Carnegiea

The spectacular stands of the giant saguaro in many parts of Arizona have been the subject of countless photographs and essays. I thoroughly enjoy looking out my window at the Desert Botanical Garden and seeing several handsome sa-guaros. Indeed, Carnegiea is one of the most popular cacti, not only in greenhouse collections but also in desert landscaping and outdoor gardens. The cactus has also been extensively studied with regard to ecology, growth dynamics, and reproduction.

George Engelmann had the privilege of first describing the saguaro in 1848, from collections made during the boundary survey led by William H. Emory, during which many new cacti were found. Engelmann named it Cereus giganteus. Sixty years later Nathaniel Britton and Joseph Rose described a new genus for the saguaro, Carnegiea (type, Cereus giganteus = Carnegiea gigantea), the name honoring the great philanthropist, Andrew Carnegie. Most botanists, with the exception of Lyman Benson (1982), have followed Britton and Rose, accepting it as a distinct genus of one species. The International Cactaceae Systematics Group agonized over what to do with Carnegiea and those plants closely related to it. Studies by Arthur Gibson and Karl Horak (1978) show that Carnegiea is closely related to Neobuxbaumia, so in its first consensus publication (Hunt and Taylor 1986) the group tentatively placed 12 species from probable closely related genera in Carnegiea. However, Gibson and others felt that it would be best to retain the two genera, which the group has done in succeeding treatments (Hunt and Taylor 1990).

Carnegiea gigantea continues to be of importance to Native Americans (see Chapter 2, under Saguaro, Cacti as Medicine, and Other Uses of Cacti). It flowers in late spring with the flowers open both day and night, pollinated by birds, bees, and bats.

Carnegiea Britton & Rose 1908

Subfamily Cactoideae, tribe Pachycereeae.

Calymmanthium substerile, photograph by Jean-Marie Solichon

1 38 Carnegiea gigantea

1 38 Carnegiea gigantea

Carnegiea gigantea, also illustrated on pages 1,25, and 74; fruits illustrated on page 50

Carnegiea gigantea (Engelmann) Britton &Rose 1908

saguaro or sahuaro, and giant cactus, sage of the desert

Cereus giganteus Engelmann 1848, Pilocereus giganteus (Engelmann) Rumpler 1885

Plants large, treelike, columnar, branching well above the ground, to 16 m (52 ft) high. Stems green, cylindrical, 30-75 cm (12-30 in) in diameter. Ribs 12-30, vertical, prominent. Areoles numerous, closely spaced. Spines 15-30, in dense clusters along the ribs, gray to blackish, diverging, straight, 2.5-3.8 cm (1-1.5 in) long. Flowers borne just below the stem tips, open during the day and night, funnelform to bell shaped, white, 8.5-12.5 cm (3.3-4.9 in) long, 5-6 cm (2-2.4 in) in diameter; pericarpels and floral tubes long, covered with many distinct scales, extending down and clasping, and felted areoles. Fruits obovoid, red, fleshy at maturity, edible, 5-7.5 cm (2-3 in) long, 2.5-4.4 cm (1-1.7 in) in diameter, with scales, dehiscent along three or four vertical lines, exposing the red interior. Seeds black, 2 mm long, obovoid. Distribution: Sonoran Desert, primarily in Arizona and in southern California just west of the Colorado River, south into Sonora, Mexico, at elevations of 180-1350 m (590-4430 ft). Carnegiea gigantea is not listed as endangered or threatened, but Arizona has strict regulations regarding the harvesting or selling of saguaros. Permits must be obtained from the state, even for salvage operations. Urban development near Phoenix and Tucson has affected populations of C. gigantea gravely, but developers are now required to salvage or protect saguaros that may be threatened by their operations.

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