The Saguaro Cactus Abiotic Needs & Abiotic Interactions

Water and Soil

• Although saguaros live in the dry desert, they consist largely of water. Saguaros grow up to 50 feet tall and weight 6 tons, so they require a lot of water. Shallow saguaro roots radiate out from the cactus to soak up all precipitation. The cactus skeleton is a circular set of woody ribs that expand and contract as water is absorbed and depleted. Well-drained soil permits the water to penetrate to the roots. Soggy soil may prevent the roots from maintaining the cactus upright.

Drought

• Drought and high temperatures result in many cactus deaths. Although adult cacti store sufficient water to flower and fruit regardless of rainfall, young cacti die from lack of water, especially during high temperatures. Each saguaro produces some 400 million seeds during its long lifespan; few of these grow and even fewer live to adult age, considered to be 125 years for saguaro. The top cause of cactus shoot fatalities is inadequate water.

Light and Temperature

• The Sonora Desert offers extreme amounts of sunshine, as well as the above-freezing temperatures saguaros require. On an annual basis, almost nine out of every 10 days offers full sun in southern Arizona. This sunlight is necessary for the saguaro's photosynthesis. On the other hand, sunlight combined with high temperatures can impede the saguaro. For this reason, young saguaro shoots grow beneath the shade of a nurse tree, and the saguaro's creamy flowers only open in the cool of the night air.

Temperature and Elevation

• Although saguaros tolerate a wide range of temperatures on the Sonora Desert -- from over 100 degrees in the summer sun to around 38 degrees during winter nights -- freezing temperatures maim or kill them. When a section of a saguaro freezes, it can kill the entire cactus. Saguaros grow generally between sea level and 4,000 feet elevation. Since heat drops with elevation, however, saguaros in the upper elevations only thrive on the south-facing mountain slopes.