One of the first areas you will want to visit in Big Bend is the Dagger
Flats Auto Trail. This is a narrow and winding gravel road seven miles
long that ends in a "forest" of Yucca faxoniana (syn. =
Y. carnerosana), the Giant Dagger Yucca. One of the major attractions
of this route is that you can see a number of the Yucca species in the
park in a fairly short period of time, in addition to other interesting
plants. You can--and should--pick up a guide published by the Big Bend
Natural History Assocation at the beginning of the route. It provides an
excellent description of the plants and terrain. This virtual field trip
largely follows that guide and you can use it to find all these plants
and others on this route.
Agave lechuguilla
A common plant in the Chihuhuan Desert is Agave lechuguilla (Lechuguilla).
It is a member of the Agavaceae
(Agave Family) and like other members of this family, blooms once after
a long period of growth, sets seeds, and dies. The middle image is a flower
cluster or inflorescence of Lechuguilla flowers, a spike 2-3 meters long.
This plant is eaten by deer. They can't eat the spiny leaves, but rip them
off and eat the succulent base of the plant. It is not unusual to find
Lechuguilla leaves scattered around where deer have been browsing. You
can find this plant in many other areas of the park. The deer was on a
trail in the Chisos Mountains.
Larrea tridentata
You will also encounter Larrea tridentata (Creosote bush), another
very successful and common desert plant and a member of the Zygophyllaceae
or Caltrop family. It has very small, split leaves, yellow flowers and
a pubescent (fuzzy) white fruit. It is also aromatic, which indicates the
presence of terpenoids (volatile oils). The common name of Creosote bush
is due to the smell of these compounds. Terpenoids are long chain hydrocarbons
and are found in a large number of plants. They protect the plants from
herbivores and, in some cases, prevent other plants from growing in the
vicinity (allelopathy). They are probably also the basis for the medicinal
use of Creosote bush lotion as an antiseptic. The Creosote bushes you are
looking at in the desert may be very old--clones estimated at 11,700 years
of age have been found in the Mojave desert.
Fouquieria splendens
Fouquieria splendens (Ocotillo) is one of the more interesting
and spectacular plants in Big Bend. It is a member of the
Fouquieriaceae
or Fouquieria family and is in the only genus in the family. It conserves
water by dropping its leaves and going dormant in dry weather. After a
rain, Ocotillo produces new leaves. It can serve as an indicator of whether
or not an area has recently received rain. The source of much of the rainfall
for Big Bend is spotty thunderstorms, so you can see Ocotillo in both dormant
and growing states in different areas of the park. The spines are more
obvious on the dormant plants.
The plants apparently are not dependent on recent rainfall to flower
and fruit. The striking crimson red flowers appear in the spring and the
fruits are capsules. The fruits are often bright red and you may mistake
them for flowers unless you take a close look.
Echinocereus stramineus
This large clump is Echinocereus stramineus (Strawberry Pitaya),
a member of the Cactaceae
(Cactus Family). As with most cacti, the leaves have been reduced to spines
which function to protect the plant from herbivores. They may also reflect
sunlight and radiate heat away from the plant. Unfortunately, we were too
early to catch this plant in flower.
Old Ore Road branches off Dagger Flats Road. You should not attempt
this drive unless you have a high clearance, preferably 4-wheel drive vehicle
and have informed someone that you are going to be travelling on this road.
It is a long, hot walk back to the main road.
Diospyros texana
Diospyros texana (Texas Persimmon) occurs in slightly wetter
areas, such as the slopes of the dry washes. It is a member of the Ebenaceae
(Ebony or Persimmon family). This plant is dioecious, which means that
the flowers are unisexual and occur on separate plants. Thus, the plants
can be described as either male or female. Obviously, fruits only develop
on female plants. The images below are of female flowers and the fruits.
The fruits are eaten by wildlife but are incredibly astringent. You will
be puckered up for several days, maybe permanently, if you taste one of
these when it is unripe. It is better to leave them for the permanent inhabitants
of the desert.
Yucca torreyi
Yucca torreyii (Torrey Yucca) is the first species of Yucca
that
you will encounter on this road. This particular species is the most common
one in Big Bend. It is a member of the
Agavaceae
Dasylirion leiophyllum
At this point you are about 400 feet higher in elevation than at the
beginning of the road, and the vegetation is changing due to the presence
of more rainfall at the higher elevations. Dasylirion leiophyllum
(Sotol) is found at middle elevations in Big Bend. It is also a member
of the Agavaceae.
The leaves are used for thatching and baskets and the leaf bases ("spoons")
are used in floral arrangements. The trunks are roasted, fermented, and
distilled to produce an alcoholic beverage (sotol).
Yucca elata
Yucca elata (Soaptree Yucca) received its common name from a
fluid it contains that native Americans used as soap. It is the tallest
Yucca
in the park. The leaves are narrow relative to those of the other Yuccas.
Juniperus pinchotii
Juniperus pinchotii (Red-berry Juniper) is a plant out of place
in this part of park. It is usually found at the wetter, higher elevations.
It is a member of the Cupressaceae.
It may be a remnant from a time when the climate at Big Bend was moister
and cooler. In any case, it is easy to spot. Notice the
Yucca growing
behind it.
Yucca faxoniana
Yucca faxoniana (Giant Dagger Yucca) is one of the high points
(and there are many pointy things in Big Bend) of the Dagger Flats excursion.
You will probably have to go to this area to see this particular Yucca
because it is rare in the rest of Big Bend. There is a "forest" of these
near the turn-around. The plants are very impressive, having large, thick
leaves.
Yucca thompsoniana
Yucca thompsoniana (syn. =Y. rostrata) is also found in
this area. It has a narrow leaf like Yucca elata (Soaptree Yucca),
but the leaf margins of Yucca rostrata are serrated, rather than
having the fibers found on Soaptree Yucca.
This is the end of the auto trail. If you visit Big Bend, don't be
a weenie, take some time to get out of your car and look around. There
is always something interesting going on in the desert that you can't see
from a car. Some good advice for looking around the desert: take plenty
of water, wear a hat and sunglasses, keep your eyes and ears open (turn
off the radio), and don't back up without looking behind you.
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