The saguaro cactus (Carnegiea gigantiea) is one of the defining plants of the Sonoran Desert. These plants are large, tree-like columnar cacti that develop branches (or arms) as they age. These arms generally bend upward and can number over 25. Saguaros are covered with protective spines, white flowers in the late spring, and red fruit in summer. They are found exclusively in the Sonoran Desert. The most important factors for growth are water and temperature. If the elevation is too high, the cold weather and frost can kill the saguaro. Although the Sonoran Desert experiences both winter and summer rains, it is thought that the Saguaro obtains most of its moisture during the summer rainy season.
You find this cactus in southern Arizona and western Sonora, Mexico. At the northern portion of their range they are more plentiful on the warmer south facing slopes. A few stray plants can also be found in southeast California. It is estimated that saguaros can live to be as much as 150-200 years old. The saguaro is the largest cactus in the United States. Most of the saguaros roots are only 4-6 inches deep and radiate out as far from the plant as it is tall. There is one deep root, or tap root that extends down into the ground more than 2 feet.
Plants are treelike, reaching heights up to 52 feet (16m) with stems up to 30 inches (75cm) in diameter. Branches begin forming on larger plants at around 7 to 9 feet (2.2 to 2.7m) when they are decades old. Ribs are straight and may be narrow or broad depending on the amount of moisture stored in the tissue. Numbering from 12-30 and 1 to 1 1/2inches tall (2.5 to 3.8cm). Areoles, white-grey, are close together within 1/2inch (12mm). Spines are golden-brown to grey from 1 to 1 1/2 inches (2.5 - 3.8 cm). Spines are unequal in length, with one prominent central spine per areole that is distinctly pointed downward - a useful identification key. Flowers form near the apex of the stem or 6 to 12 inches (15 to 30 cm) below the tip. Flowers are waxy white, bell shaped and are 2 to 2 1/2 inches (5 to 6.25 cm) in diameter and approx. 5 inches (13cm) long. Flowers are fragrant, mildly sweet-smelling and are open during the day and night lasting 1 to 2 days. Floral tubes are green with scales. Fruits are green, turning red as they ripen and are soft and edible. Fruits break open on the stem as they ripen exposing a dark-red pulp containing dozens of 2mm black seeds.
Native Americans made use of the entire cactus: they ate the fruit both fresh and dried and made it into preserves and beverages; the framework of ribs provided wood for shelters, fences, and kindling. It is the state flower of Arizona and a symbol of desert landscapes. Well-adapted to its hot, dry climate, Giant Saguaro is leafless. Food is manufactured in the green stems, and rainwater is absorbed quickly by the shallow roots and stored in the succulent trunks and branches. The thick, spreading spines offer protection against animals. Gila woodpeckers and gilded flickers make round holes near the tops of branches for nests that are used afterwards by elf owls, cactus wrens, and other birds. Wildlife, especially white-winged doves, consume quantities of the seeds.
- The seeds like sandy, well-drained soil. Fill a pot with moist cactus mix or used a mixture of sand and peat moss, perlite or vermiculite. Use a pot that has drainage holes in the bottom.
- Sow the seeds on the surface of the soil.
- Cover the seeds with a thin layer of soil.
- Water the soil with a mister or by placing the pot in a saucer of water. The soil will absorb the water.
- Place the pots in an area with warm temperatures in indirect sun or part shade. The seeds germinate in a few days. Do not overwater the plants.
- When the seedlings are a few inches tall, they can be transplanted.