You probably don’t need to be told again that the summer of 2020 was the hottest summer on record with negligible rain in Fountain Hills. Sadly, many saguaro cacti have met their demise as a result.
The saguaro is one of the most iconic species of the Sonoran Desert. Over millions of years, they have adapted to the harsh conditions of this climate. This was accomplished with a succulent stem that stores a huge amount of water, accordion-like ribs that expand and shrink with fluctuating water levels, leaves that are modified into spines, a thick cuticle for reduction of evaporation, and a metabolism that can withstand long periods of dry weather.
The local monsoon season typically runs from July through mid-September. These life-giving rainstorms eluded us this summer. Monsoons are essential for the saguaro to recover from water loss during the hot summer months. These giants suffer dehydration without these soaking rains.
As a saguaro becomes dehydrated, the stems get thinner and the ribs shrink and become narrow and deep. As a result, the plant may collapse under its own weight.
Saguaros have a shallow root system. It has a taproot that runs 2-3 feet deep and lateral roots to anchor it that only go 1-2 feet deep. When a saguaro is transplanted (as most in our landscapes are), most of the lateral roots are removed, leaving only the short taproot. Often during transplanting, the cactus is planted 1-2 feet deeper than the original depth and the soil is aggressively tamped down to give the plant stability. This is the main reason many fail to establish. The roots are planted too deep for adequate water to reach them. Root rot usually follows.
In summers like this, a saguaro could use an extra drink of water. Make a well around the base of the cactus and run a trickle of water from a garden hose for 4-6 hours. The goal is to get the soil moist to a depth of 2-3 feet where most of the roots are found. This is only necessary once a month during the hottest parts of the summer.
To learn more about saguaro cactus care, check out THIS PUBLICATION from the University of Arizona Cooperative Extension.