Part 3

Shreve groups desert plants into three categories based on the manner in which they have contrived to conquer the hazards of desert life.

These are:

1. Drought-escaping plants; 2. Drought-evading plants; 3. Drought-resisting plants.

Drought-escaping plants are the “desert quickies,” or ephemerals. Taking advantage of the two seasons of rainfall on the desert (midsummer showers and midwinter soakers) they develop rapidly, blossom, and mature their seeds which lie dormant in the soil during the rest of the year, thus escaping the season of heat and drought. There are two groups of these “quickies,” the summer ephemerals and the winter ephemerals. The former are hot-weather plants; the latter are species that thrive during the cool, moist weather of winter and early spring. These “quickies” present their spectacular floral displays only following seasons of above-average precipitation.

Drought-evading plants (in common with the deciduous plants of northern and colder climes which remain dormant while below-freezing temperatures prevail), meet the heat and drought by reducing the bodily processes to maintain life only, dropping their leaves, and remaining in a state of dormancy until temperature and moisture conditions, suitable to renewed activity, again prevail.

The drought-resisting plants are the bold spirits which take the worst that the desert has to offer without flinching, or resorting to evasive tactics. Chief among these are the cacti which store moisture in their spongy stem or root tissues during periods of rainfall, using it sparingly during drought. To reduce moisture loss to a minimum, they have done away with their leaves, the green skin of their stems taking over the function of foliage. Other plants, such as the Mesquite, develop deep or widespread root systems that extract every drop of moisture from a huge area of soil. The majority of the drought-resisters either cut down their leaf surface to an irreducible minimum, or coat the leaves with wax or varnish, thus restricting the loss of moisture.

Methods, techniques, devices, or body modifications which desert plants have developed or evolved to enable them to withstand the rigors of long-continued drought and heat are legion. Many of them are known and understood, but it is probable that there are many others which scientists have not yet discovered.

ACKNOWLEDGMENTS

For numerous helpful suggestions, lists of common flowers, herbarium and fresh specimens for use in preparing illustrations, and for assistance in many other ways, the author and illustrator proffer sincere thanks to the following: Glen Bean, L. Floyd Keller, Walter B. McDougall, and William R. Supernaugh of the National Park Service; Dr. Norman C. Cooper, research associate, Allen Hancock Foundation; Mrs. Robert Gibbs, Isle Royale National Park, Mich.; Leslie M. Goodding, St. David, Arizona; Edmund C. Jaeger, Riverside Junior College, California; Thomas H. Kearney, California Academy of Sciences; Robert H. Peebles (who kindly reviewed the manuscript), director of the U. S. Field Service Station, Department of Agriculture, Sacaton, Arizona; Paul Ricker, president, Wildflower Preservation Society, Washington, D. C.; and Barton H. Warnock, head of biology department, Sul Ross State College, Alpine, Texas.

Common Names: GIANT CACTUS, (SAGUARO) Arizona desert. (Carnegiea gigantea). Waxy white. May-June. Cactus family. Size: Up to 50 feet tall and 12 tons in weight.

Largest of the U. S. cacti, this species occurs only in southern and western Arizona and adjoining northwestern Mexico and sparingly in extreme southeast California. It is an indicator of the Sonoran Desert.

This giant is such a spectacular example of desert vegetation that it is used as a trademark of the desert. It is the state flower of Arizona. Blossoms unfold at night, remaining open until late the following afternoon, attracting swarms of insects which in turn attract birds. Fruits mature in July, resembling small, egg-shaped cucumbers. When ripe, they burst open revealing a scarlet lining and deep red pulp filled with tiny black seeds. Fruits are eagerly sought by birds and rodents.

Because of its enormous capacity for storing water in its spongy stem tissue, the Saguaro (sah-WAR-oh) produces flowers and fruits even during droughts of long duration. When other foods failed, the Pima and Papago Indians could depend upon the Saguaro harvest.

Saguaros are believed to live to a maximum age of 200 years, usually succumbing to a necrosis disease transmitted by the larvæ of a small moth. Grazing cattle trample out the young plants and much of the desert occupied by Saguaros is being placed under cultivation. Both Saguaro National Monument and Organ Pipe Cactus National Monument preserve and protect spectacular stands of these desert behemoths.

WHITE

Common Names: NIGHTBLOOMING CEREUS, (Reina-de-la-noche) Arizona and Texas deserts. (Peniocereus greggi). White. June-July. Cactus family. Size: 2 to 5 feet tall.

One of the most delicately beautiful of the flowers for which the desert is famous, “Queen of the Night” is waxy-white with thread-like stamens that give it the appearance of wearing a halo. The night on which the Cereus blooms is eagerly awaited by desert dwellers of long residence. All of the buds on a single plant, from two to six or seven in number, may open on the same night or may time their opening over a period of a week or more, usually in late June or early July, depending upon the season and other factors.

It is not unusual for nearly all of the plants in one locality to blossom on the same night. Buds unfold in the early evening, the flowers wilting permanently soon after sunrise the following morning. Fragrant, with a heavy, cloying perfume, they attract large numbers of night-flying insects.

The long, slender, fluted, lead-colored stems of the Nightblooming Cereus are inconspicuous and unattractive. Usually growing upward from beneath a Creosotebush or other desert shrub, they are partially supported and almost entirely hidden by the larger plant.

The beet-like root, which serves as a moisture-storage organ, may weigh from 5 to 85 pounds and is reportedly eaten by desert Indians. Fruits are podlike, pointed at the ends, and the size of a large pickle. They turn dull red when mature.

WHITE

Common Names: WESTERN-JIMSON, THORNAPPLE, GIANT-JIMSON, SACRED DATURA Arizona, California, and Texas deserts. (Datura meteloides). White. May-October. Potato family. Size: Up to 3 feet tall, and spreading over as much as 50 square feet of ground.

All portions of this coarse, vine-like herb are poisonous, and are used by some Indians as a narcotic to induce visions.

Seeds are sometimes administered to prevent miscarriage.

The plants with their large, gray-green leaves and showy, white, sometimes lavender-tinted flowers which open at night and close soon after contact by rays of the morning sun, are a common and arresting sight along roadsides and washes at elevations from 1,000 to 6,500 feet in Texas, New Mexico, southern Utah, southern California, and Mexico.

WHITE

Common Names: PRICKLYPOPPY, THISTLEPOPPY, (CHICALOTE) Arizona, California, and Texas deserts. (Argemone platyceras). White. Blooms all year. Poppy family. Size: Up to 30 inches in height.

One of the commonest and most noticeable perennials of the Southwest, the Pricklypoppy ranges from South Dakota and Wyoming to Texas, Arizona, southern California, and northern Mexico. A coarse, prickly plant with large flowers and yellowish sap, it is easily recognized.