Saguaro (Carnegiea gigantea) — identification, habitat & look-alikes

The saguaro is the iconic giant cactus of the Sonoran Desert and the largest cactus in the US, typically growing 10–52 ft (3–16 m) tall and living 150 to 200 years. It grows wild only in Arizona, a few spots in southeastern California, and Sonora, Mexico. Its white blossom is Arizona's state flower.

Appearance

Appearance: A large saguaro can top 50 ft (15 m) and 2 tons, mostly water. The pleated trunk swells to store rain and shrinks in drought, held up by woody ribs; shallow roots spread wide.
Growth form: Grows extremely slowly—only a few inches in its first ten years. Arms usually appear at 60–75 years in Saguaro National Park, up to 100 years in drier areas; some never branch.
Flowers: Creamy white, waxy flowers at the tips of the trunk and arms open at night and close the next afternoon. Plants start blooming at about 35 years.
Flowering time: Late April to early June.
Fruit: Red fruits 2.5–3.5 in (6–9 cm) long ripen in June–July, each with about 2,000 tiny black seeds.

Look-alikes

organ pipe cactusStenocereus thurberi

Organ pipe cactus branches from near the ground into a clump of many columns, with dark green skin and reddish-black spines; saguaro has a single tall trunk with arms higher up.

Why they get mixed upBoth are tall columnar cacti of the Sonoran Desert, and both grow wild in southern Arizona.

cardónPachycereus pringlei

Cardón branches heavily from near the base and blooms along the sides of the stems; saguaro has fewer arms, usually from midway up, with flowers at the tips.

Why they get mixed upBoth are giant columnar cacti, but cardón grows in Baja California and coastal Sonora, not in the US.

Where it lives

Typical habitats: Sonoran Desert
rocky desert slopes
Range: Western Arizona, southeastern California (only about 30 wild plants), and western Sonora, Mexico.
Preferred conditions: From sea level to about 4,500 ft (1,400 m); long freezes limit how far north and how high it grows.
Flowering: Flowers Apr–Jun
Flowers Apr–Jun · Fruit Jun–Jul

Life cycle

Reproduction: Seedlings survive mainly under such as palo verde, ironwood, and mesquite.
Seed dispersal: Many animals eat the fruit, including white-winged doves and ants. Coyotes and cactus wrens pass the seeds through intact and spread them. Of 20–40 million seeds in a lifetime, usually only one or two become adults.

Name and classification

Varieties and forms: About 1 in 10,000 saguaros grows a fan-shaped "crested" top from abnormal growth called .

Conservation

IUCN Red List: LCLeast ConcernLow risk of extinction
Status: Protected by Arizona law: harming one is illegal, cutting one down can be a felony, and moving one requires a permit. Saguaro National Monument near Tucson was proclaimed in 1933 to protect it and became Saguaro National Park in 1994.
Threats: Development around Tucson, and invasive buffelgrass that fuels fires saguaros can't survive. Drought and hard freezes also kill plants.

Culture and stories

Culture and stories: The Tohono O'odham harvest the fruit each June with long poles made of saguaro ribs, cooking it into syrup and jam; fermented fruit wine is part of rain ceremonies.
The genus honors Andrew Carnegie; the O'odham name is Ha:san.
Scar tissue around old woodpecker holes hardens into "saguaro boots," once used as containers.