Plants native to the Sonoran Desert require watering every 6 months. The following perennial plant, which I am not sure is native to the Sonoran Desert, was found to thrive in the Sonoran Desert solely off rain. What is this plant?
This appears to be Mexican Petunia (Ruellia simplex). Should eventually have small, blue/purple petunia-like trumpet shaped flowers. The plant I have pictured has not been grown in desert climates.