Pachycereus pringlei
Pachycereus pringlei, also known as Mexican giant cardon or elephant cactus, is a species of cactus native to northwestern Mexico in the states of Baja California, Baja California Sur, and Sonora. It is commonly known as cardón, a name derived from the Spanish word "cardo", meaning "thistle". Large stands of this cactus still exist, but many have been destroyed as land has been cleared for cultivation in Sonora. The fruit of this cactus was an important food for the Seri people in Sonora, who call the cactus "xaasj". A symbiotic relationship with bacterial and fungal colonies on its  roots allows "P. pringlei" to grow on bare rock even where no soil is available at all, as the bacteria can fix nitrogen from the air and break down the rock to produce nutrients. The cactus even packages symbiotic bacteria within its seeds. Morphology. A cardon specimen is the tallest living cactus in the world, with a maximum recorded height of , with a stout trunk up to in diameter bearing several erect branches. In overall appearance, it resembles the related saguaro ("Carnegiea gigantea"), but differs in being more heavily branched and having branching nearer the base of the stem, fewer  ribs on the stems, blossoms located lower along the stem, differences in areoles and spination, and spinier fruit. Its flowers are white, large, nocturnal, and appear along the ribs as opposed to only apices of the stems. Lifespan and growth. An average mature cardon may reach a height of , but individuals as tall as are known. It is a slow-growing plant with a lifespan measured in hundreds of years, but growth can be significantly enhanced in its initial stages by inoculation with plant growth-promoting bacteria such as "Azospirillum" species. Most adult cardon have several side branches that may  be as massive as the trunk. The resulting tree may attain a weight of 25 tons.