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How big is a Saguaro Cactus?

6 meters!

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Saguaro Cactus

The saguaro (pronounced sa-WAH-ro) is a giant cactus that grows almost entirely in the Sonoran Desert, in southern Arizona, the southeastern corner of California and western Sonora, Mexico. The saguaro shown here is 6 meters (20 feet) tall, measured from the ground to its top. In the wetter parts of the desert, a saguaro reaches that height at about 100 years old, and many keep growing to about 10 meters (33 feet).

Size

A saguaro's size is given as its height. The U.S. Forest Service describes saguaros as commonly reaching 10 meters tall and sometimes 15 meters (49 feet). The National Park Service also says an adult can be as tall as 50 feet (15 meters). The main stem of a mature plant is 30–60 centimeters (12–24 inches) across.

Height depends on age and, above all, on water. In the wetter eastern part of the Sonoran Desert, saguaros about 100 years old average 5.8–8 meters (19–26 feet) tall, depending on the site. In the drier west, plants of the same age average only about 4.5 meters (15 feet).

Scientists usually estimate a saguaro's age from its height. Because growth rates differ from place to place, they use rates measured at the same site as the plant being aged.

Size comparisons

  • A 6-meter saguaro is about three and a half times as tall as a person 1.7 meters (5 feet 7 inches) tall.
  • It is about twice as tall as a basketball hoop, whose rim is 3.05 meters (10 feet) above the floor.
  • The Apollo Lunar Module stood 7.0 meters (22 feet 11 inches) tall on its landing legs, about 1 meter taller than this saguaro.
  • As of 2026, the tallest saguaro on record stood 78 feet (23.8 meters) tall before it fell in 1986. It was about four times as tall as the one shown here.

How a saguaro grows

A young saguaro usually starts life in the shade of a nurse tree, such as a palo verde, ironwood or mesquite, which protects it from summer sun and winter frost. It grows very slowly at first. On some sites, a saguaro takes up to 50 years to reach 1 meter (3.3 feet) tall.

Growth then speeds up, to 5–10 centimeters (2–4 inches) a year. Most saguaros begin to flower and fruit at about 2 meters (6.6 feet) tall, when they are 30–50 years old. Arms usually appear once the stem is 3.75–5 meters (12–16 feet) tall. In Saguaro National Park that happens at 60–75 years of age, but in drier places it can take up to 100 years.

Some saguaros never grow arms at all. Saguaros typically live 150–200 years, and the oldest known one was estimated to be nearly 300 years old.

Water and weight

Most of a saguaro's weight is water. Large plants are estimated to weigh 3,000–4,000 kilograms (6,600–8,800 pounds), and 85–90% of that is water. The roots spread out sideways only a few centimeters (several inches) below the ground. During a heavy rain, the plant takes up as much water as its roots allow.

The pleats that run down the stem open out like an accordion to hold the extra water, and close up again as the plant uses it during dry spells. Inside, a ring of woody ribs holds up the weight, with one rib for each pleat on the outside.

Sources

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