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Description

The many, usually unbranched stems that arise from ground level readily distinguish an organpipe cactus from a saguaro. The stems also are thinner, and have solid woody cores. Plants are usually 9 to 11 feet (2.7-3.4 m) in height, but occasionally exceed 20 feet (6.1 m). The pinkish-white flowers, produced from April through August, open after dark and close shortly after sunrise. The spines on the fruit loosen and fall at ripeness. The juicy, sweet, red pulp contains many tiny seeds.

Range

In Arizona the organpipe cactus is found mostly in Organ Pipe Cactus National Monument and the adjacent Tohono O'odham Indian Reservation in the south-central part of the state. In Mexico it occurs almost throughout Sonora, the southern half of Baja California, and barely extends into Chihuahua and Sinaloa. The desert is marginal habitat for this species; it is more abundant in thornscrub and tropical deciduous forest.

Notes

This tropical cactus is more frost sensitive than the saguaro, so it is restricted to the warmest microhabitats at its northern limit in the United States. It is most often found on south-facing rocky slopes below 3300 feet (1000 m) in elevation.

Nectar-feeding bats are the primary pollinators and some of the major seed disperses. Because the flowers close at daybreak, diurnal animals are not significant pollinators as they are of saguaros.

The fruits of organpipe cactus are widely regarded as the second-best-tasting fruit of all cacti (after those of Stenocereus gummosus). Commercial harvest is feasible in some large populations, and fruits are sold in markets in Sonora and Baja California.

Organpipe is the dominant plant in a strip of thornscrub several miles wide along the coast of southern Sonora; they grow so densely that visibility is seldom more than a few yards (meters), and with the other thorny vegetation they form nearly impenetrable thickets.

The ribs are used in housing. The Seri made boat sealant from dried organpipe flesh and animal fat. Slabs of heated organpipe flesh were used as compresses for aches.

Two defining life forms of the Sonoran Desert's vegetation are giant columnar cacti and legume trees.

Both are characteristic of arid tropical habitats (the cacti only in the "New World") and their presence in the Sonoran Desert reflects its affinity to the tropics. Arizona Upland (a sub-division of the Sonoran Desert) experiences frequent frosts, and only one columnar cactus (the saguaro) is sufficiently cold-hardy to be widespread in this subdivision. The Lower Colorado River Valley subdivision is too dry for columnar cacti and they are almost absent there. Several species of giant columnar cacti occur in each of the other four subdivisions.

In addition to the giants described below, there are several smaller columnar species in the Sonoran Desert, and even more small and large species in the adjacent tropical communities. Myrtillocactus cochal (cochal) occurs in Baja California. It branches profusely from a short trunk, forming a large candelabra-shaped mass of stems up to 13 feet (4 m) tall and wide. Repeat photography indicates that it lives only a few decades. Bergerocactus emoryi (golden torch cactus), also from Baja California, has very slender stems to about 7 feet (2 m) tall densely clothed with yellow spines. Pachycereus pecten-aboriginum (etcho, hecho, cardón barbón) resembles a skinny cardón. Its fruit is very bristly and used as a hair brush. It is mainly a thornscrub species that enters the southern edge of the Sonoran Desert in southern Sonora and southern Baja California.

The enormous popularity of cacti among gardeners and plant collectors is surpassed only by that of roses and orchids. Their appeal extends far beyond their native habitat; there are legions of devotees in the eastern United States, Europe, and Japan. The desire to possess these strange yet beautiful plants supports hundreds of specialty nurseries; the largest shops grow and sell millions of plants annually. Cacti are one of the reasons tourists visit the American southwest.

Description of Family

Most people think they know a cactus when they see one, but they are often mistaken. All cacti are succulents, but not all succulents are cacti. Agaves, ocotillos, aloes, and the succulent euphorbias (such as African milk trees) are among the swollen or spiny plants often mistaken for cacti. However, the term cactus refers to a particular family of plants defined by a distinctive flower pattern. To be a cactus, the plant must produce flowers with the following characteristics: many tepals (combined sepals and petals) that intergrade with each other; many stamens (usually hundreds), and numerous stigma lobes (rarely only three). If a plant lacks such a flower, it cannot be a cactus.

Range

The cactus family is nearly endemic to the New World from southern Canada to southern South America. There is an exception — one of the 1800 species occurs naturally in Africa, Sri Lanka, and Madagascar. However, introduced cacti have gone wild and sometimes become pests in several regions of the Old World. Cacti are most common (in numbers of both plants and species) in semiarid habitats with low rainfall, yet with dependable rainy seasons. A few species occur in extremely arid deserts and wet tropical forests. About 300 species occur in the Sonoran Desert region.

Notes

The majority of cactus species are pollinated by numerous species of bees, a number of which specialize in cacti. Cactus bees are all solitary, but in some species the females congregate by hundreds of thousands at nesting sites to dig their individual nest burrows, which are densely concentrated in an area of a few thousand square feet. Cactus pollen is packed into these burrows to feed the grubs, which the parents do not tend. Some cacti are pollinated by birds, moths, or bats.