One of my Pachycereus pringlei
Found only on the Baja Peninsula and some nearby mainland areas of Mexico, Pachycereus pringlei or "Cardon Cactus" is probably the largest cactus in the world. I have read that some old timers have been measured to a height of 70 feet and as much as 5 feet in diameter! It's reported that some specimens may be 300 years old. Heavily spined while young, P. pringlei loses it's spines as it ages. Eventually the trunk becomes covered with a corky bark and resembles the leg of an elephant, hence one common name, "Elephant Cactus". The plant eventually grows vertical arms similar to our Saguaro. In time these arms can grow even higher than the central trunk.
From early spring to mid summer white nocturnal flowers appear on the sides of the stems facing the sun. Like many cereiods, Pachycereus are mainly pollinated by bats during their northward migration. They produce copious amounts of nectar for them to feed on. When it is time for the bats to move southward again in fall they feed on the ripe fruits and distribute seed in their droppings.
I have two of these. This foot high one which goes in the ground and another smaller one I'll keep potted for a few years.
A view of a spineless stem with flower buds at the Desert Museum