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[suh gwah' rO] (Carnegiea gigantea) the largest cactus of the United States


The saguaro grows only in the foothills and deserts of southern Arizona, southeastern California, and northwestern Mexico. Within its range, however, it can be extremely abundant, forming thick forests among other desert trees and shrubs.

The largest cactus native to the United States, the saguaro has a columnlike trunk that measures from 1 to 2 feet in diameter, stands up to 50 feet tall, and weighs as much as 10 short tons. It also has a few large, upturned branches. Grooves and ribs run lengthwise along both the trunk and branches. Because little rain falls in the region where saguaros grow, the plant must soak up and store large amounts of water after the rare showers that do occur. The grooves and ribs expand and contract depending on the amount of stored water.

Padlike structures called areoles grow along the ribs. Each areole has from 15 to 25 long spines. During May and June, the areoles near the tip of the trunk and branches produce waxy, greenish-white flowers. Each funnel-shaped flower measures 3 to 4 inches long, and blooms at night.

close-up of the Saguaro showing flowers and buds

Bats, birds, and insects gather nectar from saguaro blossoms and, during the process, spread pollen from flower to flower. The pollinated flowers may then produce purplish-red, egg-shaped fruit. Many desert creatures eat this fruit.

Saguaros also provide habitat for several animals. The most conspicuous of these is the Gila woodpecker, which creates many of the nest holes seen in mature saguaro stems.

One of the longest-living plants in the world, saguaros commonly live 200 years or more.

The flower of the Saguaro cactus is the State Flower of Arizona.

Scientific Classification

division Magnoliophyta
class Magnoliopsida
subclass Caryophyllidae
order Caryophyllales
family Cactaceae
subfamily Cactoideae

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The Robinson Library >> Family Cactaceae

This page was last updated on August 31, 2018.