Carnegiea gigantea (Saguaro)

The Saguaro (Carnegiea gigantea) is an iconic cactus renowned for its towering, tree-like structure. It is characterized by a thick, ribbed, columnar trunk and arms that extend upwards and outwards. Saguaros are among the most recognizable cacti and can live for over 150 years. They are slow growers, often taking up to 75 years to develop their first arm.

Carnegiea gigantea: An In-depth Look

Native: Native to the Sonoran Desert in the U.S. state of Arizona, the Mexican state of Sonora, and a small part of Baja California and California

Plant Type and Habit: Spectacular due to its immense size and unique architecture, Saguaro is a massive columnar cactus with a single, thick green trunk and one or more lateral branches. The Saguaro’s surface is ribbed and covered with protective spines. Its vertical ribs enable the stems to expand as they gain moisture and to contract as they lose moisture.

Size: Saguaro can reach impressive heights, typically 50 feet (15 meters), with a spread of 10 feet (3 meters) determined by the number and length of its arms. When young, Saguaro forms a green, cylindrical solitary columnar stem, up to 10 feet tall (3 meters), with 11-15 stem ribs. It typically branches after reaching 12-15 feet. (3.6-4.5 meters), forming stems with 19-25 shallow, blunt ribs.

Saguaro is, however, extremely slow-growing, adding only 1 foot (30 cm) every 10 years. After 50 years, Saguaro may be 6 feet tall (180 cm). It may sprout its first branches after 75 years. An adult Saguaro is generally considered to be about 125 years of age.

Flowers: From spring to summer, mature plants produce showy white blossoms, 3-5 inches long (8-12 cm), which open in the late afternoon and remain open until the next afternoon. A stem might produce more than 100 flowers at a time. The saguaro flower is the state flower of Arizona.

Fruits: The blossoms give way to egg-shaped, edible, fleshy, green, red to purple fruits with a juicy, sweet, bright red pulp. The fruits are delicious and have been widely gathered for food and wine-making. They are also important for local wildlife.

Foliage: Being a cactus, the Saguaro’s “foliage” is its thick, waxy, green skin, adapted for efficient water storage and photosynthesis.

Uses: Historically, the Saguaro has been used by indigenous peoples for food, water storage, and building materials. Today, it’s primarily a symbol of desert landscapes. Great for desert gardens, rock gardens, or succulent gardens.

Hardiness: Saguaro is hardy in USDA zones 8-11 and is reported to be cold-hardy down to 23°F (-5°C) for short periods.

Wildlife: The cactus provides habitat and food for desert wildlife, including birds, bats, and insects. The hollows in Saguaros are often used as nesting sites.

Toxicity: It is not known to be toxic. In fact, their fruits are edible and nutritious.

Deer and Rabbit: Generally not affected by deer and rabbits due to its spiny surface and height.

Drought: Extremely drought-tolerant, they are adapted to survive in arid environments with infrequent rainfall.

Invasiveness: Not considered invasive. Saguaro is slow-growing and adapted to a specific desert habitat.

Saguaro Growing Tips

Light: Requires full sun exposure, although it appreciates light shade when young. Thrives in bright, direct sunlight for most of the day.

Soil: Well-draining soil is essential. Prefers sandy or gravelly soil types, typical of its native desert habitat. Repotting should be done every other year or when the plant has outgrown its pot.

Water: Minimal water requirements. Overwatering can be harmful. Water infrequently, allowing the soil to dry out completely between waterings.

Fertilizer: Requires little to no fertilization. If needed, use a cactus-specific fertilizer sparingly in the growing season.

Pruning: Pruning is not generally necessary or recommended.

Propagation: Propagated from seeds, although it is a slow and challenging process. Seeds germinate in 7-14 days at 70-80°F (21-27°C). Seedlings should not be disturbed until they are well-rooted. Requires patience as Saguaros grow very slowly.

Pests/Diseases: Susceptible to fungal diseases or root rot from overwatering. Watch for pests like bark beetles or cactus longhorn beetles.

Additional Tips:

• Saguaros are best suited for outdoor growth in the right climate, as indoor conditions rarely meet their needs for light and temperature.
• They are protected species in many areas, so ensure compliance with local regulations when planting.