A giant saguaro cactus (Carnegiea gigantean) is a cactus commonly found throughout Arizona and in parts of California and Mexico. It grows outdoors in the Sonoran Desert, but some home gardeners may want to grow a saguaro cactus indoors, especially those who live in an environment that may have cool or even freezing nighttime temperatures, which could damage or kill a saguaro. In order to grow a saguaro for indoor occupation, you need to utilise the proper planting technique and cactus care.
Mix equal parts cactus soil and peat moss together in a large planter.
Fill the planter 3/4 full with the cactus soil and peat moss mixture.
Place the cactus seedling in the planter so that its roots rest on the soil. Then fill more of the cactus soil and peat moss mixture around the roots. You want the cactus' roots to be below the soil, but the seedling's green stem should be above the soil.
Put the planted cactus in a room that is consistently bright throughout the day, but has low humidity.
Water the saguaro seedling whenever the soil dries out completely to the touch. Depending on the conditions in your indoor location, this should be between 10 days and two weeks. Press your fingers into the soil to 4 inches. If you feel any moisture in those first 4 inches, wait a few more days to water until the first 4 inches are completely dry.
Fertilise the cactus just once in the spring with a well-balanced fertiliser.
You can purchase cactus soil at any succulent store and most gardening stores or nurseries. Once the outdoor nighttime temperature falls below 15.6 degrees C, discontinue watering until the temperature rises above 15.6 degrees C again.