Nature · Ferns, grasses & other plants

Saguaro

Columnar cactus · to about 15 m · lives 150–200 years

Carnegiea gigantea — Cactaceae

The saguaro is the giant columnar cactus of the Sonoran Desert and the emblem of the American West, though it grows only in Arizona, a corner of California and Sonora in Mexico. It is extremely slow: a saguaro may be fifty to seventy years old before it grows its first arm, and two hundred before it dies. Its pleated stem swells like an accordion as it takes up water after rain. The blossom is the state flower of Arizona, and the holes woodpeckers drill in it become homes for a queue of desert birds.

How to spot them

▸A single tall fluted column, often with a few thick arms curving upward from well up the trunk
▸Deep vertical pleats that visibly expand and contract with the water in the stem
▸Ring of waxy white flowers opening at the very top of the trunk and arms in May and June
▸Old nest holes drilled by woodpeckers, often occupied by owls
▸Sonoran Desert only — Arizona, south-east California and Sonora; it does not grow in the Mojave

How to know it

This giant columnar cactus may be fifty to seventy years old before it grows its first arm

The saguaro.

Its pleated stem works like an accordion, swelling as the plant takes up water after desert rain

The saguaro.

Its genus honours the Scottish-American steel magnate and philanthropist

The saguaro, Carnegiea gigantea, named for Andrew Carnegie.

Its blossom is the state flower of Arizona, although the cactus grows in only one desert

The saguaro — the Sonoran Desert.

Gila woodpeckers and gilded flickers drill nest holes in it, and the hardened linings survive the plant's death as 'boots'

The saguaro — elf owls and purple martins later move into the holes.

Its fruit is harvested each summer by the Tohono O'odham, whose calendar year begins with the harvest

The saguaro.

Despite being the emblem of every Hollywood Western, it grows in only one American desert and never in the Mojave

The saguaro.

Quick-fire facts

•Carnegiea gigantea is named after Andrew Carnegie; it is the only species in its genus
•Confined to the Sonoran Desert: Arizona, a small part of south-eastern California, and Sonora, Mexico
•Kew records the tallest living saguaro as over 10 m and more than 200 years old, and the tallest ever recorded as just under 25 m, which fell in a windstorm in 1986
•Arms typically do not appear until the plant is 50 to 70 years old or more, and some plants never grow any
•Kew notes that the saguaro flower is the state flower of Arizona
•Flowers open at night and close the following afternoon, pollinated by bats, bees and white-winged doves
•Nest holes drilled by Gila woodpeckers and gilded flickers are later used by elf owls, purple martins and others; the hardened cavity linings, 'saguaro boots', outlast the cactus
•The fruit is central to Tohono O'odham tradition, fermented into a ceremonial wine and marking the start of their year
•Protected by Arizona law; harming one is an offence, and Saguaro National Park near Tucson exists for it
•It has a shallow, wide root system plus one deep taproot, and a woody internal rib skeleton that stands after the flesh rots

Drill it — 7 cards

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Sources

Royal Botanic Gardens, Kew — Saguaro cactus — Carnegiea gigantea