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  • Tucson Mountain District Roads Closed Due to Flash Flooding

    Several interior roads, including the scenic loop, are closed in Tucson Mountain District (west) due to severe storms and flash flooding on August 26th. Roads will remain closed until further notice. Check the park's facebook page for updated information More »

  • Labor Day Run - Rincon Mountain District Road Closure - Sept. 1st

    Due to the Annual Labor Day Run, Saguaro National Park's Rincon Mountain District Loop Drive will be closed from 4:00am to approx 10:30am on Sept. 1, 2014. Please be advised of vehicle congestion along roadsides when approaching the park during this time. More »

Why saguaros have pleats

The saturated desert floor can become very soft after a heavy rainstorm, sometimes making it difficult for a heavy saguaro to remain standing in the wind.

Wide reaching, but shallow roots can lead to saguaro blowover

L. Bolyard

The roots of a saguaro grow out from the plant in a radial fashion, several inches under the ground. During a heavy rain, a saguaro will absorb as much water as its root system allows.
The flesh of a saguaro cactus is spongy, thready, and similar to tough squash.

The flesh of the saguaro cactus is located just beneath the tough green skin.

L. Bolyard

To accomodate this potentially large influx of water, the pleats allow the flesh to soak up water, expanding like an accordion. Conversely, when the desert is dry, the saguaro uses its stored water and the pleats contract.
Saguaro cactus skeleton showing through tear where arm broke off.

A bloated saguaro's arm became too heavy after a rainstorm and the following high winds, leaving the woody skeleton of the saguaro cactus visible through the exposed flesh.

L. Bolyard

Because the majority of a saguaro is made up of water, an adult plant may weigh 6 tons or more. This tremendous weight is supported by a circular skeleton of inter-connected, woody ribs. The number of ribs inside the plant correspond to the number of pleats on the outside of the plant. As the saguaro grows, the ribs will occasionally fork and the corresponding pleat will also fork at the same place.

Sometimes saguaros have the chance to soak up a larger than usual amount of water - such as after a large summer rainstorm. The ground can become very soft after such a storm and with the added weight of the new water, the heavy cactus sometimes fall over or lose an arm.

Saguaro cactus ribs protruding out of broken saguaro that fell after a monsoon storm.

A look inside a broken saguaro reveals the different layers of the cactus.

L. Bolyard

Layers of a saguaro:

protective spines

epidermis (green part)

cortex or pulp

ribs (with corresponding pleat on surface)

pith (inside the ribs)

Did You Know?

Gila Monster

Gila monsters are one of two venomous lizards in the world. The other is the similar Mexican beaded lizard. Gila monster venom evolved as a defensive rather than offensive weapon.