Carnegiea gigantea aka Saguaro Cactus

Carnegiea gigantea, or saguaro, is a tall, tree-like cactus. It belongs to the cactus family, Cactaceae. Its native range spans southeast California, southern Arizona, and northern Mexico. It grows in the Sonoran Desert on slopes and plains. These sites have dry, rocky or sandy soil that drains well. Young plants often start life beneath shrubs or trees. These nurse plants shelter them during their early growth.

The plant forms one thick column before growing upright arms. These branches may not appear for 50–75 years. Sources give usual heights near 30–33 feet [9–10 metres]. Oregon State reports growth to 50 feet [15 metres]. Exceptional plants reach about 52 feet [16 metres]. The trunk can reach 2.5 feet [0.75 metres] across. Thick green skin covers the trunk and its raised ribs. Clusters of stiff spines line these ribs in vertical rows. Growth is slow, even when gardeners raise plants in pots.

White flowers with yellow centres grow around the branch tips. They open at night during May and June. Each flower lasts less than a day. Bats visit at night; bees and birds visit by day. The plant cannot fertilise itself. Its oblong fruits ripen in June and July. They turn from green toward red, then split open. Each fruit holds red flesh and many small, dark seeds. Coyotes, peccaries, and doves help spread the seeds.

Grow saguaro in sun and soil that drains freely. Keep young seedlings out of full sun. Established outdoor plants need no extra water, according to Oregon State. Potted plants need summer watering, with full drying between waterings. LLIFLE advises keeping them dry through winter. Damp pots can cause root loss. Too much water and shade can distort growth. Hot summers and mild winters suit this cactus best. Oregon State lists it as hardy to USDA zone 9. It can survive brief cold near 23°F, but prolonged freezing kills it.

Gardeners grow saguaro for its tall form and upright arms. Birds dig nest holes into its flesh. Dead woody ribs have served as building material. People also make vessels from the hard linings of old nest holes. The fruit is edible fresh, cooked, or dried. People make juice, syrup, jam, wine, and vinegar from it. The seeds provide food rich in oil and protein. Useful Tropical Plants lists no known hazards. It reports Least Concern status, though building development threatens populations.