Saguaro cactus

The desert giant with its arms raised

The saguaro is the cactus with 'arms' from the cartoons! It grows up to 15 metres, but very slowly: at 10 years old it's only 4 cm. Its first 'arm' appears at age 70! After rain a saguaro soaks up a tonne of water and expands like an accordion. Birds build nests inside it.

The saguaro (Carnegiea gigantea) grows only in the Sonoran Desert (Arizona, Mexico), reaching 12–15 m and living up to 200 years. Its ribbed trunk expands as it soaks up water — a cactus can weigh 2 tonnes, 90% of it water. Its roots are shallow but spread 30 m — collecting rain quickly. Its spines are modified leaves that give shade and reduce evaporation. It blooms at night and is pollinated by bats. Woodpeckers and owls nest inside its trunk. It is sacred to the Tohono O'odham people and the symbol of Arizona. Cutting one down is a crime.

Fun facts

• At 10 a saguaro is 4 cm tall; it grows its first arm at 70.
• A big saguaro weighs 2 tonnes — 90% of it water.
• In Arizona you can go to jail for cutting down a saguaro.