Arizona sunrise with a Harris’s Hawk on an ancient Saguaro Cactus. Check out these crazy Saguaro facts! It takes a decade for a Saguaro seedling to reach the height of just two inches. They don’t begin to flower until they’re 40 to 60 years old, don’t develop their first arm until 70, and only reach full maturity at around 125. This strategy of slow growth has allowed Saguaros to survive long dry spells and live for 200 years and up. A healthy adult saguaro produces about 100 enormous white blos