Crested Saguaro Cactus
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Crested Saguaro Cactus
  
(Carnegiea gigantea)
  
NORTHEAST OF OLD MAIN
  
31 This is noticeable for its crown-shaped top. Cresting appears in many species of unrelated plants and is little understood. The crest may be a lateral dividing of the growing tip.

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In Depth Carnegiea gigantea, Crested Saguaro Cactus
Location: NORTHEAST OF OLD MAIN
Family: Cactaceae
Distribution: common, central Arizona through southern Sonora, to 1100 m (3500 ft) in elevation
Habitat: rocky slopes, sometimes sandy flats
Habit: large columnar cactus
Flowering: primarily May
Natural History Notes: The saguaro is Arizona's largest columnar cactus, representing a growth form that is much more abundant and diverse in México. Many westerns have been filmed around Tucson; this, in addition to its appearance on many "Old West" products, has given the mistaken impression that saguaros are ubiquitous. The saguaro, however, is found only in the Sonoran Desert, from southern Sonora to central Arizona, where summer rains provide needed moisture at the peak of stem growth. The large, white, waxy flowers each last just 24 hours. At night, bats visit the flowers for the nectar and serve as pollinators; during the day many additional visitors transport pollen, including the white-winged dove. When ripe, the fruits burst wide open displaying the bright red pulp and multitudes of tiny black seeds. The pulp serves to attract animals, who then distribute the seeds. Young saguaros are often found associated with shrubs or trees; these plants may serve as 'nurse plants', shielding the tender cactus from the harsh sun or occasional frosts until it's large enough to withstand such pressures. Even when adult, however, a saguaro can become sunburned if transplanted with its north side facing south. A slow grower, the saguaro takes three decades to reach sexual maturity and can live up to 200 years. By the time it reaches 4-5 meters, the plant is 50-70 years old and is finally ready to start developing branches. Flickers and gila woodpeckers build their nests in the stems of the saguaros; these holes are then used by may other creatures for nest sites, including the rare pygmy owls. The cactus forms a thick tissue to surround the burrow, and, as long as there are few enough such holes, remains healthy. These burrows are called saguaro 'boots', and can be found lying on the desert floor long after the saguaro that made it is reduced to a pile of long wooden ribs.