A word or two about the slow-growing saguaro cactus, Carnegiea gigantea (Cerus giganteus):
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1 year 3 years 5 years 15 years 50 years 70+ years
(You should see the REALLY old, five-armed ones.)
The saguaro cactus usually begins life under another tree or shrub, often a palo verde, mesquite, or creosote. These nurse plants provide a microhabitat for the cactus, protecting and sheltering it, providing a moister and more shaded environment in which it can flourish.
Given the great weight (over a ton) and height (up to 50 feet), of the adult plant, the saguaro’s root system is surprisingly shallow. The tap root is a pad about three feet in length; other sturdy roots radiate from the base in all directions, no more than a foot underground. Smaller roots grow just below the surface, wrapping around rocks as they go and extending out in all directions for a distance approximately equal to the height of the cactus.
The skin of the saguaro is fluted and waxy, and 2-inch spines cover the ribs. The outer pulp of the saguaro has the ability to expand like an accordion, increasing the diameter of the stem in order to hold more water. The saguaro blooms each year, no matter how arid the conditions. Its creamy white flowers with yellow stamens appear on the tops of the trunk and stems over the course of 30-40 days. Flowers bloom at night, and close by noon the following day. If fertilized (by cross pollination, with the help of insects, bats and birds), the green fruit of the saguaro begins to form right away. The fruit matures just before monsoon season: it ripens and splits, revealing bright red, pulpy flesh attractive to many desert creatures, including humans. Native Americans living in the area considered the saguaro fruit to be an important food source, and found uses for the seeds, flesh, and juice.
Sources:
A.R. Royo, Sagauro Cactus, http://www.desertusa.com/july96/du_saguaro.html 5/22/02
exhibit at the Arizona-Sonora Desert Museum, 5/16/02
http://www.desertusa.com/mag01/aug/papr/palov.html 5/23/02
See also Lometa’s excellent writeup under Giant Saguaro.