Trivia: What species is the tallest cactus ever measured?
Cholla
Saguaro
Prickly pear
Joshua tree
The correct answer is Saguaro
So why is this answer correct? : Although the Mexican giant cardon is generally considered the largest cactus species in the world, the largest single cactus is a 78-foot-tall saguaro cactus. Unlike other plants, saguaros are particularly slow growing — it can take a decade for the plants to reach 1 inch tall.