaline fluid would likely result in vomiting and
dehydration.
 The "jumping" cholla is the pit bull of the cactus
world. It's thickly covered with long, barbed spines that pierce skin at the
slightest pressure and hold fast. Cholla segments separate easily from their
parent plant, leaving the unfortunate hiker firmly attached to something
resembling a rabid sea urchin. Attempting to pluck off a spine-covered cholla
segment with your fingers merely results in stabbed digits. The best strategy
is to use a stick, fork or comb. Insert the tines between skin and cholla, and
pull gently outward. Most individual spines can be removed using tweezers or
needle-nose pliers.
The agave is commonly
called the century plant because it was generally believed that it took 100
years for a plant to mature, after which it would bloom and then die. This is
an intriguing idea, but it's not true. Some agaves do follow the general
pattern of dying after they have flowered. Their lives however, only span a
period of eight to twenty years. Agaves have played an important role in the
human economy from ancient times as a source of food, drink, and fiber.
Alcoholic drinks such as mescal and tequila are a product of this
plant.
Resembling a bonsai
tree, the Elephant Tree or Torote is distinguished by its thick, enlarged trunk
and its butterscotch-yellow papery bark. Ranch women utilized the fruits from
this tangerine-scented tree as a perfume.
A most unusual plant,
the Ocotillo has no main truck, but instead, many whip-like branches which
spread fan-like from the base. Following a rain, scarlet tubular flowers bloom
and offer a popular nectar to hummingbirds. During periods of drought, ocotillo
will lose its leaves to prevent water loss to evaporation.
Palo Verde trees are
among the most conspicuous and characteristic plants of the Sonoran Desert.
They have smooth, greenish bark and twigs armed with long spines. The palo
verde trees' small leaves can turn to catch or avoid the sunlight and, like the
ocotillo, are drought-deciduous. In spring, a profusion of small yellow flowers
sprinkle the ground and give the tree a festive aura.
Near the Pacific coast,
many large cacti are covered with a Ball Moss, much as one would expect in a
more tropical environment. This is due to the presence of humid Pacific Ocean
air, which these plants use as a water source.
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