Saguaro National Monument

The Saguaro National Monument is named for just one type of cactus which grows in both parts of this two-section monument, the saguaro (sah-WAH-roe) cactus.

This giant cactus matures very slowly, taking about 25 years to grow to just 2 feet. Youngsters need protection and shade. Arms don't appear until saguaro are about 75 years old. The old-timers live over 200 years and reach 50 feet.

Geology

Some 10 to 20 million years ago the earth's crust was stretched, the breaks and tears that resulted became fault-block mountains. Some were displaced 5,900 to 9,900 ft, and most turned northwest. The valleys in this area, are thought to have been formed more by a collapse of the basins than an uplift of the ranges, creating large bowls rimmed with mountains.

The basins filled with river-borne sediments. The fronts of the ranges retreated and the mountains literally began to fall down around themselves. Cone-shaped aprons of rock, sand and silt carried by streams down the steep slopes, spread out on the floor of the desert basin. These alluvial fans merged to form bajadas, which slope gently into the valley.

The rocks that composed the Tucson Mountains are frosted with a layer of fine grained rock called rhyolite tuff, which originated as ash flow from a volcanic eruption. Valuable minerals are often found where super-hot molten material contacts sedimentary rocks (limestones, sandstones, and shales) underground. This geological phenomenon brought a barrage of miners to these mountains in the 1880s, searching for gold, silver and later, copper.

Prehistoric and Historic Indians

At least 8,000 years ago humans lived in these mountains and valleys. Remnants of trails, some shrines, and sleeping circles, weathered rooms of stream cobble, and tools chipped form stone are about all that is left. Petroglyphs, like those pecked into the rock near the Signal Hill Picnic Area, are a trace of artistic expression or some form of communication. Archaeologists are not sure.

From 300 BC on, the story becomes a bit clearer. Archaeologists have studied the people who built extensive irrigation systems in the desert. They call them the Hohokam. Their artifacts - etched shells, copper mirrors, and large ballcourts - intrigue most historians. They obtained corn and then beans from Mexico. Tending their fields, they also cultivated hundreds of edible plants in the Sonoran Desert.

They are probably the ancestors of the Papago, who in 1898, were still migrating from their more-or-less permanent winter rancherias to summer fields constructed at the mouths of arroyos.

Historical Background

In the late nineteenth century the Southern Pacific Railroad came to the dusty frontier town of Tucson. Miners, homesteaders, and a steady influx of people meant long-lasting changes for the desert. The Depression years were critical ones for the land that would become Saguaro National Monument, Tucson Mountains Unit. Local citizens began taking steps to preserve some of the land for wildlife and in 1929 acreage was withdrawn from homesteading and mining to become the Tucson Mountain Park. President Franklin Roosevelt's "Tree Army," the Civilian Conservation Corps., constructed solid masonry buildings in the 1930s that can still be seen throughout the park.

In 1959 attempts to open the park to exploration by copper mining companies met strong opposition from citizens, who by then were living in a large city. The intrisict value of untouched land had become too fret. Pressure to reopen the area to mineral entry spurred the U.S. Congress to designate 15,360 ares as the Tucson Mountain Unit of the existing Saguaro National Monument. President John F. Kennedy signed the proclamation on November 15, 1961. Later the unit's authorized boundaries were expanded to 21,000 acres.

The Saguaro Cactus

To the Papago Indians, whose homeland has always been the Sonoran Desert, the saguaro is an Indian. To harm it is to harm one's brother or sister. The Papago calendar revolves around the saguaro. June, New Year's, is the month of the seed blackening. This is where it begins. Thousands of tiny seed inside the ripe fruit area ready to be scattered. As the fruit falls from the top of a fifty-foot saguaro, doves, ants, and ground squirrels move in for the harvest. The Papago, too, formerly gathered great quantities of the fruit by knocking it down from the saguaro with poles. They made saguaro wine for their rain ceremonies and are the seeds like candy.

Of the billions of seeds produced by saguaros each year, only a small percentage will become seedlings. Special conditions of moisture and temperature are necessary for germination. Only after shallowly buried seeds have received a good drenching from the summer monsoons in July and August will they emerge as seedlings.

The average life expectancy of a newly sprouted seedling is under six weeks. Less than a quarter inch high, it is vulnerable to insects and rodents. Should this vulnerable new plant survive all the obstacles of predation, freezing and drought, it has a chance to grow to adulthood.

In ten or fifteen years a juvenile plant may be recognizable as a saguaro. By this time it may be three feet tall. Its growth spurts coincide with the summer rains, as it builds water storage tissue and develops a wide-spread root system.

At about age thirty, approximately 6 feet tall, a saguaro's reproductive life begins. The already slow growth declines even more as the cactus devotes more energy to producing buds, flowers and fruit. Blossoms appear in late May and early June. At night, when the flowers are open, a long-nosed bat pokes its head in to feed on the pollen.

When mature, a saguaro may reach thirty of forty feet in height. One washed down in a rain in the Santa Catalina Mountains north of Tucson weighed in at nine tons. To support this mass is a root system that is not deep (rarely more than 3 ft down) but that may extend up to 100 ft out from the cactus. The anchorage these lateral roots supply is essential to a saguaro that would withstand powerful winds and erosion at its base. The strong woody skeleton that runs the length of the saguaro's stem also provides support.

Driving Tour

Red Hills Information Center has a few exhibits, brochures, books, and maps.