Carnegiea (2017)

By Eric Driskill (January 2017)

In 1848, George Engelmann described the saguaro with the name Cereus giganteus. A saguaro seedling germinated that same year might have only reached a height of just over 2 feet by the time Nathaniel Britton and Joseph Rose described a new genus for the saguaro, Carnegiea, 60 years later in 1908. The genus name honored Andrew Carnegie.

With their upward-reaching arms, carnegieas are an iconic image of the Southwest. People all over the world may have thought saguaros occupied most of America, if older Western films were the only exposure they had of our country. The plants are actually limited to the Sonoran Desert, primarily in Arizona, west of the Colorado River in southern California and south into Sonora, Mexico. Saguaros can be found from sea level to elevations of up to 4,000 feet.

The few plants growing above 4,000 feet are usually found on south-facing slopes, where freezing is less likely. Saguaro National Park in Arizona was designated in 1994 to help protect the plants and their habitat. This is the only U.S. national park dedicated to a particular plant species.

Carnegiea is a monotypic genus with gigantea being the only species. The plants become large and columnar, sometimes branching 10 to 50 feet off the ground after 50 to 100 years. Stems are green and cylindrical, up to 30 inches in diameter and ribbed with 12 to 30 ribs. Areoles are closely spaced with spines from 15 to 30 inches.

Carnegieas begin to flower after about 35 years of age and continue to flower throughout the life of the plants. The flowers are white and appear just below the stem tips. Flowers open late in the evening and remain open until the following evening. Those flowers pollinated by birds, insects or bats within that time frame develop into fruits that contain up to 2,000 seeds. It is estimated that a typical saguaro can produce up to 40 million seeds within its lifetime.

The plants are very slow-growing. From germination, they may grow only 1 or 1.5 inches in the first eight to 10 years of growth. Beyond that time, growth depends largely on location and precipitation. Even under the best conditions, these plants certainly take their time.

Very small plants can be purchased readily. Larger plants are available, but can get rather expensive, particularly if you have them shipped. When ordering larger plants, use only reputable nurseries that have either grown plants from seed or can provide proof of permits that show plants were rescued.

Carnegiea fruits are harvested and used as food, as well as to make wine. Ribs from dead plants are used not only as fruit-harvesting poles, but also as roof beams. The Tohono O’odham tribe refers to the plants as humans and believes nothing should be done to hurt them.